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View Full Version : Yes. You can convert a metric trigger to inch. But it's not easy.


thehandyman
June 25, 2017, 22:31
I am not a professional. This is intended for information and entertainment value only. Doing this wrong can result in a firearm that malfunctions and fires according to its desires and not yours. Doing it right is another 922(r)idiculous part.


Herre you can see the difference behind the triggers, metric, and inch. The Metric trigger has the hole cut in the back of the trigger for the return spring. NOTICE how much excess "meat" the metric trigger has on the back compared to the Inch trigger.

ALSO

Notice how much longer the inch trigger is over all! Follow the INCH trigger up and see all of that meat that is there with the Metric trigger- all that must go! Save an eighth inch (You will see, later!)

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170624_090301801_1.jpg

IMPORTANT: Look at how similar they are in the FRONT. This is your saving grace!

PLEASE NOTE!!! I drilled the pin holes already in this picture! The Metric pin holes are MUCH SMALLER so do not be confused! They look large because I drilled and cored them out to accept the Inch sleeve, to compare them side-by-side! Not hard! Just be careful! Metric trigger pin holes are 3MM or so, Inch pattern holes are 5!!! In this picture they are 5MM, same as the Inch pattern trigger! Be advised!

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170624_090315445_1.jpg

I use an American 5/32" drill bit to core out the trigger pin holes. The Inch trigger uses a 5MM sleeve, the 5/32" is technically 4MM OD, I used a dremel with a diamond bit to core it out to 5MM. THIS IS BY FAR the most important step. If you F this up you will be left with a rifle that is non functional, or worse, dangerous because the sear is held too far back from the hammer. Your 5MM hole needs to be EXACTLY concentric with the existing 3MM holes that are already in the trigger. It's not hard. But it requires your absolute attention and expertise. Do it wrong and you can kill yourself and or other people! It must be exact. As I said.. It's not hard... if you know what you are doing! If not, send it to a machine shop and let them do it! Probably $15, if that!

Once you drill through the mountain holes, the next step is the safety cut in the back. Again, this is so important! The trigger will release the hammer without the safety lever [selector] installed. WITH the safety lever [selector] installed, your trigger is useless! That is because the safety cut is SO HIGH [in the Metric trigger] it hits the safety mechanism [selector] and will not release the hammer.

SIMPLE SOLUTION.

Cut the rear of the Metric trigger exactly as the inch one is. I used an angle grinder. It wasn't hard. An angle grinder is a gross/rough tool, not a precision one! A dremel is better but I have experience with these things. If you are not 100% sure USE A DREMEL. It takes longer but you are much more able to get the angle correct, and the angle is the difference between IT FIRING WITH THE SAFETY ON or not firing with the safety OFF!!!

I mimicked the exact angle, and taper, and yes, it looked weird. But it worked great. Safe position is safe. Fire position is fire! I retained the exact operation of the inch trigger and selector. Not hard!!! Take too much off and safe is no longer safe, it is fire! KEEP THIS IN MIND. Thank you! Touch and go, take a little off and TEST. Use the Inch trigger AS A GUIDE. Doing it blind is insanity! (unless you are Mark at Arizona Response Systems!)

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170624_093952663_1.jpg

Again, we see the safety cut. The Metric trigger has a lot less meat for the safety. But I am involved in some fairly hairy security ops and MY INDEX FINGER is the safety. However it does work! Safe is safe. Fire is fire. Just mimic the angle. If it doesn't work, go back and re- shape. DO NOT TAKE TOO MUCH MATERIAL OFF. Touch and test! You do not want safe to be fire and fire to be fire! People can DIE. This is life AND death, friends! It is a simple, easy step but BE. Careful.

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170624_093956137_1.jpg

What I do not like...

I took too much material off of the underside of the metric trigger housing, exposing the sear spring. It is about 1/8" of material. Like I said, touch and go. Perhaps a slightly ramped contour would have been better, to protect the metric trigger and sear spring. A little silicone may seal that area up, I'm not sure what I will do, if the silicone gets balled up and into the trigger mechanism that can spell death, too.

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170625_192552824.jpg

What I do like:

It is a 922(R) part and you cannot get inch triggers any more. The Apex "L1A1 Inch US Made" triggers are actually Metric (US Made). Which is why I decided to give it a go rather than return it and cry.

The trigger pull got better. But it releases at the end. Once the hammer drops there is no more trigger travel whatsoever. The stock trigger return plunger was even worse. Removing 1/16 from it (Trigger return plunger) solved the problem. I did not need to edit the CAI trigger return spring whatsoever, neither was the spring (Or plunger) from Mark necessary. But the plate with the groove absolutely was. nSee Mark for that, if you want to use the USA Century pistol grip. See Ernst Armory for the L1A1 pistol grip bolt guide (Supply your own washer, your lower might not be as bad as mine!)

I had to cut the trigger return plunger back, 1/16". The trigger almost pushes the trigger return plunger completely back into the plate.

I ordered another trigger return plate from Arizona Response Systems, but did not need the plunger or return spring, I used both from the CAI thumbhole stock.

The Metric fore grip just needed a little shaving on the inner metal portions where they contacted the barrel, behind the strap. (Screw end, very easy, just a little trimming needed)

Metric para carrier worked fine, as did Falcon Arms stainless para springs and guide segment!!!

DSA Para folding stock worked great after I staked the lower for no wiggle room of the protrusion of the para stock, and greased the expansion screw well. I did not enjoy the expansion screw, and wished they would have made a straight threaded bolt for the stock. What I did: I tightened the expansion screw enough to where it was difficult tightening the bolt, I tightened it quite well, then I tightened the expansion screw a LOT, then tightened the bolt as tight as it would go. No problem or stripping. But it is a multi step process!

DSA Para upper (Dust cover!) worked flawlessly.

I have a VERY comfortable wiggle room with 922R parts. Gas piston, even the charging handle was a direct replacement. (DSA) I got the pistol grip bushing and washer, and used he CAI US pistol grip. That gives me enough 922R compliance parts for me to have a foreign mag inserted (Don't you feel safe now??). Forend, pistol grip, rear stock, gas piston, hammer, trigger, sear, charging handle, etc.

Don't let it be said it can't be done, because it can. It cost a couple hundy but it was worth it. Biggest expense was the rear stock. I cut the mounting tab off of the lower as straight as I could, NO PROBLEM. I used a Dremel. No big deal! Just be straight and verify! Verify, verify, verify! You are cutting straight down. Any variance can screw the whole thing up. Again, a machine shop can do this for you if you ware the least bit worried! It's not worth botching it up!

ATN X-Sight II HD 5-20X digital day/night scope with external power pack, and additional batteries for illuminator. Attaches to the folding stock with coiled and angled USB connector perfectly, open or closed. Using a blackhawk stock pack. I can keep the X sight on all day and use as needed. It (pistol grip forend) also holds additional CR123 batteries, as does the forend pistol grip, which will hold a CR12 for the laser (coming, for psychological purposes [showing the enemy, this is where the hole will be if you continue!] as well as aiming) and 2 for the IR illuminator.

Do not ask me what I do, let's just say I need this equipment to work, thanks!

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170625_183138215.jpg

http://img.photobucket.com/albums/v237/wolfmangk/IMG_20170625_183210753_1.jpg

If you want the tactical dog hair you must supply your own dog! (Or Dogs!)

If you want or need help feel free to PM me and I will help you as best I can!

msnyder
June 25, 2017, 22:39
The Dealer Warehouse still has original inch triggers if you don't need it to be US part.

http://www.the-dealer-warehouse.com/cart.php?m=search_results&headerSearch=Y&search=l1a1+trigger

thehandyman
June 25, 2017, 23:03
The Dealer Warehouse still has original inch triggers if you don't need it to be US part.

http://www.the-dealer-warehouse.com/cart.php?m=search_results&headerSearch=Y&search=l1a1+trigger

I have the original inch trigger... The whole point was to keep it a "US" (Century Arms) part.

Thank you for that!

Illurian00
June 26, 2017, 01:13
umm, what do you do ?

msnyder
June 26, 2017, 02:32
I have the original inch trigger... The whole point was to keep it a "US" (Century Arms) part.

Thank you for that!

Yeah, I get you ended up with a US part but when you said, "It is a 922(R) part and you cannot get inch triggers any more." I thought you might have started this journey because you couldn't find any inch triggers.

thehandyman
June 26, 2017, 07:18
umm, what do you do ?

Security at a bubble gum factory. What else would require such hardware? When I say hairy ops what I really mean is when the gum hits the floor it picks up a lot of hair. =D

thehandyman
June 26, 2017, 07:18
Yeah, I get you ended up with a US part but when you said, "It is a 922(R) part and you cannot get inch triggers any more." I thought you might have started this journey because you couldn't find any inch triggers.


No... Just US made inch triggers sadly

Pluribus
June 26, 2017, 16:22
Cool on you for your innovation, just not so sure IMO, that converting a metric to inch now makes it US made unless I missed that it started as a US metric trigger.

thehandyman
June 26, 2017, 16:43
Cool on you for your innovation, just not so sure IMO, that converting a metric to inch now makes it US made unless I missed that it started as a US metric trigger.

Thank you! Yes, the metric trigger started out as a 922r part. It just needed a little modification to work.

Tuhlmann
June 26, 2017, 16:45
I'm more intersted in what happened to your thumb. Do tell!

thehandyman
July 11, 2017, 09:52
I'm more intersted in what happened to your thumb. Do tell!

It's as boring as hitting my thumb with a hammer, one of the things I do is build houses.