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So I recently built an AR pistol, it has a 10.5" barrel with a pistol length gas system. I loaded it up with brand new American Eagle 55 gr and the first shot we fired through it ended with it tearing the rim off the case and leaving it in the chamber. I cleared that and fired a few more rounds and it worked but seems to be tearing the rims up, not enough to leave them in the chamber but enough to make me concerned about its reliability (not to mention I don't want to beat the poop out of my brass, I just got into reloading and would like to get as much life out of my brass as I can).

Anyways I was wondering if any of you all have had similar experiences and if there is anything I can do to mitigate this (beyond getting a longer barrel/gas system). I'm assuming its having such a rough time extracting the cases because its doing so while the chamber pressure is still high. Will a heavier buffer/buffer spring help or do I need to get a adjustable gas block ? Is this something that will just need a "break in period" ? The barrel is new but the other parts (BCG/Buffer/Buffer Spring) are all old stuff that works just fine in a different upper with a 16" barrel.


Any suggestions would be appreciated!
 
You assume correct, its trying to unlock before the brass has relaxed enough to allow it to happen . Next stop broken bolt lugs.
You can go with the adj.block but that comes with tinkering for different rounds power or projectile mass or both.
Its widely believed that finding a happy place with a heavier buffer is a more reliable solution and a better "dooms day" set up. The adj. block has moving parts and is subject to a lot of heat abuse so they will eventually fail.....all of them, eventually.
Sometimes its the only way but most the time it can be done with the buffer spring/buffer weight.
This is common with pistol gas port location/556 combination . The higher power ammo you get the worse it will get.
"Break in " will only get worse as things move easier and the gas port erodes introducing more gas to the system.
 
Pistol length on a 10.5 seems weird. Most are carbine length. Who made the barrel?

It is likely over gassed and the dwell time is F'd. Gas is getting to the bolt too early, and everything said above is true.

An adjustable gas block might assist, as well as a heavier buffer to slow down everything.

Like said above, it's just a wash as this barrel was made wrong in my opinion. Should have been a carbine length at least.

My vote, if possible, get a carbine length 10.5 or 11.5 barrel.
 
It was made by XX-TREME Barrel Company (Yeah that name pretty much screams made by monkeys who couldn't get hired by Century, what can I say it was 45$ and I was on a budget).

Whats worse is I originally was going to get a barrel with a carbine length gas system but during the time it took for me to get paid Primary Arms sold out of them. Then hours after I broke down and ordered this one Primary Arms was back in stock of the good barrel. I considered cancelling the order with the other company but I feel like a real tool when I do that kinda thing so I just took a chance on the pistol length gas system.

I think I'll try and pick up a heavier buffer while I save up for a nice faxon barrel. Do ya'll think a h2 buffer would be sufficient ?
 
It was made by XX-TREME Barrel Company (Yeah that name pretty much screams made by monkeys who couldn't get hired by Century, what can I say it was 45$ and I was on a budget).

Whats worse is I originally was going to get a barrel with a carbine length gas system but during the time it took for me to get paid Primary Arms sold out of them. Then hours after I broke down and ordered this one Primary Arms was back in stock of the good barrel. I considered cancelling the order with the other company but I feel like a real tool when I do that kinda thing so I just took a chance on the pistol length gas system.

I think I'll try and pick up a heavier buffer while I save up for a nice faxon barrel. Do ya'll think a h2 buffer would be sufficient ?
I'd start at H3.
 
It is likely over gassed and the dwell time is F'd. Gas is getting to the bolt too early, and everything said above is true.

An adjustable gas block might assist, as well as a heavier buffer to slow down everything.

Like said above, it's just a wash as this barrel was made wrong in my opinion. Should have been a carbine length at least.

This guy gets it. The AR gas system is a well choreographed dance, and one can't just go around chopping things around...
 
So I went with an Odin Works adjustable heavy buffer for now and am going to be picking up a faxon 11.5" Gunner profile with a mid length gas system whenever I can get the wife to look away from the bank account long enough.

Thanks for all the advice ya'll. I had been pretty sure the pistol length gas system was what was queering the whole system up but wasn't sure I could fix it short term with a buffer change out (I had been wanting to try out one of the adjustable buffers anyways). I'll let ya'll know how it goes.
 
So I went with an Odin Works adjustable heavy buffer for now and am going to be picking up a faxon 11.5" Gunner profile with a mid length gas system whenever I can get the wife to look away from the bank account long enough.

Thanks for all the advice ya'll. I had been pretty sure the pistol length gas system was what was queering the whole system up but wasn't sure I could fix it short term with a buffer change out (I had been wanting to try out one of the adjustable buffers anyways). I'll let ya'll know how it goes.
nice, you will be worlds happier
 
I destroyed a cheap buffer in a 9" 300 blackout once when I first started building and after much research I have used H2 in every barrel under 14.5" since... XXtreem is a cheap barrel for sure, and you get what you pay for.
they probably use the same blank for 762x39 and 300 blackout with only difference between being when they cut the chamber.
The latter absolutely works better with a pistol gas system.
I'd start with an H2,($30 roughly) an investment you'll want to make regardless of barrel manufacturer...the cost of an adjustable block will be a huge chunk towards a better barrel, so I wouldn't throw any money past a buffer to get the XXtreem to work.
 
on the topic of cheap barrels...i spent $67 on my 6.5 grendel barrel from bear creek arsenal and shoot 3/4 moa or better consistantly out to 500 yrds. its an anomaly i guess.
 
on the topic of cheap barrels...i spent $67 on my 6.5 grendel barrel from bear creek arsenal and shoot 3/4 moa or better consistantly out to 500 yrds. its an anomaly i guess.

If you get one that was reamed and rifled with fresh hardware, then it very well could be a great barrel... but then the next one could be an absolute POS.
No telling until you throw it together and send some groups.

OP could absolutely get great results with the XXtreem with nothing more than a buffer swap... although x39 has never been known for accuracy:p

Also OP... they recommend a special fire pin that has a longer protrusion for AR47.. they are like $10.
 
what kind of carrier do you have. M16 will added weight and they made inserts to add more.
this will slow it down a lot, also don't get into buying heavy buffers, make your own.
i use tungsten shot to increase mine
 
there would be a lot more happy pistol gas owners if companies didnt make gas ports oversize all the time . They generally drill to run weak ammo reliable so normal or hot ammo runs way too hard. I've shot a custom drilled pistol location that was a Cadilac but it wouldnt run any steel case or AE......shucked nato rounds well and ran on an standard carbine buffer/standard spring......not sure how a blanket buffer wieght can be recomended ......I have a 10.3 that needs an H3/Wolff XP, 16"midlength 308 on an XH/Tubbs flat wire , a 18" rifle gas 556 on a H/standard spring ....that runs good on a rifle lower as well thats all standard rifle.
 

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