AR Trigger Pin Trouble

[LooseGrouper]

I'm building up a CMMG stripped lower and putting a Rock River NM trigger in, but I'm having trouble with the pins.

I know there are two different sizes, and I ordered the small/standard size pins, but they aren't fitting. The instructions that came with the trigger say that it needs to be .156 pins/holes, but the book I'm using says they are either .170 or .154. I managed to work a brass 5/32 drill bit into the holes to hopefully clear any burrs, but it's a tight fit.

It seems that I could probably get the pins in with a rubber mallet-thumping, but that makes me nervous. I was thinking it might just be the coating on the receiver that is making it such a tight fit.

Anyone have a suggestion?

 

[Bartholomew Roberts]

The Rock River pins are intentionally a thousandth of an inch larger than the standard .154 holes in order to have a tight fit. RRA says that this is because this fit is critical to a good trigger.

This information should be in your trigger installation instructions (or at least it was in mine circa 2004). I went the rubber mallet route and it works just fine - though I do wonder what would ever happen if I put standard trigger pins back into that lower now.