Minor AR Lower issues, Help would be appreciated.

[445cat]

Hi Cal-gunners,

I have been having a couple of minor issues with my AR Lower, maybe you and all your wisdom could help me figure it out. Thanks!

First: My hammer is wearing unevenly to the mag release side. This might be due to hammer and trigger pin placements. I was told to keep the indents to the fire selector side by an online source, but some videos show it being installed with the indents on the mag catch side. Before I take it out and rearrange the entire thing, I wanted to get your opinion.
What side should the Hammer/Trigger pins indents be oriented to?

Second: My bolt does not lock back after the final round of the magazine. I was under the impression it should based on how I've seen others operate. It's not the biggest issue and a quick pull on the CH remedies this but I was wondering what could be causing it?

Is it due to tightness of the magazine catch? Is it the buffer being too heavy? Too light? Could this be a gas issue?

I'm also getting a lot of wear on the rearward inside corner of the Ejection port from ejected rounds, I'm thinking it's a high gas output issue but wanted to check.

Any help would be greatly appreciated. These are not huge operational issues other than the bolt not catching and the rifle operates flawlessly otherwise. A nudge, poke or shove in the right direction would be great. Thanks again!!

[ott1]

Pictures would help show the problems you're having and maybe help others having similar problems.

[SamsDX]

Yes, pictures would definitely help.

There seems to be a lot going on here - what surface of the hammer is wearing prematurely? Is it the face of the hammer? or the entire right side (when looking down on it from the top)?

About the hammer axis pin - I don't think it makes a difference which side it's on, because the center groove lines up with the j-pin inside the hammer and holds it in, while only one of the hammer spring legs are retained within the outside groove. (The opposite hammer spring leg just rests against the pin.

About the bolt not locking back - what happens when you pull the charging handle with the magazine inserted? Does it lock back? Either way, remove the upper with the magazine still inserted. See if the magazine follower is properly pushing up on the bolt catch. I've noticed that with some of the magpul magazines, the bolt catch engagement surface on the follower isn't large enough. Try different magazines, and see if it'll work.

Please show us some pictures of the wear on the ejection port - also, how are the rounds ejecting? (Which direction/angle?)

[rareair]

Second: My bolt does not lock back after the final round of the magazine. I was under the impression it should based on how I've seen others operate. It's not the biggest issue and a quick pull on the CH remedies this but I was wondering what could be causing it?

Is it due to tightness of the magazine catch? Is it the buffer being too heavy? Too light? Could this be a gas issue?

Could be a magazine issue. Check to see if the magazine follower is activating the bolt catch

If the buffer is too heavy or light, you would also encounter cycling issues

[SamsDX]

Speaking of buffers, what length gas system are you using? That would define which buffer you should be using.

[445cat]

that didn't work too well. My apologies for the size of the images, but the wearing should be evident, its the light finish nearest the port on the inside corner of the deflector. and the hammer is just bad. this is all after about 400 rounds.

[adamsreeftank]

Not seeing the pictures.

[445cat]

this should be better. Sorry for wasting anybody's time. I am new, and working through photobucket for the first time. The ejections are straight as an arrow and have healthy distance on them. maybe slightly upward but straight out as usual. Still, no excuse for my fallacy, for those of you that do answer, I very much appreciate the help.

[IMG][/IMG]

[ott1]

On the ejection port issue, have you tried using a different extractor spring, insert or add/remove the extractor spring o-ring?

http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm%20extractor%20spring%20%203pack.htm

[SamsDX]

I'm not sure if any of the wear you're seeing on the upper or the lower are particularly worthy of concern. Keep in mind that during each cycle, the bolt carrier travels rearward to push the hammer back down and to cock it. The front face of the hammer rubs against the bottom surface of the bolt carrier, causing wear on both. After 400 or so rounds that you've put through the gun, that looks about normal to me. It is a little strange that the right hand side is wearing more than the left, but I wouldn't be too worried about that either, if everything else is working flawlessly. I would posit that it could be any one or combination of several reasons: (just hypothesizing, based on how the components interact)
- Bottom surface of bolt carrier is machined slightly unevenly;
- Hammer is machined slightly unevenly (either at the striking surface or at the axis pin/rotational center);
- Bolt carrier rails on the upper receiver are not parallel to each other;
- Upper and lower receivers are not mating in an exactly parallel relationship to each other.

To the extent there is any mismatch, it appears miniscule. You'll have to wear off quite a bit of material in the hammer before it stops striking the firing pin reliably, or it starts to loose structural integrity.

I don't think the wear on the ejection port is particularly notable. Once I get home later tonight I'll compare what you're seeing and the wear on my uppers. It doesn't seem like a gas system issue, because there would be a lot more problems than what you're experiencing.

The bolt catch not working, however, is a functional issue that deserves some attention. Did switching the magazine resolve it?

[General Urko]

The ejection wear mark you have is totally normal. The cases always hit on the way out, thats why they added the big bump on the A-2's so lefties wouldn't take em in the face.. A-1's send em almost straight back leaving that same mark as well. The bolt catch issue may be due to the catch having the wrong spring in it or just binding due to bad fit in its slot.. check that it pivots easily and fully.. oil is your friend, use it on anything that moves. The hammer wear isn't anything to worry about, the finish always wears on them in one pattern or another due to the bolt cocking it on each stroke.

[445cat]

That's great news. I knew that the bolt pushes the hammer back but didn't know if the wear was normal, so that's a sigh of relief.
I asked about the ejection port becasue the wear in the isolated spot was troubling, I thought that the ejected cases were supposed to bounce straight back into the middle of the deflector but I guess every ejection is different. My extractor is very healthy and don't imagine I'll be needing a new one for quite some time.
As for my bolt catch problem, I'm waiting for a new mag in the mail. I'm going to test out the issue up at cow wednesday or sunday and will have a full report then. Thanks for all the help everyone, this community is very gracious.