M-4 trigger problems

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The Real Hawkeye

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My trigger froze on me. I have an M-4 setup, made from a "pre-ban" Colt receiver and a Bushmaster upper. I also had an after market match trigger assembly installed by the maker of the assembly. Italian name, cannot remember. Done about six years or longer ago. Anyway, it has a sweet trigger. Problem is that the other day I was doing some presentation practice using the EOTECH holographic sighting system and a tactical sling when the trigger froze up. I typically do not do this with a cocked weapon, so I was lightly squeezing the uncocked trigger as soon as the reticle was on center of mass of my mirror image. Been doing this for years and never had a problem, but this time the trigger froze. Usually there is a little take up that I use to simulate a trigger pull. Well, the take up disappeared, and I got concerned, so I cocked the weapon and attempted to dry fire it. Nothing. Frozen. Opened her up and messed around with the trigger group a little, closed her up again and everything was fine, except that there seemed to be some resistance to closing the receiver up that I didn't remember existing before. It required a good bit of pressure to make the upper meet up with the lower enough to push the pin in. These two things concern me. What's going on? I have lost all confidence in this weapon now. Should I have Bushmaster put in one of their current standard trigger groups? Suggestions?
 
It's going to be hard to help without knowing which match trigger you have installed. Personally, I don't see a purpose in a match trigger on a defensive weapon. Just too much to go wrong. If it were mine, I'd put a standard trigger group in.

Jeff
 
Jeff, I think I agree with you. Was struggling along with the rifle when I first got it, and then I saw someone at the range with a similar rifle shooting really tight groups with it, and commented. He let me try his rifle and my groups got to be nearly as small as his, and I asked him about the trigger, and he gave me all the information. I sent it in and they did the install for me. Sounded like a really good idea at the time, but I didn't realize that match triggers were trickier than standard ones. I am seriously thinking about having Bushmaster install their standard trigger group on it at this point. I have lost all confidence in its dependability with the current one in there.
 
I have seen enough match triggers of all kinds fail in training classes that I am convinced they have no place on a defensive weapon. I know that there are a couple members here who have had good luck with them, but I have not seen many that would make it through a three day training class of 1000-1500 rounds.

I've got no problem with them on a weapon that is used for high power or varmit shooting, but it's just something else to go wrong on a duty or personal defense weapon.

Jeff
 
I'm guessing the name you are trying to remember is Milazzo-Krieger. These triggers use a set screw that can vibrate out of place if not loctited down good. They also feature this warning which may or may not be relevant to your problem:

NEVER FIRE OR DRY FIRE THE RIFLE WITH THE ADJUSTING SCREW BACKED OUT LESS THAN 1/2 TURN COUNTER-CLOCKWISE (CCW) FROM THIS "0" POINT.
Click to expand...
 
I've had good luck with the RRA NM trigger. It is a match trigger, but without any of the complexities of set screws or adjustments.

Mike
 
I'm guessing the name you are trying to remember is Milazzo-Krieger. These triggers use a set screw that can vibrate out of place if not loctited down good. They also feature this warning which may or may not be relevant to your problem:
Click to expand...
That sounds like the name, and yes it does have two set screws that appear to be loctited in place. I have not tested to see if they have come loose yet, but might do so. At any rate, I would like a more reliable trigger group, even if it is not a match trigger. So long as the break is crisp, I don't mind a little extra weight. Most Bushmaster triggers that I have tried are good and crisp, even if a bit on the heavy side. Better a little heavy and reliable than delicate in a weapon intended for what this weapon is intended for. I do not compete in Camp Perry type matches, or any but informal local contests, and never seriously. I think of it as serving the same role that the M1 Carbine was designed to serve.

The Rock River Arms match trigger might be worth considering too. How much would the total install cost me, including the hardware?
 
IIRC, you can get a RRA match trigger for under $100 if you shop around. $120 is MSRP, I think.

And "install?" What's that? ;) It's a drop-in part. You can literally do it yourself in under 5 minutes with just a punch to drift out the pins.

Mike
 
Cool! Is the standard Bushmaster trigger group much less expensive, and is it just as easy to install? Is there any chance of doing it wrong and causing problems with function?
 
Well, I managed to do it, so that's probably a "no" when it comes to potential to screw it up. ;)

Really, it is very simple...drift out the pins from the old trigger group, remove old group, place new trigger group in position following the (pretty good) instructions, replace pins. IIRC, the pins have a direction that they're supposed to go in (right to left, I think, and a certain end first), but that's about the height of the complexity.

Will this give you the precision trigger of a Jewell or other high-end adjustables? No. But it will give you a very good, very reliable two-stage trigger that I would have no problem having on a "serious" rifle.

Ask Jeff if he has seen any RRAs fail in training. I'm curious to see if he has. They seem pretty simple and bomb-proof.

Mike
 
Well as popular as they are, I haven't seen that many RRAs in any classes. The State Troopers I know around here all have M16A1s from the 1032 program instead of the Rock River Arms ARs they built for the ISP. So I have to say I don't really know. Let me contact some other instructors and see what the concensus is.

Jeff
 
I went downstairs just now to measure the trigger weights on the two stock ARs that I have in the shop. Just to satisfy my curiosity.

First AR - A Colt AR-15 Carbine model AR6721. Trigger pull averaged 7.4 pounds over three tests, measured with my digital scale.

Second AR - A Stag Arms lower. Trigger pull averaged 9.1 pounds over three tests.

How a 7-to-9 pound gritty trigger can be considered acceptable is beyond me, but some people seem to be happy with them.

All of my AR-15s have 3# JP single-stage triggers. They have survived multi-day three-gun matches and 1200-round training courses. No failures, ever. I've never seen a properly set up JP trigger fail.

- Chris
 
Not sure if this will help or not, but this happened on a buddies Bushy 2 stage NM trigger and it was caused by a primer blowing out of the back of the case and lodging under the trigger. The "tightness" of the trigger group prevented the trigger from moving at all. We got the blown primer out and viola . . it worked like a top.

Good luck!

Regards,
Dave
 
Not sure if this will help or not, but this happened on a buddies Bushy 2 stage NM trigger and it was caused by a primer blowing out of the back of the case and lodging under the trigger.
Click to expand...
I've seen this happen a few times. Most recently (Saturday) with an RRA trigger. Never seen it happen with a single-stage trigger of any kind, although it might be possible...

Probably the best solution is to not blow out primers. :D

- Chris
 
ARs are pretty simple machines. Seems to me that just getting a set of instructions for properly setting up the trigger that's in the AR would be a step in the right direction. Has the trigger group been thoroughly cleaned and properly lubed?
 
Was it possible that this had happened prior, and he just had a primer adrift in the lower, and that it finally worked its way down into the trigger mechanism? Or did you find the case with the blown-out primer?

Mike
 
RRA Match Trigger

Just FYI, but I have to agree with Coronach on the stamina of RRA's 2-stage match trigger under hard use and training.

I attended two tactical rifle courses in the last 3 months. One of my carbines I shot these courses with has the RRA 2-stage trigger group installed. It fired over 800-rds during the first tac rifle course (back in July) and over 1000-rds during the second one. There were no problems whatsoever. Very sturdy during sustained CQB shooting (firing double-taps, triple-taps & 5-rd "hammers"), and it definitely aided accurate precision-shooting on steel silhouettes at 200 & 300-yds.

Also, I talked to two local guys who attended the Pat Rogers Carbine course earlier this summer in Michigan (May or June, can't recall). Their ARs also ran the RRA match triggers and shot the course just fine, each guy firing over 1500rds. They did relate that other rifles had problems, though. One using a JP-something trigger crapped out after a hundred rounds or so.
 
We matched the case with the blown primer. (we'd only shot 10-15 rounds between us and I police all the brass between strings). That day the only thing we shot was XM193 out of the Federal 20 round boxes. Lot 024. (ok, so I'm an anal note taker . . . :) )
 
I have the RRA match trigger and it is possible to install it incorrectly (Takes a bow for hamhandedness) but you will know it immediately as the fire selector will not rotate. I was able to correct the problem quickly though (operator error). It is relatively easy to install and comes with excellent directions. I paid $85 for mine.

However, be aware that the RRA match trigger comes with slightly oversized FCG pins in order to give a good fit. Some people don't care for that. The RRA also uses a lighter hammer and springs, though I haven't had that cause any issues in mine yet.

I've also got a stock Bushmaster trigger that isn't quite as nice as the RRA in crispness but isn't much more in pull weight. If you mix and match the stock triggers, disconnectors, and hammers around you will eventually find a set that fits well together - this assumes you have lots of those parts on hand though and three standard sets of these parts from Bushmaster will cost you as much as an RRA Match Trigger.
 
dmftoy1,
This is the second incident of blown primers with XM193 I've heard of in the past few days. I have shot a lot of XM193 and have never had a blown primer but did have a squibb load with XM193 at Pat Rogers course 3 years ago.

Jeff
 
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