NM Trigger Installation Problems

[MacRob]

I received my RR EOP upper on Friday. I really like it and look forward to getting into the field soon. The NM trigger that came with it I am not so pleased about.

Because of the horribly long wait for a RR lower I purchased a Double Star lower with standard trigger and A2 stock. This afternoon I spent about two hours trying to install the NM trigger in this lower. It simply won't fit. The instructions that came with the trigger mentioned that the hammer and trigger pins provided are oversized. They sure are. They won't go into the receiver, period! I tried the DS pins with the NM hammer and trigger and could not tell any difference in play so decided to use my old pins. But, the trigger itself will not go in. The rear of the triggr will not slip under the selector switch shaft. I fiddled with it every possible way, including removing the springs to see if I could at least determine if they had anything to do with the problem, to no avail. It looks like the trigger itself is the problem The front of the trigger appears to be too long, where the spring loops over it, to go far enough forward to allow the rear of the trigger to fit under the selector. I think I will give RR a call on Monday. They indicate that they offer two different NM triggers but it looks like one is for large pin lowers which mine isn't. The packaging did not mention anything specific about pin size, except that the pins were "oversize".

I had originally planned to put the upper on a Bushmaster lower, which I told the vendor. He said the trigger would be a drop in on the Bushmaster. However, the trigger opening in the receiver of my Bushmaster appears to be the same size as the one in the Double Star. I think the same foundry makes both receivers any way.

Has anyone here had this problem? If so, how did you fix it? I am a bit hesitant to take the dremel or files to a brand new lower, especially since I am not completely sure that's the problem.

Thanks in advance for any advice you can give.

[abbynormal]

If you have a caliper or a mike, measure the diameter of the pins. If they are .155" they are "Standard" size for use on all AR's except Colts from the last 15 years.

If your pins measure .170" they are for later Colts only

Hope that helps.

I have a RR match trigger group on my Colt and had no problem what so ever installing it.

[1811GNR]

It might make it easier if you remove the selector to install the trigger. It should go in with it in there but maybe not. If you can't get the selector back in afterward you might have an out of spec trigger.

[MacRob]

The instructions call for removing the selector to remove the old trigger, something I discovered was not necessary when I re-installed the original trigger. After writing this I thought of that too. The problem seems to be fitting the rear of the trigger under the selector shaft so, if I leave installing the selector as the last part of the process, maybe it will go in.

Thanks for the suggestions. I will give it a try and let you know.

[highbrow]

I just installed a RRA NM 2 stage trigger in my Bushmaster lower. It would not fit under the selector shaft. Took the selector shaft out, installed the trigger group, replaced the shaft, and all is well. A huge improvement over the stock trigger. And the "oversized pins" are exactly the same as the Bushmaster pins.

[MacRob]

It's done! I simply left the selector out until I had the hammer in. Worked like a charm. RR needs to amend their instructions to read, "if unable to install trigger with selector in place, remove and re-install the selector after installing the trigger." All the safety and function checks went fine. Next up is to mount the scope and get to the range.

By the way, the pins that came with the trigger miked out to .1555". The pins that came in the lower miked to .1535". Two thousands of an inch are not enough to worry about and the larger pins simply were not going into the receiver.

Thanks again for the assistance. This is a great place.

[ravenbkp]

Have installed RR "match" triggers on an LMT and a CMMG pins were definitely larger/tighter on both but doable with moderate force. (lyman tapper), now have a few hundred rounds on both no problems so far.

[MacRob]

I saved the pins supplied with the NM trigger but decided not to try to force them into the receiver. I think LMT makes the Double Star receivers as well as those for CMMG which explains the tiny difference in pin size, alhough I don't quite understand why they want to use the smaller pins instead of what appears to be a standard size. No problem though, unless I lose one, which would mean having to tap in the oversized pins.

Thanks for the information.