AR upper on a 11.5 barrel

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Garand101

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Guys First I am new to this Forum so please be easy on me.
This is my second AR build but I am having a problem, I have a AR upper with a 11.5 barrel on a Stag arms lower, My problem is rifle will pick up the first round, chamber and fire and pick up the next,however the spent round does not clear the bolt fast enough before the next round come in.... I am at a bit of a loss, I have changed buffers and changed buffer springs but no difference.
Its not a gas problem as the lower and bolt is used in my stag arms upper with no problems.
Any one have any ideas?
Jay
 
Are you saying the round is properly extracted from the chamber but is then caught by the bolt during the ejection cycle? If so, it sounds like the rifle is over-gased and is cycling too quickly or your ejector spring could be weak. What type of BCG do you have, M16, semi-auto, AR15 enhanced, etc., and what type of buffer are you using.
 
A gas problem (too much), which it sounds like, would show from the barrel swap rather than the bolt or the lower.

My Qs:

-Has this barrel ever worked? Is this something new?
-You say you tried different buffers. What weights? Have you tried a H2 buffer? If the barrels gas port is not way out, then a heavier buffer and a stronger extractor spring and or o-ring should likely help.
-If you have a micrometer, measure the gas port size (under the front sight) and get back to us here.

The difference in weight between a semi and full auto carrier is negligible (about .2oz) vs the difference in weights of buffers, ~1.7oz difference between a carbine and a H2.

Out of curiosity, who made the barrel? Is it new? And, what type of ammo have you experienced this with?
 
The Round is ejecting fine its the cycling its to fast, the spent case get caught by the returning bolt, I will measure the gas port tonight after work, but to me it does seem like a gas problem...to much gas.
The Barrel was picked up from a friend and only had mabey 100 rounds put through it with no issues.
Its an Ar upper and AR Barrel.
I have been firing 55 gr ball and reloads with a 55 gr winchester soft point, with IVI brass using Varget and 23.5 grs of power, Which works great in my 20 inch barrel.
 
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Garand101 said:
I have been firing 55 gr ball and reloads with a 55 gr winchester soft point, with IVI brass using Varget and 23.5 grs of power, Which works great in my 20 inch barrel.
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I'm far from an expert but is there any chance that your bolt is not going all the way back? I ask only because you are using less Varget than any AR15 load I've tried in the past. I usually load at 25-25.5 grains of Varget in a 55 grain bullet weight.
 
Toxic ? What length barrel are you firing Varget from ?

Varget is pretty slow burning, as such, it gasses the system pretty hard. It works well in a rifle length system pushing heavier bullets, but would be obnoxious in a Carbine length system.

My best advice so far is to speed up your powder. Varget is an awful choice for an 11.5 anyway, very inefficient.
If you have a high end barrel and are going for accuracy, and insist on using a top shelf powder, try Benchmark.

Otherwise, if it's a tactical style carbine, try 4198 or 3031.
My 11.5" will rock 4198 all day long, and it only takes about 20.5g so you trim a little off your bottom line.

I've done lots and lots of reloading for 11.5" and 16" Carbines, and 20" Rifles.
 
The Varget works great in the 20 inch barrel,This was my first go with reloads for the rifle so just a starting point, I have done another batch of 50 at 25 grs that I will be trying on the weekend just to confirm!.
 
I would say the bolt is going att the way back as its picking up the next round fine, just cant get the spent case out of the wat fast enough, Had no time last night to measure the gas port so on my list of things to do yet.
 
Conte said:
Toxic ? What length barrel are you firing Varget from ?

Varget is pretty slow burning, as such, it gasses the system pretty hard. It works well in a rifle length system pushing heavier bullets, but would be obnoxious in a Carbine length system.

My best advice so far is to speed up your powder. Varget is an awful choice for an 11.5 anyway, very inefficient.
If you have a high end barrel and are going for accuracy, and insist on using a top shelf powder, try Benchmark.

Otherwise, if it's a tactical style carbine, try 4198 or 3031.
My 11.5" will rock 4198 all day long, and it only takes about 20.5g so you trim a little off your bottom line.

I've done lots and lots of reloading for 11.5" and 16" Carbines, and 20" Rifles.
Click to expand...

I used varget reloaded ammunition in my 7.5 barrel ar without any issues for years. bullet weight from 55 gr to 73 gr. Gas port diameter is .092", Stag regular BCG and regular carbine buffer. The gun will keep it in the "A" zone at 100. Just run the gun well lubed.

A quick fix might be a adjustable gas block OR you may be having an ejector/extractor tention problem( black or blue washer?). Try running the gun with a different BCG
 
Yeah, a lot of people like Varget. I admit, I don't get it. On paper it's an aweful choice, and sure enough, a gave it a good serious chance, but wasn't able to get it to do anything I could not get other powders to do better. Whatever works tho' I guess.
 
Conte said:
Toxic ? What length barrel are you firing Varget from ?
Click to expand...
16 inch mid length and 24 inch rifle length. It does shine more with heavier bullets but I use it for 55 grainers too for the simple reason that it's the only power I regularly keep on hand.
 
Garand101 said:
I would say the bolt is going att the way back as its picking up the next round fine, just cant get the spent case out of the wat fast enough, Had no time last night to measure the gas port so on my list of things to do yet.
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The bolt may not be going all the way back and it may still pick up a new round, there is some give here. Typically if this is happening the last round bolt hold open will be unreliable. It may hold open on the last round but drop when you release the mag or jostle the rifle. A sign of an under gassed rifle.

Although, the situation you describe sounds like an over gassed rifle to me. The bolt carrier travels backwards so fast it bounces of the back of the buffer tube and tries to go back into battery before the spent casing is out of the way. If this is occurring there may be marks on your disconnector from the hammer smacking it, do to the speed of the carrier.

Gas problems are typically do to the gas port on the barrel being over sized or under sized, so it would be a barrel issue if that is the case. Gas problems can be remedied by changing the spring and buffer but this isn’t really fixing the actual problem.

Have you tried any factory ammo?
 
Thanks Mirk, Yes I have tryed IVI ball with the same problem, only way it seems to work right is if you cant the rifle to the side ejection port up, it then will clear the bolt. I know its the upper causing the problem as I switched uppers at the range to my standard barrel and it works fine.
 
Garand101 said:
Thanks Mirk, Yes I have tryed IVI ball with the same problem, only way it seems to work right is if you cant the rifle to the side ejection port up, it then will clear the bolt. I know its the upper causing the problem as I switched uppers at the range to my standard barrel and it works fine.
Click to expand...

I had an over gassed rifle once, the brass was eating up the front of the ejection port, the disconnector was smashed from the hammer, and the back of the buffer looked like it was taking a beating. Also, there were heavy extractor marks; the rim was practically being pulled off of the spent casing. It was bad enough that it would almost get the spent casing back into the chamber at times.

Do you see any signs that would indicate it is over gassed or under gassed?
 
PM me your address and I'll send an AEI viton o-ring in the mail, no charge.
Send me $5 and I'll add a Wolf extra power extractor spring to the envelope.
Try that with your current buffer, then (if you can get your hands on one) try a C7A2 buffer and see if it runs better again.
If it does, purchase a H2 buffer.
Let me know. Good luck.
 
Mirk said:
The bolt may not be going all the way back and it may still pick up a new round, there is some give here. Typically if this is happening the last round bolt hold open will be unreliable. It may hold open on the last round but drop when you release the mag or jostle the rifle. A sign of an under gassed rifle.

Although, the situation you describe sounds like an over gassed rifle to me. The bolt carrier travels backwards so fast it bounces of the back of the buffer tube and tries to go back into battery before the spent casing is out of the way. If this is occurring there may be marks on your disconnector from the hammer smacking it, do to the speed of the carrier.

Gas problems are typically do to the gas port on the barrel being over sized or under sized, so it would be a barrel issue if that is the case. Gas problems can be remedied by changing the spring and buffer but this isn’t really fixing the actual problem.
Click to expand...

Just to say agree, and, a remedy may be in order.
 
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