Howdy all. I'm a newbie to ARs and to AR15.com, having recently come over to the dark side from the M1A/M14 world. I'm looking to build an M4-type carbine that will be as durable and reliable as possible. I already have an RRA lower and will soon have an LMT upper assembly. But I'm a bit stumped as to which lower parts kit I should use. Lots of people singing praises to Colt around here, so I'm considering a Colt lower parts kit from SAW (small pin for my RRA lower). Are there any other options?

I'm also considering the Rock River match trigger. Are these anywhere near as durable as Colt? My main consideration is field reliability, not saving a few bucks or having a feather light trigger pull. Thanks.

Field reliability means stay with a standard trigger.  The standard RRA lower parts kit will do quite well for you.

I've had great luck so far with both Colt and RRA lower parts kits. My builds have been a mixture of both, although I have used Colt kits for a few more of them.

My only real (minor) issue with the RRA kits is that sometimes their attention to detail is lacking. Things like having to deburr the selector to make it fit into the receiver, or filing down the bolt catch to fit in it's slot have been (small) issues that I've frequently had to contend with. My most recent RRA parts kit had H/T pins that needed resurfacing to remove the rough spots.

Overall these things aren't a big deal-the actual component quality is good with both kits. When I install a Colt kit I go into it knowing that chances are the parts will drop right in without any fuss whatsoever. When I install a RRA I expect to have to do minor fitting to make everything fit to my (admitedly anal retentive) satisfaction. If fitting isn't required then I consider it a bonus Considering the difference in price this doesn't surprise me-I would be pretty aggravated to pay a premium for Colt parts and then have to screw around to make them fit.

CJan_NH,

I had heard that there was a problem with a batch, but I've never seen it myself.  How many have you seen this with?  I think the only problem I've ever had is with a hammer, and I can't recall if it was RRA.

Any luck with seeing this pic and being able to ID?

I prefer DPMS for one reason: the grip screw.

Some people prefer a hex screw. I prefer a flathead. All the M16's and M4's i've seen have a slotted screw. Some of the parts kits places sell have a hex screw. If you need to get that thing apart in the field, good luck finding a hex screw. I jsut find a slotted screw much easier. And every DPMS kit so far has had slotted screws.

Stick, so far I've used RRA LPKs on eight different lowers. Of the eight, five of them had the nagging little issues I mentioned. My RRA LPKs were purchased in two batches, and come to think of it the "problem" LPKs came from the first batch. My most current RRA LPKs have been good with the exception of a couple of *minor* anodizing issues.

It is quite possible that my earlier LPKs came from the bad batch that you mentioned. That being said, if that's as bad as the problems get I would gladly buy their "bad" parts in a heartbeat. So far I haven't had a problem yet that would discourage me from using them again. The very worst problem I encountered was a defective front pivot pin. It was actually tapered and wouldn't seat fully in the lower. Fortunately I have plenty of spares, so the defective part simply went into the trash and assembly didn't miss a beat.

It should also be noted that my position as a QA technician at Sig makes me a fussy, anal retentive little bastard when it comes to these parts. If they aren't absolutely perfect I take the time to make them perfect. One of my biggest pet peeves on an AR is a selector that turns roughly or has spongy engagement on SAFE or FIRE. I polish the engagement surfaces of the selector until it feels like it's on ball bearings. I also rework the detents and channel for smooth travel and positive engagement. Who knows, maybe in the overall scheme of things I'm just too damned picky. All I know is I haven't built one yet that hasn't been reliable, even when hot

Oh yeah, I forgot to mention that I've never seen a hammer with those marks before

Thanks to everybody for the advice. I think I'll go with Colt for AR project #1, but since it looks like there may very well be an AR project #2 on the way, I might as well buy an RRA kit, too.

This stuff is seriously addictive! There should be a warning label....

I just installed a RRA LPK last night and not one problem at all, no filing no nothing. It went together with my Ameetec lower as if they were custom made for each other. Going by this experience I will only use RRA LPK's. Besides, they're only $54 at Eagle Firearms, you're not going to get a LPK for much less than that no matter off brand you find.

Quoted: I just installed a RRA LPK last night and not one problem at all, no filing no nothing. It went together with my Ameetec lower as if they were custom made for each other. Going by this experience I will only use RRA LPK's. Besides, they're only $54 at Eagle Firearms, you're not going to get a LPK for much less than that no matter off brand you find.

I'm glad to hear that you're happy with your RRA LPK By any chance did you notice if your hammer had any markings on it? I'm specifically wondering if it had a C, M, or F.

Thanks in advance!