AR short cycling on reloads

[nosimij]

This is the best place to put this that I could think of.  I did a search but did not see a thread that looked like it is on topic.  If I am duplicate posting sorry.  I am posting here because I am "blaming it on my reloads", but the only thing I can think to do is mechanical.

On my reloads I am noting that my newly built AR is not locking the bolt back on the last round.

I did build my rifle so I am not sure if it is rifle build or reload.  I put what I remember as a carbine spring and buffer.  The lowers kit, did not include stock or buffer is a rock river kit in a rock river lower.

I am using load data directly form the latest Hornaday manual.  55gr Hornaday FMJBTs with Reolader 10X powder in the 2800 FPS column in the manual.  I have not confirmed with a crono.  I am a little longer than the COL, but I do not have the number handy. 

I tried loading more to the center thinking I just needed a little more oomph, but no luck. 

I only had a few factory loads to confirm function on last round and it appeared to.

New Magpol Mags 2 of them both with same issue.

Any suggestions as to where to go?  I am thinking:
     A different buffer 
     Buffer spring
     Pulling the slide stop out and doing some polishing
     
I plan on:
     Finding another rifle to test my reloads in my mags, my reloads in someone else's mags, there upper on my lower with the reloads.
     Reconfirming that it is reloads only that do not function correctly.

Thanks for the guidance.

   

[GASPASSERDELUXE]

You might try increasing your powder charge a little. My volume of the Hornady manual 2012 doesn't list Rl-10 powder for any bullet weight in 223 or 5.56 loadings. If the bolt is not locking back it could be your gas block is misallinged and not getting enough gas.  Have you tried any commercial ammo to see how it works?

[alfsauve]

I'd double check the installation of the bolt-hold-open.   Don't know if it would cause a problem, but make sure you put in the right spring.  Maybe it's too weak or too strong.  Not sure which would be worse.  But for fun you could try going either way. 

Another long shot, but if you have another bolt-hold-open you might compare their dimensions.  I've found some parts just a shade different cause problems.

just trying to provide a slightly different look at the problem.

[PegLeg45]

   
I plan on:
     Finding another rifle to test my reloads in my mags, my reloads in someone else's mags, there upper on my lower with the reloads.
     Reconfirming that it is reloads only that do not function correctly.

Thanks for the guidance.
   

Do this...^^^^^^^^ first.

No need to fiddle with the rifle first (speaking from experience chasing non-existent ghosts in the machine).

If it functions fine and reliably with factory ammo.....then you might need to re-work the loads (unless you really like the load, for accuracy, then you could tune the rifle to the load later).

If the rifle fails with factory ammo, then move to the rifle.

JMHO, FWIW

[MikeBjerum]

First things first:

1.  What do your reloads chronograph at;
2.  Does the bolt lock back on an empty magazine when cycled manually;
3.  Already covered about checking build;
4.  Already covered concerning testing in another rifle.

Good luck!

[Sponsor]

[vincewarde]

The weird thing here is that if your reloads were the problem, I would think it would fail to cycle.  I think the problem is mechanical.  Either magazines or the bolt hold open.  Could the hold open be binding?

[Majer]

I had a problem like this,it turned out the pinhole for the mag hold open latch was a little undersized.A little polishing fixed it.Try the simple stuff first.

[Majer]

Just had another thought,You said you have a carbine spring and buffer,Do you have the rifle or carbine stock on it? there is a difference in them and it could cause the problem as well.

[PegLeg45]

First things first:

1.  What do your reloads chronograph at;
2.  Does the bolt lock back on an empty magazine when cycled manually;
3.  Already covered about checking build;
4.  Already covered concerning testing in another rifle.

Good luck!

This is the first thing I'd actually attempt...(should have mentioned it as well).

Eliminate the mechanism function first.

I still wouldn't tinker or adjust anything until I established if it is the rifle or the round....and you've already outlined a plan to do that. If your loads do not work in your rifle, but do in another, then you're on the right track. Swap uppers and lowers across rifles and that would help determine if it is a gas issue or buffer issue or bolt catch issue.

The weird thing here is that if your reloads were the problem, I would think it would fail to cycle. I think the problem is mechanical.  Either magazines or the bolt hold open.  Could the hold open be binding?

Not necessarily.
I have seen reloads that were just powerful enough to load fire and eject, but did not have enough left in the tank to drive the bolt back far enough to lock open. A minor powder adjustment was all it took on the loads to correct the issue.
I've seen it in rifles and handguns...most often with "softer" target loads.


I agree with you guys that if it is a mechanical issue, then the most likely culprit (after a mag issue) is the bolt hold open...followed by a gas block issue, then buffer. Heck, it could be a combination of several things.

[Magoo541]

I just started reloading for ARs, see my build in Building America's Rifle, I've had a few issues like this as well and I have a few ideas of what is causing it.  First, my reloads used 4064 a slower powder than Benchmark (the burn rate the AR was designed to run and my new powder).  Second, like any auto loader I think there is some break-in required, it took at least 200 to break in my 45 XDM.  My AR is built from a variety of manufacturers and there is bound to be some tolerance stacking which could cause some running slip fits to be on the tight side.

I have run 6 loads with two different bullets and I have 6 more loads with 2 more bulllets I need to run before I load the bullets I have (tight month, the wife says no more trips to the reloading supply store until next month  but I have my change stash  )