AR Feed Issue

[deadshot556]

Recently assemble rifle with feed issues. 18" barrel, fires, cycles, ejects spent cartridge, but wont pick up another round? Feel free to ask any questions needed. Want this thing to work!

 

[Tim McBride]

Will it lock back if you only put in 1 round and fire? How f ar is it flinging brass? Ammo? Gas system length, buffer system and weight?

 

[Elk34]

Yes it might be short stroking

 

[Seif]

Sounds like it might be under gassed but answers to Tim's questions will help confirm.

 

[deadshot556]

Will it lock back if you only put in 1 round and fire? How f ar is it flinging brass? Ammo? Gas system length, buffer system and weight?

Ammo I've been using XM855, flings it about 3-4 feet, gas system is mid length, and the buffer system is the vltor system A5 kit. No it wouldn’t lock back with just one round.

 

[QuietM4]

Either under-gassed or buffer system is too heavy.

1. Get a lighter buffer or buffer spring.
2. Adjustable gas block that might be turned down (if you one installed).
3. Gas block may be mid-aligned.
4. Gas port may be too small.

 

[Tim McBride]

Will it lock back if you only put in 1 round and fire? How f ar is it flinging brass? Ammo? Gas system length, buffer system and weight?

Ammo I've been using XM855, flings it about 3-4 feet, gas system is mid length, and the buffer system is the vltor system A5 kit. No it wouldn’t lock back with just one round.

I'd start at the front and work my way back:
Is the gas block aligned with the gas port? Is the gas block tight?
Is the gas key tight (and staked)?
Are the Gas rings on the bolt good?

Then I'd look at buffer weight, an A5-H2 is a great starting point, and should be correct for your gun.
If you have access to other buffer weights, try out a lighter buffer.
Still won't lock back, I would then measure the gas port and ask the barrel manufacture if that is correct port size for your setup.

Only as a last step would I open the gas port by one # size.

 

[Harrier]

throwing cases 3'-4' is not what I would consider normal for that ammo... more like 6-8' and normally ejecting between 3pm to 4:30pm max

 

[deadshot556]

Thanks for the info gents. Once I can find a place to shoot/test, I will post results. Funny thing is this entire set up is not new. All I did was change receiver sets. Went from a hogan milled receiver and xrail set up, swapped to a KE arms forged set. Same barrel internal parts, etc. worked fine before. Weird I tell you.
Also the brass is ejecting at 3/4 o’clock

 

[Elk34]

Pressurize the barrel and gas tube with air. Spray it with soapy water. Look for bubbles.

 

[Tim McBride]

Thanks for the info gents. Once I can find a place to shoot/test, I will post results. Funny thing is this entire set up is not new. All I did was change receiver sets. Went from a hogan milled receiver and xrail set up, swapped to a KE arms forged set. Same barrel internal parts, etc. worked fine before. Weird I tell you.
Also the brass is ejecting at 3/4 o’clock

I'd double check everything and then look at the parts you did change, namely the upper. I'd look for wear marks indicating the upper to bolt carrier fit is too tight. I'd also check that the buffer tube inside and make sure that the upper is lining up to the lower correctly and not causing a drag issue there.

 

[Elk34]

If u can't figure it out. I would say, take it to a gun Smith.

 

[sonofbp]

we taking bets?
my "money" is on misaligned gas block making it undergassed

 

[effjaybay]

we taking bets?
my "money" is on misaligned gas block making it undergassed

That's where my my $ would be riding.

 

[Harrier]

Also be sure to run it 'wet'... lube the BCG runners good and look for friction point. Also check the gas tube/carrier gas key alignment... sometime you can get the tube in crooked. . other than that, i concur with the others that the gas block/ system need looked at...

 

[GringoLoco]

what the heck, i'll throw in my 2 cents.

i saw a trigger cause just enough "drag" to slow the whole AR down that it would have issues cycling.

you could just try throwing the upper on a different lower to see what happens. it wouldn't prove the trigger group is the problem but if things worked, you'd at least know it has something to do with the lower rather than the gas system. this all assumes you have a spare lower laying around or a friend that has one.

good luck!

 

[Tim McBride]

Times like this remind me I'm glad to have made my own tube for test firing stuff.
Heavy walled pipe about 4" diameter, cut at an angle and welded to a big 1/2" piece of plate. filled with shredded tires(rubber mulch in your home & garden store). The top has a rubber tile attached with a small hole cut out for the barrel. Pretty quiet and has stopped everything I've fired into it.

 

[deadshot556]

Thanks amigos

 

[Elk34]

we taking bets?
my "money" is on misaligned gas block making it undergassed

It's also called short stroking.

 

[delta6]

we taking bets?
my "money" is on misaligned gas block making it undergassed

It's also called short stroking.

Big difference... "Short stroking" is a symptom, not a cause. I think the OP is looking for the cause.