I was fortunate to do a lot of shooting this summer. As often happens when that’s the case, I turn to rimfire to mitigate the ammo cost. After a day out with a Smith & Wesson M&P 15-22 I started thinking it might be fun to do a .22LR build with a binary trigger. After a couple of emails back and forth with Franklin Armory I ordered one of their binary trigger kits and got started.
What’s the Best Base for a Build?
My initial thought was to use my M&P as the base for my build and just have a dedicated .22 binary setup. I Googled around and saw a number of folks who had done just such a build so I reached out to Franklin Armory to see what they said about the compatibility of their triggers and my Smith rifle.
I’m glad I did that because it turns out Franklin doesn’t recommend using their triggers in any polymer lower, even one on a .22LR rifle. Obviously folks are doing it, but I decided to stick to their advice and look for another platform.
I didn’t have another dedicated .22LR build, but the folks at Franklin mentioned that their triggers work fine with a .22 conversion kit in a 5.56 AR. That opened up a lot of possibilities. I ordered a BFSIII AR-C1 trigger kit right away.
My first though was to use a lower I had set aside for a future M-16K build. I paired it up with an H&R brace and the upper off of my Micro-16A2 build from earlier this year. It wasn’t a bad setup at all, but I figured if I was going to use the Micro A2 upper, I may as well use the whole gun, so that’s what I did.
The Binary Micro-16A2
As a quick recap — my Micro-16A2 is an SBR on a Bad Attitude lower, with an entry stock and an A2 upper with a 7.5 inch 5.56 barrel assembly. You can see the full build details in this article.
It’s a neat little package and a bit of a beast shooting 5.56 ammo. You have to watch your hand placement as the front sight base and end cap heat up pretty quickly. There isn’t a lot of handguard space with that pistol-length gas system.
That shouldn’t be an issue using it with a .22 LR conversion kit, though. I swapped out my chopped pistol grip for a full sized A2 grip for this mod.
The CMMG .22 Conversion Kit
As luck would have it, I had picked up a CMMG conversion kit from Brownells earlier in the summer. I had been using it with my other retro builds. It worked well in my full-sized GM M16A1 clone, and Israeli Menusar clone. All you need to do to convert your 5.56 to .22 LR is swap your bolt carrier group, and use the included conversion mags.
Black Dog Machine conversion magazines will work with the CMMG kit as well, and I just ordered some of their 15-round mags since they have the profile of a GI 20-round magazine. I figured they’d look better in the retro guns than the modern style 25-round CMMG mags that came with the kit.
I dropped the CMMG bolt into my Micro-16 and everything function checked fine so it was just a matter of installing the Franklin binary trigger.
The Franklin Arms Binary Trigger
I ordered the BFSIII AR-C1 AR kit with a curved trigger to keep the setup close to a GI trigger since I planned on using it in a retro style build. The kit comes with the Franklin trigger group, an ambidextrous safety, and a replacement recoil spring.
I didn’t need the recoil spring since the .22 conversion kit doesn’t compress the buffer and spring in an AR anyway. All recoil and cycling happens within the space of the BCG itself. The AR buffer and spring just keep the conversion unit in place. They can also be used in an AR without a buffer at all and just an end plate.
Installation of the Franklin binary trigger is pretty straightforward. If you can install a GI mil spec trigger you can install the Franklin. You get two sets of springs with the binary trigger, mil spec and a lighter set. I opted for the mil spec weight since I thought the extra power might be better for reliable ignition of rimfire rounds.
The trigger has a set of spacers that fit on either side of the trigger group that need to be slid into place when you install it. There’s a little more fidgeting doing this than just dropping a GI trigger in, but it’s not hard.
The Franklin trigger assembly comes assembled from the factory with a spacer pin holding it together. You want to leave this pin in place until you drive it out with the trigger pin once the trigger is seated in the lower receiver. There’s a little more juggling of parts than installing a standard trigger. It wasn’t overly complicated, though, and I suspect I’ll be quicker with my next one after seeing how it works.
The last step is to drop the safety in, which is the same as any other AR safety. I will note that Franklin Armory provides a red sticker that goes over your selector markings indicating the binary firing mode. I’ll be honest, I’m not a fan of the big red sticker, but I understand the reasoning.
If someone were to handle the gun who isn’t aware of the binary firing mode it could present a safety issue if they don’t realize it’s going to discharge a second round when they release the trigger. What the sticker may lack in aesthetics it makes up for in ensuring there are no accidents.
The Franklin safety is an ambidextrous unit with a full-size selector on one size, and shorter one on the other. I’d actually like to see a more traditional, single-side trigger for my retro builds, but I suspect I’m in the minority. The provided safety is well made and works as intended.
Micro-16 Goes Brrrrrt
After installation I ran the function checks on my build as per the Franklin Armory instructions. Everything looked good, but I still halfway wondered if I had done it right. The proof would be seen on the range and fortunately I was able to go out the very next day to test it.
I started with CCI Mini Mag ammunition to eliminate any ammo-related issues. I’ve used a lot of that in semi-auto .22’s and have always had good success with it. I loaded up a 25-round mag and chambered my first round. I started on semi-auto, and adjusted my sights to point-of-impact at 25 yards for the .22LR rounds. So far so good. The conversion kit worked, and the gun ran well on semi.
Once I was comfortable that the gun functioned on semi and was sighted in, I moved my selector switch two clicks, from safe to binary. With my first pull and release I was rewarded with two rapid shots, one on the pull and one on the release…exactly how the Franklin Trigger should operate.
I ran a couple magazines through the rifle to get a feel for the trigger. I also confirmed that I could fire one round, hold the trigger back and move the selector to semi auto to keep a second shot from firing. Again, Franklin’s trigger performed exactly as it was supposed to.
I went through about 150 rounds in my first range session. I tried three different types of ammo and got used to the rhythm of the trigger. The CCI ran perfectly as did some 40gr high velocity Winchester ammo I had. I had some older Remington 36gr hollow point loads that gave me some feeding issues. That’s more likely a compatibility problem with the conversion kit than with Franklin’s trigger. A couple of times it seemed like the trigger didn’t reset, but I’m going to lay this on the feed and cycling issues. I didn’t have that problem with the other ammo.
Rimfires can be notoriously picky to begin with and when you’re cycling them as fast as you can with the binary trigger, it likely exacerbates the issue. I have a pretty good mix of .22 ammo and some I have relegated to use in revolvers and bolt action rifles. The Remington went into that pile. Any new ammo I buy, I try to get loads designed to work in semi autos unless it’s something suppressor-specific.
The Poor Man’s SMG
I’m really pleased with the combination of the CMMG conversion kit and the Franklin Arms BFSIII AR-C1 binary trigger. With proper ammo selection, it’s a reliable setup and it’s a ton of fun to shoot. I don’t feel as bad blowing through .22’s as fast as I could, compared to doing that with 5.56. I had no hesitation in wreaking havoc on clay birds I’d set up on the backstop, one mag at a time. The lack of muzzle blast and complete lack of recoil made shooting fun, too.
The binary trigger may not be quite like shooting full auto, but it’s certainly fast and fun. It’s also a lot more affordable. While the triggers normally run $429.99, you can currently get this model on sale for $299.99. The kit I bought is on sale because shortly after I got it Franklin Armory released a new, updated AR-ELITE trigger kit that includes both straight and curved triggers, two enhanced buffer springs, and a lighter hammer and trigger spring. The new kits are the same $429.99 that the old kits ran, even with the extra components.
If you want one of the old single trigger kits at the sale price you probably should grab one soon, because once they’re gone, they’re gone.
While $300 or $400 for a trigger isn’t cheap, it’s still thousands less than it would cost to get into any full auto setup. You also don’t need to worry about a tax stamp, unless you use the trigger in an SBR build like I did.
The Micro-16A2 with the BFSIII AR-C1 trigger may not be a true subgun, but it’s likely as close as I’ll ever come to one. For shooting steel, clay birds, and milk jugs though, my poor man’s SMG works just fine.