Gunsmithing Rim rip AR-15

[GOING FOR 2000]

I have a new upper for my AR-15. It is failing to eject, the extractor is ripping thru the rim. Tried using the bolt and carrier from my old upper, same thing. Tried both bolts and carriers in my old upper works fine.

Chamber looks fine no rough spots.

Any ideas would be appreciated.

 

[Big Dog Steel]

Re: Rim rip AR-15

clean the gas tube and make sure its not binding on the key. Are you running an adjustable gas system? Tell us more about the upper...make, mfg., etc.

 

[deadly0311]

Re: Rim rip AR-15

gas system has something going on. may be bleeding off to much gas and forcing the carrier back to violently or it may be weak brass. What ammo

 

[monteboy84]

Re: Rim rip AR-15

I would have a smith check the chamber, I'm guessing it is out of spec. Not enough taper or something, causing brass to be too hard to eject. I know you said there are no rough spots, I'm just thinking the chamber is dimensionally out of spec. How hard is it to pull the brass after the extractor rips through it?

More details on the upper are definitely needed...

-matt

 

[Scottmilk9]

Re: Rim rip AR-15

..........chamber is probably too tight, might need to hand ream it, make sure its nice and clean.

Do not clean your gas tube!! its self cleaning.

Call us if you need help.

 

[GOING FOR 2000]

Re: Rim rip AR-15

Std XM15e2 set up and 20" barrel.

The extractor rips thru the rim and leaves the case in the chamber. (Meant to say extract in earlier post)

Both function normally as far as ejection and hold open on last.

This problem can occur at any time, can be the first round, fifth, tenth, etc. then occurs every round after that. (pushes out easily with cleaning rod does not even feel stuck) This happens with, factory ammo, reloads (new and used brass Fed, Win, Rem, Mil-surplus.). Nothing odd with fired brass, rings, scars, etc and fired brass will chamber swap in both barrels though snug with a normal bolt drop and extract manually with a hard sharp pull.

Reloads-- Full length SB dies, trimed to length.

Both gas ports are the same size. Gas tube is clean and not binding. The only difference is the one barrel that works properly has a flash hider (irrelevant).

I have also swapped barrels between uppers, gas tubes gas keys, bolt carriers, bolts, replaced extractors on the upper receivers. nothing changes. I figure it has to be something with the chamber.

Both uppers were built with Mil.-spec parts kits, (no markings on upper receivers or barrels), the lower is Bushmaster. Both uppers group well at 100 yds. +/- 1.5" (iron sights)

I built this as something to play with as I am mainly a ELR bolt gun shooter and have very limited knowledge of gas guns. If there is a simple fix good, if not I will forget it, use the upper that works and just replace the other barrel later.

 

[monteboy84]

Re: Rim rip AR-15

It's got to be your chamber, I can't see it being anything else, except for the fact that the casing comes out easily.

The only other thing I see it being is that it is trying to extract the case while under pressure, but I'm at a loss as to what would be causing that.

-matt

 

[Kogapsp]

Re: Rim rip AR-15

New ammo or reloads? If reloads use a small base die to size the the brass.( what small base die do you use? Replace the extractor and spring

kn

 

[GOING FOR 2000]

Re: Rim rip AR-15

Happens with new or reloaded ammo.

RCBS

Already tried replacing exrtactor and spring.

 

[Scottmilk9]

Re: Rim rip AR-15

guy, its one of two things......... chamber a little tight or its your reloads, when i say this its no disrespect or demeaning, it might be a few of your cases might be a tad weaker and making the brass expand more than usual and creating it to stick in the chamber.

What velocities are you running your .223's at?

 

[GOING FOR 2000]

Re: Rim rip AR-15

3000 FPS

Happens with factory loads also.

 

[sobrbiker883]

Re: Rim rip AR-15

I defer to Scott's knowledge on AR's, but the only upper I had that was doing that had too large a gas port and was tossing the timing off. You may want to try an H buffer to slow it down just a hair (bolt may be going back while case hasn't un-expanded from the chamber wall).

 

[i_Adam_i18]

Re: Rim rip AR-15

Pull the upper and drop a round in the tube (a clean tube). If it seats all the way in the chamber without forcing it, it's probably the gas system like sobrbiker said, not the chamber.

 

[deputy1515]

Re: Rim rip AR-15

Just went through this with a new upper. Chamber had not been finish reamed.

 

[sobrbiker883]

Re: Rim rip AR-15

After PM's and reading your duplicate thread in the reloading forum I'd say its chamber related.
Take it to a good AR smith (did I mention Specialized Dynamics?)...

 

[FMJ]

Re: Rim rip AR-15

Kit guns have reject barrels about 50% of the time. The money you save is not worth the aggravation they cause. You can usually tell by looking at the fired brass, they will have multiple rings in the brass from a rough cut chamber.