Just got a CMC 3.5lb Flat Trigger in today via Granite Ridge Outfitters. My AR is a Adams Arms 7.5'' PDW Evo Pistol, it has a stock trigger from Adams Arms. So i got the old trigger group out of the lower, no issues, just watched some YouTube videos.

So when i went to "drop" the new trigger in, it's not wanting to simply drop in, at least not without force. I pulled the CMC trigger back out and compared it to my stock trigger, visually the CMC trigger itself looks slightly wider than my stock trigger.

So i'm kinda confused on what i should do and what is the issue, is the trigger hole in my lower too small, or is the CMC trigger too wide?

Here are two photos of the issue.

Stock trigger


CMC Trigger


The stock trigger has wiggle room, the CMC trigger wouldn't make it past the opening in the lower.

The stainless housing is not very thick and can/will get bent a little, mine did as well. Either gently bend it a little at a time until it drops in snug or simply push it in, line up the holes and install the pins. BTW the housing has nothing to do with the triggers function, just makes it easier to install in theory..

Edit:

I should have looked at the pictures...  not sure what the issue is there. Either the trigger is out of spec or the lower is. If you can't easily return the trigger assuming it's out of spec then narrowing the trigger blade just a touch would be what I would do.

On my billet lower install I had to thin the CMC trigger a little to get it to drop through the hole.  I did and it was not and has not been an issue at all.

Your trigger slot should measure .312" wide (In Spec.) for your lower...So measure both, your trigger slot and you trigger to find your answer...

Honestly I would take my flat jewelry file and gently relive the lower and move on.

I'd rather lose coating on the trigger than anodizing on the lower myself.. either way will work.

Yup, but I am opposite. I would rather shave a little off the lower and touch up. The lower is cheaper than the trigger

Good point

And the area effected on the lower will never be seen.

Good point, in my case it was just the last 1/4" so I just used the jewelers file on the trigger blade and it's hidden by the lower...  If you have to do the whole trigger, I would relieve the lower instead.

I had the same exact problem with a Quentin Defense billet lower. I opened up the trigger hole rather than thinning the trigger. I had several issues with that lower being out of spec in a few different locations also, so I would assume it is the lower and not the trigger. That same CMC flat bow dropped right in to an Anderson forged milspec lower without any issues just a couple weeks ago which seems to confirm that.

Thanks to everyone for the help!

I just took a metal file and barely took anything off the sides of the opening in the lower, it took a few short passes on the lower and the trigger dropped right in!

Glad you're back in business. Aluma-Black works great for touching up the area you filed, by the way.

Good to know, it's barely noticeable with the trigger dropped in. I'll pick some up, so next time i tear my lower down, i'll touch up the bare spots.

Thanks again to everyone!