ArizonaShooting.com

Had a hiccup with an AR this weekend.
It eats factory ammo, but doesn't like the reloads.
The reloads run in every other AR they've been tried in, so I'd like to run a finish reamer just to eliminate the possibility.
It's a fresh assembly with a brand new barrel.

Larry I dont understand 100%

so does it chamber a reload? or not chamber a reload.

if it chambers a reload your barrel is fine I would look into the gas port or maybe buffer weight.

if it doesnt chamber a reload and others do chamber your reloads then you need to ream.

Maybe the dies need a little adjusting,and should try using small base sizing die.

Is your barrel marked .223, 5.56, or .223 wylde?

Also as already asked are you using small base dies?

Usual approach is modify the cheapest part first. You seem intent on reversing that. Is the gas block/FSB on straight? Is the gas port the correct diameter/in the right location? Is the buffer tube smooth and without kinks/binds? Does the bolt/barrel combination pass head space checks?

L. Mike

You might want to find a Go/No Go headspace gauge set for what cartridge your rifle is marked on the barrel first, before you start reaming
the existing chamber.

Dogslayer

Wow.
Thanks for all the replies.

Time to answer the questions:

Delw: The reloads have chambered and fired in every other AR/Mini 14 I've tried. that would be 6 or 7 different rifles.
In this particular rifle, the bolt will not go fully into battery. Close, but not 100%. This rifle ran just fine with factory loads.

CR & ynotaz: I have double checked the dies. They are RCBS small base and I use a Lee FCD. We had a second AR on the line and,
also brand new and unfired,and it ate all the reloads just fine. I will double check the chamber marking this evening.

Blasternaz and Dogslayer: Gas block/FSB is fine. Buffer tube looks good as well. As far as the port size, I can only assume (I know)
that it is the proper size because it cycled everything else it was fed. Honestly, I have never checked
port size on any rifle before.
I don't have a headspace guage, although I should. I will correct that.

My decision to look towards the reamer is based on the advice of some guys I was shooting with. A couple of them are far more knowledgeable than I. most of these issues were discussed, and it was mentioned that the rifle may have a tight chamber and that running a reamer through it couldn't hurt. Reason being that if the chamber is correct, the reamer wont cut.

Or you could bring it to Steve (Action Magic). He recently helped me out with an AR and didn't even charge anything.

Couple other questions I didn't see asked:

1. will assume the OP is trimming the brass down to 1.75"?
2. is the OP seeing any chamber marks on the brass indicative of a tight chamber?
3. what is different about the reloads compared to factory? Faster powder perhaps with the same bullet weight? Case in point - one of my NM ARs hated reloads using AA2230. Short stroked every time. Have forgotten now what the powder charge was, was using Sierra 77g MKs. Not good in a rapid fire string. Switched back to H4895 and the problem went away.
4. does the factory ammo also include GI ammo? If yes and no feeding issues then I doubt it is a gas problem; would look at the point to ammo.
5. swap the buffer with a rifle that does run the reloads - if the issue persists and all items above in 1, 2 and 4 pan out then look to an ammo problem.
6. assuming this is a COTS barrel right? What length? Manufacturer? Gas ports are usually correct out of the factory for the barrel length. Dicking with gas ports without checking everything else first is a good way to ruin the barrel but, we all know that.
7. If it is cycling correctly with factory ammo then the FSB is lined up properly and chances are the gas key is also properly staked and no other obstructions. Gas rings likely no issue either.

I don't want to argue with guys that know a lot but I have a friend who builds unlimited competition custom firearms. He tends to go way beyond the possible problems with an AR because he has never built an AR to see how simple they are next to his sled mounted custom caliber same hole at 200yd gun.

Just a caution on your approach to solving the problem. The folks here might be more practical in their approach to a solution.

The problem with using a reamer first is it will cut, even if the chamber is correct. Try the headspace go and no go gauges first. I would try these in a gun that fed and fired the ammo with no issues also to see how tight the chamber is in it. A variance of .004" in a chamber is common so the problem gun could be at 0, while the other could be at .004".

The tools can be rented for 4D or Elk Ridge online.

That was the solution to my AR-15 and a shooting bud's legal M-16A1. The brass' shoulder likely needs just a very slight push. Be very careful if you crimp with something other than a Lee Factory Crimp die.

As a possible temporary fix. Lower your sizing die and jam the shell holder up real hard against the bottom of the die when re-sizing. It might and I emphasize "might" help. Also using say for example using a RCBS sizer and a Lee or other brand brand shell holder or visa versa could be a possible cause.

If you have a RCBS sizing die. Send your die along with three once fired, never previously resized brass cases. If a small base die is the solution, RCBS will send you another sizing die free of charge.

Better back track, thats what RCBS did for me about 5 years ago, hopefully it is still the same policy. Enclosed with the new die I got was a note warning about crimping causing the shoulder to swell. My friend with the M-16 also did the same with a 308 die he used for his M-1A. Got a new small base die from RCBS no charge.

If you're using a Lee die, forget it. Lee will send you a form letter claiming their die is within SAMI specs. Never had a sizing die problem with Hornady. I did have another problem with one of their expander dies and they promptly sent me a replacement.

Before running a reamer through it try wrapping a piece of emory cloth around a chamber brush and polishing with a cordless drill. See if that addresses the problem.

If a finish reamer cuts something out(do not deepen unless it is a shallow chamber) Then cut it out. its not to size. That why its called a finish reamer. I would first blue the chamber to see if there is a grove then hand(no handle on reamer) turn the reamer, then look for blue locations. But that's just me..

Carry on

There is no stop on a reamer, it will cut way past the proper headspacing if you continue to turn it in the chamber.