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My Retro-ish Carbine Build and Griffin Armament XM Linear Comp
8/28/15 - I recently decided to built a retro-ish carbine when I discovered some old parts I had stored away. Around the same time (and unbeknownst to me), Griffin Armament was working on their XM Linear Comp; a clone of the original XM moderator found on the XM177 series of Vietnam-era weapons. Here's how it came together.
A little personal background - I've been drawn to the M16 ever since I was a kid (as well as the FN FAL/L1A1 when I saw British soldiers with it - I spent the first part of my childhood in England). I bought my first AR in 1985; it was a Colt AR-15A2 Sporter II (R6500) with the round handguards and A1 rear sight. When the movie 'Platoon' came out in 1986, I did know enough about the Vietnam era carbines to know that the ones depicted in Platoon were incorrect, as the model 653 carbines SSG Elias and Barnes carried were not used in the Vietnam war, and were probably meant to be XM177E1 or XM177E2 carbines. Even so, I just had to have a carbine, so I saved my money up and looked out for them at the local gun shows. I eventually found a guy selling a used Colt R6001/SP1 Carbine, circa 1979-80 based on serial number, but it had a nylon stock instead of an aluminum one. I bought it anyway, and I shot and carried that thing around lot when my high-school/college buddies and I went hiking/camping in the mountains.
The years went by, and 'standard' carry handle rifles/carbines were no longer 'cool' when the flat tops and M4s came out. No one wanted a fixed carry handle upper with A1 sights, especially one with a pencil barrel. Heavy barrels were the rage. I ended up taking it apart and eventually updating it with a KAC MRE rail, flat top upper receiver and other components. The A1 upper receiver and some other parts ended up in a box somewhere in the garage, pretty much forgotten.
While there have always been collectors of rare or old firearms, it wasn't until about 10 years ago that I noticed people starting to get interested in retro black rifles. It seemed that 'retro' meant anything before the AR15 A2 came out - basically M16A1 and earlier. I watched as the interest grew, as did the incredible amount of information available on sites such as retroblackrifle.com. But, I focused my attention on new weapons instead, watching the AR15 evolve into the 'space age'-looking whizz-bang ARs we have nowadays. I looked forward, not back. Until...
Deciding to go back - A few months ago, I was digging through an old parts box when I came across some of my old Colt A1 Carbine parts - Colt 'N' marked nylon stock, upper receiver, non-tapered slip ring and barrel nut and handguards. I thought to myself "Hey, I've actually got almost enough parts to put together a simple retro-ish carbine." My lower receiver and original barrel were tied up in the other build, and spray painted in camouflage paint, so I wasn't going to touch them. I had enough spare parts to put together a complete rifle except for the barrel. Now, there are guys who build retro clones, which are almost exact replicas of original models. They use original parts if they can. That can be very expensive and can take years to find the right part. Then there are those that use replica/repro parts to create something that looks visually correct. What I wanted to create, however, was a modern carbine (except for the sights) that had the 'essence' of a retro carbine - not necessarily looking correct, but not looking like a brand new carry-handle carbine either. I didn't want to spend much, as this would be just a fun rifle to shoot.
My build - Since I had a slick-side (no forward assist) Colt A1 upper, my carbine build was more similar to the Air Force GAU-5A (model 630) than the XM177E2 (model 629). Also, I had decided that I was going to make this rifle with ambi controls; even though they were anachronistic and inaccurate for a true retro build. Here's my main parts list:
Tony's Custom Barrel - When I received the barrel, I was pleasantly surprised. Instead of the .750" barrel shown on the website, the barrel that came was a more correct .625" diameter light weight. My happiness turned to disappointment as I noticed that a triangular handguard cap had been assembled on it, instead of the correct round handguard cap. I couldn't use it in that configuration. I called Tony's and they told me to ship it back. I did, at my expense. After a couple of weeks, I received a replacement barrel. Unfortunately, it was a heavier .750" barrel, but this time with the correct round handguard cap. I decided to just use it. I also cut off the bayonet lug since XMs didn't have them.
Re-finishing the lower - Since I was using a Bushmaster lower, which was anodized black, I wanted to have it match the grey Colt upper a little better. I was not going to send it out to get it re-anodized as this was a project on a budget, plus I wouldn't have wasted that on an incorrect lower anyway. I bought some dark grey auto primer, filled in the Bushmaster snake logo with epoxy, painted the lower, then put a few matte clearcoats over it. I also did a bit of 'weathering/ wear', to match my A1 upper. Even though it was closer to the newer Colt dark grey, it actually turned out quite nicely. I also painted the black Vltor receiver extension in the same manner and the charging handle.
Ambi/Modern parts - Since I'm a lefty, I installed an ambi safety, Norgon Ambi-catch, and 1st generation Badger Ordnance Ambi charging handle. The Badger Ordnance Ambi charging handle looks exactly like the USGI charging handle, with the addition of a latch on the right side, so it's not obtrusive at all and looks at home on a retro weapon. I weathered each item to match the upper. Just a little bit of rubbing with a Scotchbrite pad and fine sandpaper in the right spots did it. I used a modern castle nut vs. the old lock nut with pin hole because they were such a pain. I also used a BCM receiver end plate with QD swivel socket in case I wanted to use a sling in that location. I stuck a stock trigger in the lower. I also used an Oberland Arms trigger guard which is much more comfortable when handling the rifle with one hand; the USGI trigger guard tends to be rather sharp. I also de-horned the trigger guard 'ears' on the lower to remove sharp edges. While none of these parts belong on a true retro clone, they're worn to match the upper and 'look the part'.
The end result is shown below. Retro-ish, but immediately suspect because of the .750 barrel and flash hider to anyone who knows what they're looking for (besides all the ambi stuff of course). Except that this wasn't the 'end'.
Griffin Armament XM Linear Comp - A few weeks before I completed the above build, and after I had already ordered the Tony's Custom XM barrel, I saw a picture of an XM lower being marked on the Griffin Armament facebook page. Curious, I emailed Austin Green about that project, and he also informed me that he had been building XM177E2 replicas for him and his brother, and also working on an XM Linear Comp, which was to be an exact external replica of an original XM moderator. Now, when doing my research for this build, I found out that accurate-looking XM moderator replicas are hard to find. There are some individuals making them, but you can't just order them off a website and get them in your hands in a couple of days. Also, the original XM moderators were around 4.5" long, which means that you have to get an SBR tax stamp if you mount it on the correct 11.5" barrel, or get a longer barrel, cut it down, then permanently attach it to the muzzle. The longer 5.5" flash hiders from Bushmaster for the 'XM look' were typically too skinny, and weren't the correct shape. Same thing for the slip-over flash hiders, that slipped over the end of a 16" barrel. They just didn't look right. The Tony's flash hider attempted to simulate the moderator with grenade ring, but only half-heartedly.
Not very satisfied with the .750" Tony's barrel and faux XM moderator, I asked Austin if he'd help me if I got another barrel to him to mount his XM Linear Comp to as a favour. He agreed, and I ordered a 16" Colt 1/7" twist, .625" lightweight/pencil barrel from Brownells and had it sent directly to Griffin. Austin cut it down to 12.37" for a 16.1" total length with XM Linear Comp.
Background - As Austin explained, he and his brother Evan had wanted to make XM177E2 clones for years. The rifles have legendary status on account of their MACV-SOG, Ranger, LRRP and SEAL use In Vietnam. They only needed two for themselves, but decided to make a run of them since they were being manufactured on CNC equipment. The XM Linear Comps follow the original blueprint dimensions externally, including a grenade ring made to original tolerances with one additional feature - a .025" chamfer on the .630" diameter of both parts so that modern barrel thread runout can be accomodated. The Vietnam era Colt barrel thread profile tool had zero radius whereas modern barrel have a 1/64" radius at the shoulder so original grenade rings may not sit square on modern barrels.
The original XM Moderator was classified by the BATF as a suppressor because it contained a series of baffles in an attempt to reduce the ear-splitting report of an 11.5" barrel. Real XM Moderators are therefore NFA items requiring the same tax stamp as any other suppressor, except that they suck as suppressors. The Griffin XM Linear Comp is hollow internally like their M4SD Linear Comp. It's actually a functional muzzle device rather than just a tube to simulate an XM moderator. Since it has a chamber and a small opening and cone just aft of the flash hider slots, the chamber helps increase back pressure to simulate a longer barrel and aid in cycling on short barrels. It also directs noise and concussion forward of the shooter.
The original XM moderators had a weld line near the rear of the body. This was one of the aesthetic challenges of the XM Linear Comp project; what to do regarding welds. The difference externally between the print and the actual part was based on the welding process and how the melted metal altered the signature of that area of the part. Post war production and actual Wartime production samples differed with post war welding being a lot colder and at times looking a lot more refined than actual wartime production welds. Some wartime examples featured very hot welds that burned the .0625" radius nearly completely off the back of the housing. Griffin ended up locating an XM moderator traceable to actual MACV-SOG issue and based the "weld" geometry off that actual part.
The XM Linear comp dimensions are based on a blend of the original Colt prints and the actual example XM moderator and grenade ring they had in hand. It's externally very close to the original moderator. The flash suppressor slots are curved, however, instead of angular as on the original moderator. The wrench flats require either a thin wrench or an M16A1 armorers tool for installation.
Also, faced with the decision to consider making an NFA moderator with original style internal baffles, Griffin decided that a non-NFA device not intended for sound reduction that didn't require a $200 tax stamp would be more practical. The $200 tax is prohibitive to most people when it's not for the purchase of a real, effective, sound suppressor. The Linear comp would still be as useful a muzzle device without resorting to the original miniature sound suppressor design, or changing the external appearance with features designed to reduce muzzle climb. Griffin could have made it cheaper without designing it as a linear compensator and without having a lot of technical machining for material removal. However, they didn't want to make a device that looked correct but was nothing but a large barrel weight. They wanted the XM Linear Comp to be a great option for people who wanted a correctly dimensioned XM muzzle device for a retro build that was also functional for shooting.
The XM Linear Comp is made of 17-4 PH stainless steel, which provided design flexibility as it is 30-40% stronger than 4140. Instead of a black oxide finish, it's finished in black melonite. However, with a few swipes of a Scotchbrite pad, it looks indistinguishable from well worn parkerizing.
The specs on the XM Linear Comp are:
Installation - The sample XM moderator that Griffin studied had one slightly deformed slot. They were told that the MACV-SOG guys used their knives to tighten and remove moderators. This made sense since the Colt engineer made the wrench flats too narrow for a standard wrench. The XM177 manual showed no lock washer and called for 15-20ft lbs of torque, which as a suppressor manufacturer, Griffin knew that wasn't sufficient to retain a suppressor-like muzzle device when hot, so tightening the unit to 30-35 lbs more made sense. Tightening more than specified in the manual would have been required for confidence. The .625" wrench flats fit the standard M16A1 barrel extension wrench. The XM Linear Comp does not have to be timed.
The grenade ring is stepped internally, forming concentric rings with different diameters. The hole itself measures .52" in diameter, and the next step is .626" to slip over a .625" diameter barrel. The last step measures .750" diameter. Total thickness of the grenade ring is .320" with the thickness of the last step measuring .09".
Colt Barrel - Shown below is the new Colt barrel cut down to 12.37" for a 16.1" total length with pinned/welded XM Linear Comp and bayonet lug removed. I had disassembled the Tony's Custom barrel from my Colt A1 upper and replaced it with the Colt barrel when I got it from Griffin. I used my A1 non-tapered handguard slip ring simply because it was 'moar retro' than the delta ring.
Griffin Armament SOB (Suppressor Optimized Buffer) - Another component that Griffin introduced at the time of this build was their AR-SOB (Suppressor Optimized Buffer). Most low-end rifles are aggressively overgassed, and supplied with cheap, light CAR buffers which are employed to reduce system cost, robbing rifles of necessary weight for reliable chambering with fouled chambers, and encouraging premature unlocking of the bolt, causing undue extraction stress. This contributes to operational and mechanical failures of critical system components. Suppressors further increase system operating speed and exacerbate the over-gassed condition. An AR-SOB will work to resolve these issues by allowing a carbine to run similarly to the original product improved M-16A1 "Sturtevant" rifle length buffer, despite the reduced internal length of the CAR receiver extension.
Paraphrased from Griffin's website - The SOB built from 9 individual components and is a staggered impact, dual urethane buffered design. Utilizing non reciprocal weight and reciprocal weight similar to the A2 rifle length buffer, in conjunction with shock dampening brass weights, the AR-SOB offers increased system dwell time, reduced bolt speed, and enhanced chambering reliability. Through integration of a shorter platter of CNC machined weights and a telescoping buffer head, the AR-SOB has 30-50% tighter tolerances, allowing precisely controlled timing and forced sequential impact of buffer weights interacting with the rifle's operating system. The SOB weighs 4.9 ounces, and can be used in suppressed 5.56mm rifles as a replacement for the M4 carbine series buffers, and also in .308 carbines as a replacement for H2 and H3 buffers when used in conjunction with the AR10 mil-spec CAR receiver extension and AR10 CAR action spring.
Theory of Operation - I asked Griffin how the SOB worked, and they explained it as so: Internally, the SOB has 2 sliding CAR style weights and rubber discs. The operating theory behind the SOB is that a standard carbine buffer's 3 internal weights do not actually interact out of phase with each other, even though the buffers' designer's intent was to have a "cascading" impact of weights. In the carbine buffer, the weights move all together (simultaneously) , or very nearly so; as opposed to the rifle buffer with its 5 weights and discs and tube spacer weight, which are much more likely to cascade. The timing of the impact in the carbine buffer is less than optimal as well, due to tolerance stack up in free travel and compartment length, all 3 weights and rubber discs thickness. When they move in tandem, that travel is about .034"-.04" too long to be optimal. When seen on camera, the bolt (carrier) bounce is reduced but not eliminated with the H2 buffer. The bolt carrier rebound occurs before the weights can complete travel and impact. Bolt bounce only really affects full auto fire; not semi-automatic fire (unless you are cycling the trigger extremely fast, as in some double-taps).
The head of the SOB buffer moves in and out a small amount from the buffer body. There is a polyurethane washer (same material as the buffer end) between the buffer head and body so that weighted impact is dampened. By disconnecting the buffer head from the buffer body and controlling its travel using a CNC machined slot and pin, the SOB is able to better control the timing of the impacts of weights, such that there are 2 impacts- the buffer body which is itself a weight, and the sliding weight inside the buffer body. There is also about .015-.02" less extra space required in the sliding compartment, by getting rid of a rubber disc and sliding weight. The head is timed to impact within .055" of bolt closure, whereas the standard carbine buffer has about .120" of travel. By providing a more 'dead-blow' operation that lessens bolt bounce; operation should be smoother, and reliability improved.
The head of the SOB buffer is very nearly the same weight of the non-reciprocating components in the A2 rifle buffer. Likewise, the reciprocating weight nearly mirrors that of the rifle buffer. The goal is to provide a more rifle-like buffer operation in a carbine system. Suppressors are always going to overgas a weapon, so the 4.9 ounce weight of the SOB is good for use with suppressors. The SOB buffer can be used as an H2 / H3 replacement as well. Note that heavy buffers don't work in all platforms.However, where there is enough gas to drive them, they should provide better reliability.
Some of the key features of the Griffin Armament SOB are:
Other parts - I bought some new parts for the Colt/Griffin upper. I bought a 'slick side' chromed (no forward assist notches) carrier from Fulton Armory, which is again incorrect for use on a GAU, and found on the early rifles, but this was my 're-imagined' carbine and I needed an extra bolt carrier anyway. It made sense to have a slick side carrier for a slick side upper with no forward assist. I also replaced the front sight with a narrower National Match .050" A2 front sight post, and the rear sight with the standard A2 (large and small apertures) instead of the A1 that had two small apertures. I also replaced the USGI trigger and hammer with a Hiperfire Hipertouch EDT (Enhanced Duty Trigger), which is a relatively inexpensive drop-in trigger, that's an improvement over the stock trigger.
Fnished re-imagined "GAU-5A" rifle - The finished build of my ambi GAU-5A carbine is shown below. The only major difference between that and the previous incarnation is the Colt barrel, and upgraded internal parts. I'm really pleased with the outcome and it's going to be my constant range companion, along with my newer carbines. Weight of the rifle in this configuration (empty) is right on the dot at 6 lbs.
Re-imagined "XM177E2" upper build - So, I had the spare Tony's Custom barrel sitting around, since I had replaced it on my Colt A1 upper with the Colt/Griffin barrel. Rather than let it go to waste, I decided to put together another 'retro-ish' upper with it. This time, I got a C7 upper receiver. The C7 is the Canadian version of the M16, and the earliest version had the same fixed carry handle and A1 sight as the M16A1, but with the addition of a shell deflector on the receiver. Since I'm a lefty, I wanted one retro upper with a shell deflector, just in case the A1 upper with no shell deflector resulted in my face getting hit by empties. I used a standard bolt carrier in this upper, instead of the chrome slick-side since it has a forward assist.
I picked up a used C7 upper with EK (EMCO/Kaiser) forge mark. Since it was finished in black, I refinished it in the auto gray primer to match my painted lower and gave it the same type of wear. I also used a tapered delta ring on it. I also dremeled a new teardrop forward assist to match the smoother edges of the earlier versions. This configuration (with the exception of the shell deflector and wrong barrel) is that of an XM177E2 (Colt Model 629). It's my re-imagined version of course. Total weight of the rifle (empty) is 6 lbs 3 oz.
Notes/Observations - It's been a while since I used a rifle without optics, and I definitely see the advantage to having a red dot or magnified optic. When I got my first AR15, I used the irons, but my eyesight (though already bad) was better then, than it is now, 30 years later. While my eyesight with corrective lenses is fine, I'm not always looking through 'sweet spot' in the lens due to different head/shooting positions. This, combined with astigmatism, makes it difficult to focus clearly on the front sight. Even with handgun shooting now. I do not get the crisp, clear sight picture that I used to in my younger days. All that being said, I found it good to get used to irons again, and while my accuracy and speed suffers a bit in drills, my fun level doesn't. The narrower NMA2 front sight post does help me place it in the center of targets better than the wider standard front sight post.
Another thing to get used to after shooting midlength and rifle-length handguards with vertical grips/hand stops for so long is going back to a short carbine handguard with the support hand closer to the receiver. I do notice that keeping the muzzle on target or transitioning is a little easier with longer handguards, but not by much. The carbine does feel very handy, though, with the lack of anything mounted to the front. Doing drills with 20-round magazines is made easier with shorter, open-top pouches like the EMDOM IAP; otherwise the 20-rounders are hard to extract from deeper pouches designed for the longer 30-round magazines.
The Griffin XM Linear Comp doesn't reduce recoil or muzzle jump (it's not supposed to) but it really reduces concussion and noise to the shooter, directing it downrange instead. This was very apparent when I shot it and compared it to the Tony's Custom barrel with the hollow/open faux moderator. Also, I mentioned this above, but retro builders need not worry about the black Melonite finish not matching their rifles. It's more of a dark grey than black, and with just a bit of buffing/wear takes on the appearance of a worn parkerized part.
At a recent range session, I brought along two rifles, including the GAU-5A. I swaped back and forth between the SOB buffer and an H buffer during drills, and I could feel a noticeable difference in the recoil impulse. The SOB buffer felt softer/smoother and not as snappy; a definite improvement in feel, I thought. The other rifle was a midlength light weight upper with a muzzle brake, and I could also feel the difference between the SOB and the H buffer in it. I didn't experience any malfunctions with either upper, with either the SOB or H buffer. One thing that I was worried about was getting hit in the face by brass when shooting the A1 upper without shell deflector. However, cases ejected around 2:30-3 o'clock and I didn't get a single case in the face.
With just about everyone sporting the latest and greatest ARs and rails, an 'old-school' carbine like this ironically attracts more attention and interest. I know that my wear job on the rifle looks pretty 'legit' because folks will comment 'that thing looks old!', while those who know what they're looking at will say 'that's a cool build, man!', as I explain my parts choices and overall goal of the project (retro-looking but modern in function). Best of all, it's a great conversation starter as people talk about their first ARs 'back in the day', and this will immediately take them back to days when (shooting) life was simpler.
Griffin Armament Hammer Comp and Paladin Brake
9/11/15 - Featured here are the M4SD Hammer Comp and M4SD Paladin Brake from Griffin Armament; two of their shorter muzzle devices. The Hammer is a slotted comp while the Paladin is a single-port brake.
The Hammer Comp and Paladin Brake and most of the other Griffin muzzle devices are designed to be compatible with their M4SD Suppressor, or QD Blast Shield device, which utilizes their 'snap on' attachment. They come with a black tabbed washer and shim kit, for timing the comp.
The specs on the Hammer Comp and Paladin Brake are:
M4SD Hammer Comp - The M4SD Hammer Comp is one of Griffin's shorter muzzle devices at 1.75" OAL; the same length as their original M4SD Tactical Compensator. It provides two sacrificial baffles that extend the life of a suppressor, and help reduce felt recoil. There are four slots of equal size, with the ports biased towards the top of the comp to reduce muzzle jump. The bottom is closed, and has a laser marked Griffin logo on it. The muzzle end has a distinctive exit with three mutually tangential circles. Note that it does not have a pre-drilled pin hole for pinning/welding for permanent attachment to the muzzle.
M4SD Paladin Brake - The Paladin Brake is a compact, single port brake with three top rise-mitigating ports for flat shooting performance. It can be considered a shorter version of Griffin's dual port M4SD Muzzle Brake. Like the Hammer Comp, it's designed to be compatible with their M4SD Suppressor, or QD Blast Shield device, which utilizes their 'snap on' attachment. It also shared the same "triple tangential circle" exit at the muzzle end. It functions as a sacrificial baffle when used with their SD sound suppressors. There is no pre-drilled pin hole for permanent attachment.
Installation - The Hammer Comp and Paladin Brake both include a shim kit, which includes stainless steel shims of two different thicknesses; .002" and .010" thick. Combining shims allows the user to achieve the correct clocking of the muzzle device. If a suppressor or other Griffin QD muzzle device is to be used with the Flash Comp, the overtravel washer should be used. The overtravel washer is first installed on a clean muzzle, then the muzzle device is threaded on hand tight. Noting the orientation of the muzzle device, shims are added behind the overtravel washer to place the top of the muzzle device at about 2-3 o'clock hand tight. A torque wrench is then used to tighten it, keeping the overtravel stop at 6 o'clock. The torque spec is about 30 ft-lbs. The overtravel washer isn't needed if no QD muzzle devices are going to be used.
Notes/Observations - I brought along both muzzle devices to the range with me, swapping them as fast as I could to see what the difference was. Concussion to the shooter (me) felt similar; too small of a difference to give one the edge over the other. When standing about 6 feet to the side, the Paladin's blast felt a bit sharper, which is what I'd expect from a single port device. Muzzle movement reduction and recoil impulse were very close; with a slight edge going to the Paladin Brake, I felt. Both do an excellent job at assisting me keep the dot closer on target (at closer ranges) with a straight-back recoil push. I was shooting in bright sunlight so I did not get a chance to compare the flash signature. I asked Griffin about the differences between the two and they said that the Hammer Comp is better than the Paladin Brake at reducing flash; so that's the main difference between the two devices. That's usually the case with large port comps; so the shooter needs to decide on what has priority - flash reduction or compensation.
Super Tricon Trigger from Geissele Automatics
9/30/15 - The Super TRICON Trigger from Geissele Automatics is a non-adjustable combat trigger based on Geissele's proven SSA trigger. It has a unique trigger bow profile that was recommended by Jeff Gonzales of Trident Concepts.
Geissele Automatics - Geissele Automatics probably needs no introduction to my readers, but on the slim chance you're not entirely familiar with them, I'm including this short profile. Geissele Automatics is a name synonymous with the best triggers for the AR15 rifle. Geissele Automatics was started by Bill Geissele (pronounced 'Guys-Lee') in 2004 as a manufacturer of trigger mechanisms for the AR15 rifle. Their first trigger, the Hi-Speed National Match, was designed for CMP and NRA Hi-Power competition. Since then, Geissele Automatics has expanded their line of triggers to include variants for the military, LE and civilian shooter alike. They have also branched out beyond the AR15 platform and now offer triggers for weapons like the SCAR, AK and IWI Tavor.
Trident Concepts (TRICON) - Trident Concepts, LLC was started by former Navy SEAL Jeff Gonzales, who heads up their staff of diverse trainers and instructors. TRICON provides their clients with a full spectrum of weapons and tactics training, and strives to ensure that the client comes away from a training class not only better educated, but with measureably improved performance. Jeff and I had been corresponding occasionally since 2010 about gear-related stuff, and I finally met him at the 2011 SHOT Show. I had known of him from the old Diamondback Tactical catalogs where he had been featured as one of their training cadre/consultants. I met him again at one of his classes hosted by Alias Training & Security Services this past June and got the chance to spend some good face time with him. This is also where I learned about the Super T trigger.
'Super T' trigger - The 'Super T' trigger came out in 2013, after Jeff had suggested the idea to Bill Geissele with a simple sketch at the SHOT Show. The Super T is a variant of Geissele's popular SSA (Super Semi-Automatic) trigger, which is a 2-stage trigger designed for military/LE or home defense. The SSA is the semi-automatic version of the SSF (Super Select-Fire) which was designed specifically for USSOCOM. The SSA is designed to be a combat trigger that offers both performance and safety (a patented secondary safety sear that prevents the hammer from falling unless the trigger is pulled). The Super T/SSA is a non-adjustable combat trigger; not a match trigger, with a 'carrot-like' break. It is intended for CQB and mid-range carbine work, or for use on an SDM (Squad Designated Marksman) rifle.
The main difference between the SSA and the Super T is the unique trigger bow profile, which starts out with the standard curve of the USGI trigger, but then straightens out. The face of the bow is curved like an M4 trigger but has vertical grooves for added tactility/feel and traction when wearing wet gloves. The reason for this profile is to keep the trigger finger nearer the bottom of the trigger bow, where it has the most mechanical advantage, and also to facilitate more consistent trigger finger placement.
The mechanical features of the Super T are as follows:
The perfomance and safety advantages are:
The Super T trigger comes packaged in a simple zip-loc plastic back with a tiny vial of trigger maintenance grease, hammer/trigger pins, and the disconnector/trigger assembly held together by a slave pin. The slave pin greatly aids in the easy assembly of the trigger.
Installation - If you're familiar with the standard AR15 fie control group, then installation of the Super T will take less than 5 minutes. The safety selector does not have to be removed from the lower receiver, but it must be in the FIRE position during installation. The trigger is installed first; with the slave pin pressed out by the trigger pin once the holes are lined up in the receiver. The hammer is then installed just like the USGI one. After installation, a function/safety check should always be performed. Detailed installation instructions are on Geiselle's website.
I already had a couple of Geissele triggers installed in my rifles, so I've pictured them below just for reference. One is an older SSA, before they went to laser markings (some earlier ones were just scribed marked) and the other is a SD-3G with flat trigger bow.
Technical Details - Just a bit of terminology - a 'single stage trigger' like the USGI trigger, typically means that you increase pressure on the trigger, moving through the mechanical sear engagement travel until the hammer is released. With a two stage trigger, there are two distinct stages of travel; the first is usually overcoming spring tension and the second is the mechanical resistance of the sear movement. By 'sear', I'm referring to the engagement surface between the hammer and trigger than holds the hammer cocked until it's released.
The problem with light single-stage triggers is that they can rely on reduced hammer spring strength and reduced sear engagement, which also reduces reliability (ignition) and safety. The USGI trigger is heavy to retain reliability and safety at the cost of a predictable and smooth pull. By having a two-stage trigger, reliability and safety can be retained while offering the shooter a lighter, crisper and more predictable release of the hammer. It allows the shooter to take up most of the rearward travel (slack) of the trigger until it reaches the second stage, then increasing the force releases the hammer. There's a distinct point between the first and second stage. The SD-3G I use on the range is a very fast trigger, but recommended only for competition or range use only. Choosing between a single stage or two stage trigger boils down to usage and personal preference.
On a typical USGI AR15 trigger, the sear surface is located at the very front of the trigger, at the top, where it engages sear surface on the hammer. On Geissele triggers, this is not the sear. The Geissele trigger has an additional hook that protrudes from the trigger; right above the trigger bow/pivot hole. This backward-facing hook engages the bottom hook on the back of the hammer. This is the hammer/trigger engagement surface on the SSA or Super T trigger. Having the sear engagement further from the hammer pivot hole means that less force is being exerted on the sear engagement surfaces by the hammer spring. This mechanical advantage means that you can have a lighter trigger pull without reducing the hammer spring power.
The edge at the front of the trigger (where the sear is normally located) is actually the safety/pseudo sear and never comes into play during normal operation. The gold-coloured cuts at the front of the trigger where the normal sear surface are wire EDM cut surfaces. They look different from trigger to trigger due to differences in the base casting. The front pseudosear surfaces are precut before EDM but the wire is run there as a QA step at the same time the top surface is cut. All EDM areas are cut after finishing.
On the SD-3G, which is more of a 'hybrid' than a single stage trigger, the hammer is retained by the trigger hook. As the trigger is pulled backwards, the hook moves forward until it no longer retains the hammer, and the hammer is released. The distance is very short and the pull is very light. On the SSA or Super T, the hammer is retained by the trigger hook. However, before the trigger is able to release the hammer in its forward travel, the front of the disconnector hook touches the top part of the hammer hook, ending the first stage. In order to release the hammer, the trigger is pulled back more, against the spring tension of the disconnector as well. In the single stage trigger, the disconnector does not contact the hammer hook during the rearward travel of the trigger, hence there is no 'second stage'.
Trigger bow - The difference between the SSA and the Super T is the trigger bow. On the USGI trigger with its curved trigger bow, the trigger finger is automatically centered vertically in the curve, about halfway down the trigger. With the Super T, the trigger finger is encouraged to sit below the curve, on the flat part of the bow. With the SD-3G, there's no reference point since the trigger bow is flat. The Super T's profile promotes a more consistent finger position on the bow than the flat bow, and a lower position than the normal curved trigger. Placing the trigger finger lower produces more mechanical leverage (longer moment arm), so the trigger feels lighter the further away from the pivot point the finger is.
The front of the Super T trigger bow has four vertical serrations/grooves and a roughened texture that provide both tactile feedback and purchase when wearing gloves; especially wet ones. The texture is a fine bead blast finish which provides better grip than the standard smooth surface, but isn't uncomfortable at all.
Notes/Observations - In his carbine class, Jeff went over the fundamentals of marksmanship, which included stance, sight picture, what muscles are used to hold the rifle in place, as well as trigger control. Trigger control encompassed not only hand placement on the grip (high), but trigger finger placement on the trigger bow. Not only does placement on the bow affect trigger pull, but whether you center the pad or finger joint on the front of the bow. Jeff came up with the idea for the Super T trigger shape with these factors in mind. He presented it to Bill and the rest is (trigger) history. Basically, the Super T trigger supports or facilitates what Jeff teaches on the range.
The Super T is based off the Geissele SSA, which has an advertised first stage weight of 2.5 lbs and second stage weight of 2.0 lbs, for a total pull weight of 4.5 lbs. I used a Lyman digital trigger pull gauge to measure the pull on the Super T. Note that measurements depend on where the gauge hook is placed on the trigger - the closer to the end it is, the lighter the measurement, so I used my judgement to estimate where my finger would be on the trigger bow and placed the gauge as close to that as possible. I took a number of readings and the frst stage measured around 2 lbs 10-12 oz (approx 2.625 lbs - 2.75 lbs). This is about a quarter pound more than spec'd, but it's within the range I'd expect. The total pull averaged around 4 lbs 10 oz (4.625 lbs), so the second stage ended up being very close to the advertised 2 lbs. For comparison, I measured my SSA trigger and averaged 2.5 lbs for the first stage and slightly less than 2 lbs for the second stage - just a little bit lighter than the Super T.
With the stock USGI trigger, which is a single-stage trigger, there is no 'prep' or 'take-up'. Pressure is increased until the hammer drops. Typically, that trigger pull is gritty and full of creep due to the machined surfaces. With the two-stage Super T, there's a distinct first stage where the trigger can be 'prepped', and let off if the shooter decides not to take the shot, then a precise second stage that Geissele describes as a 'carrot-like' break with very little additional motion of the trigger. The 'carrot-like' break differs from a 'glass rod' break by the elastic feel you get when you bend a carrot that then snaps. A glass rod doesn't bend - it just breaks suddenly when you increase pressure. A carrot has a bit of 'give'.( Note that I'm assuming a fresh carrot is used, not a withered one. With a withered carrot, you'd get a Glock pistol break). In general, a two stage 4.5 lb trigger gives the shooter better control/feel over when the shot is to break than a 4.5 lb single stage trigger.
I noticed this at the range when using the Super T while sighting in rifle optics. After taking up the first stage and hitting the beginning of the second stage 'ramp', subsequent break was predictable and crisp. I've been using the single-stage SD-3G for drills at the range for a couple of years. While it is blazing fast with its short, light pull and short reset, its use is recommended only where rapid target engagement (competition) and quick follow up shots are needed. It's quicker than the Super T for close-up drills like the Bill Drill, but unsuitable for combat or duty use where too light of a trigger pull can become a liability. I also found it harder to break longer range shots (50 yards from standing) as there's no stage - just a drop-off that's harder to predict if you're pulling the trigger more slowly. The Super T has a good balance of lighter-than-stock trigger pull for precise shots, control, safety and reliability.
TACOST card set - At the Jeff Gonzales Combative Carbine 2 class I dropped in on (I wasn't able to attend both days); I was able to get a general feel for Jeff as an instructor. He's articulate, speaks quickly (but clearly), and doesn't mince words. He's very approachable with a good sense of humour and an uninhibited laugh. He's very well organized and efficient, and squeezes out every last minute in the class. This was one class where there was a minimum of standing around B.S.ing or waiting. It was a moderately high round count session because rather than throw a bunch of different drills at the students that they'd only do once, Jeff used repetition of drills so the students could actually practice what they'd just been told and get a better feel and understanding of the drill. In other words, Jeff expects to see a measurable performance improvement in the class from his students; he doesn't just give them a bunch of information to be practiced on their own later. Each round was scored and accounted for, with Jeff keeping track of all scores and giving each student feedback and diagnosing issues on a one-to-one basis. This was what I found interesting; that Jeff was able to observe and diagnose students' issues individually, even though he was the only instructor present. This individual attention is what I felt set Jeff apart from some other classes I've attended.
Now, say you don't have Jeff around, but want to run some of the drills he ran in the class during your own practice sessions. Jeff has come up with a very effective and convenient training aid - the Trident Concepts TACOST Training Card Program. TACOST stands for TAsk, COnditions and STandards, and the training program involves a series of firearms training drills based around a standard 52-card plastic-laminated deck (which can also be used a a normal card deck for card games). Three decks are available: RIFLE 1, SIRT 1 and PISTOL 1.
From the TRICON website:
The majority of the RIFLE 1 sessions are to be peformed at 50 yards and closer. There are a couple of cards for 200 yard and 100 yard drills. All scoring is based on 4" and 8" diameter circles/zones, with some 2" groups included at close range. Scoring is 100 possible points for each drill. Misses are anything out of the designated zones. Each card typically has some of the following information on it:
The shooter can shuffle the deck and draws cards to perform random drills that cover all four performance goals, or pick out a particular set of 13 to narrow the focus. It's left up to the shooter to decide, but takes the guesswork out of deciding what drills to do that day at the range, and makes it fun and challenging for both new or advanced shooters alike. Having a shot timer is necessary for many of the drills. The TACOST set allows the individual shooter or group to set up the training program for the day or range session, in a compact and convenient package. It's a great training tool and helps makes sure that every round you fire is put to good use.
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