9mm ar out of battery/ barrel damage

[garyz]

recently got an ar 9mm using a sylvan Glock mag adapter.
first 100 rounds went w/o a hitch, took it out next day, got an out of battery round.
blew the bottom of the round off the shell and lodged the shell body in the barrel. was able to get it out, by screwing a bolt into the barrel.
into the shell, and then putting a cleaning rod down the barrel from the muzzle end and giving it a whack. got the shell casing out.
i looked into the barrel, and it does not look like there is any damage, but when i took it out today, after full cleaning and lube, lots of oil, could not get
through 5 rounds without an issue, failure to eject feed, shell casing caught in the bolt trying to eject. jam after jam
i looked in the barrel, put a flashlight in end, i didn't see any obvious damage, but what do i know.
anyway, i can check the barrel for damage that i can't see w/ my eyes, or other thoughts on what the issue may be.
ammo was aluminum cased federal and Sellier & belliot brass (sp)

thanks
gary

 

[greencobra]

bother to check headspace?

 

[Uzi2]

recently got an ar 9mm using a sylvan Glock mag adapter.
first 100 rounds went w/o a hitch, took it out next day, got an out of battery round.
blew the bottom of the round off the shell and lodged the shell body in the barrel. was able to get it out, by screwing a bolt into the barrel.
into the shell, and then putting a cleaning rod down the barrel from the muzzle end and giving it a whack. got the shell casing out.
i looked into the barrel, and it does not look like there is any damage, but when i took it out today, after full cleaning and lube, lots of oil, could not get
through 5 rounds without an issue, failure to eject feed, shell casing caught in the bolt trying to eject. jam after jam
i looked in the barrel, put a flashlight in end, i didn't see any obvious damage, but what do i know.
anyway, i can check the barrel for damage that i can't see w/ my eyes, or other thoughts on what the issue may be.
ammo was aluminum cased federal and Sellier & belliot brass (sp)

thanks
gary

There's your answer.

 

[garyz]

I did not check headspace bought the upper complete. Kind of figured the aluminum case ammo may be the cause. Anything I can do to check the barrel to see if it’s junk. Blew the mag right out of the gun when it happened. Or should I just buy a new barrel

 

[240Geezer]

Doubt it's the barrel. I've had similar blowouts with brass cased ammo. Yes they blew out the magazine. May be that Sylvan adapter as I could never get it to run reliably. The lockup point seem to high and the bolt drags on the cases. I tried using a spacer between the magwell and the adapter but then it was too low. I just gave up and bought a dedicated 9mm lower.
All that said I built the uppers ( yes two) from dedicated uppers and 8" barrels and feeding was still iffy so I radiused the breach entry and that fixed it.
I first tried Endomags but plastic rubber feed lips just ain't a thing so another epic fail.
Hey if you're not trying new things then you're just one of the herd.

 

[garyz]

Very little mechanical knowledge. What does radius the breech mean and how would I do that
No actual feed ramp on 9mm barrel Would I polish the face of the barrel and if so what would I use
Thanks for the info

 

[garyz]

i polished the barrel face, system cycles dummy rounds w/ no problems.
was told it could be a light buffer also, any suggestions for a heavy buffer,
not looking to spend a fortune for it
tx

 

[50wt]

What weight is a stock 9mm buffer ?

 

[wcorey]

5.5 oz seems to be the standard for ar9's but it can also depend on bolt weight as well as spring rate. Some claim the 8 or 9 oz work better but fail to mention the other factors so who knows. If using a common 3 oz buffer I'm sure that can cause issues, again depending on the other factors.
The standard length 5.5's are typically under 20 bucks and occasionally under ten when on sale. Because the stroke is so short with pistol calibers, the buffer can be longer, so (expensive) tungsten weights are avoidable, making the real heavies relatively cheaper than the ones typically used for 308 type builds but of course still more than standard length ones.

 

[garyz]

original buffer was 3.2 oz i think, i found one on gunbroker, 8.2 will try that, hopefully
fixes the issues

 

[wcorey]

Looking back at my notes, it seems the 'sweet spot' is typically a couple oz either side of 20, combined weight of bolt and buffer.
Bolts usually come in around 15oz and most have a pinned/removable weight of a couple oz or so.
Carbine length tube with standard .223 spring is in common use but heavier spring/lighter buffer can also work.
Obviously can also be dependent on ammo specs...

 

[garyz]

running factory ammo, put 2 boxes of blazer aluminum case , and them s & b brass
first box of blazer went ok, then 2nd time out, after a full cleaning nothing but issues
ordered the buffer, hopefully will have it before the weekend
going to try my other lower also, see if it is any better

 

[wcorey]

I wouldn’t mess with the 3oz buffer unless you have a heavy (308) spring to go with it. You could also set it up with spacers to increase spring rate, with being mindful of how much it limits bolt travel…