ar-15 not cycling
- Thread starter davsco
- Start date
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davsco
Ultimate Member
super appreciate the offer! they're cheap enough and i have one on order.
maybe that will be the key. other than the actual stripped upper, barrel, tube and block, everything else i'm using is off a 16" rifle that has worked perfectly.
357Max
Active Member
Davsco
What is the barrel chambered for .223, .223 Wilde, or .556?
Did you check head space? What is it?
Even though PMC Bronze is .223 it seems like it might be a high chamber pressure problem.
With reduced gas it ejects barely, but full gas = no ejection. Could be case is still expanded under pressure keeping it locked in when hit with full gas/quickest bolt reaction.
What did the cases look like? i.e. swiped, extractor marks on rim, primer condition?
I would not try any .556 in it till you get this gauged!
davsco
Ultimate Member
barrel is wylde. i did not check head space. cases look fine to me. there were no issues at all manually ejecting the spent shells and loading rounds out of the mag. and when shooting it, was pretty clear the bolt wasn't going all the way back. and when they did eject, it was pretty limp, just a foot or two from the rifle.
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danb
dont be a dumbass
I dont think that there is any downside to double checking with a headspace gauge. Worst case, you rule it out.
randomuser
Ultimate Member
I had the same issue with a spring before. Was easy to swap, test and figure it out.
clandestine
AR-15 Savant
Brass looks good.
Before you change anything try other ammo. PMC is not great ammo to troubleshoot with.
Before you change anything try other ammo. PMC is not great ammo to troubleshoot with.
davsco
Ultimate Member
so, quick update. got and installed the non-adj gas block. rifle ejected (but i was in close qtrs so not sure how far) but did not load another round.
so i dropped in my jp low mass bcg and put the upper on my jp ctr02 lower. cycled fine for the couple of shots i took. again, it was not cycling with the same bcg and lower that work on another 16" upper.
so, dumb question, but does a 14.5" need a lighter or heavier bolt, buffer and spring vs a 16" or should those not make a difference, given same mid-length gas system?
so i dropped in my jp low mass bcg and put the upper on my jp ctr02 lower. cycled fine for the couple of shots i took. again, it was not cycling with the same bcg and lower that work on another 16" upper.
so, dumb question, but does a 14.5" need a lighter or heavier bolt, buffer and spring vs a 16" or should those not make a difference, given same mid-length gas system?
davsco
Ultimate Member
super appreciate all your input and advice! i need to keep using pmc bronze because i have a bunch of it and this gun needs to work with it.
danb
dont be a dumbass
my 0.02, you should not need a lighter buffer. You should have plenty of gas (but you dont).
At this point i'd have someone look it over. Among other things: headspace and gas port size. Might not be the low-mass bcg itself, might be the actual bolt. But any fix at this point seems to me to involve sending the barrel back, or some mods to the barrel like opening the port. Either way, you want to be sure before you do any of this.
At this point i'd have someone look it over. Among other things: headspace and gas port size. Might not be the low-mass bcg itself, might be the actual bolt. But any fix at this point seems to me to involve sending the barrel back, or some mods to the barrel like opening the port. Either way, you want to be sure before you do any of this.
- Apr 16, 2017
- 172
Hate to keep throwing guesses at you, but I recently had a problem with my adjustable gas block, and it was the mags. It ran flawlessly with pmags and crap with GI mags. I had tested out multiple types of ammo and buffers, and even added an XP extractor spring before I figured out it was the mags.
I get that situation, but I still think it would be a good idea to try something else, just as a diagnostic tool. What if another brand works flawlessly? Bummer for your stockpile, but you could probably rule out magazines and maybe a few other issues, then get to tuning it in to the ammo you need. You would at least know that your rifle isn't "sick" as a whole.
Now, if other brands act exactly the same way...at least you've eliminated one variable...even if it means your rifle is sick
clandestine
AR-15 Savant
The lower you used for the test? Same lower you had problems with?
What I'm trying to pinpoint is did just installing the JP lightweight carrier make it cycle or was there a different buffer and spring used?
What I'm trying to pinpoint is did just installing the JP lightweight carrier make it cycle or was there a different buffer and spring used?
davsco
Ultimate Member
ok, so what barrel port diameter should i have? it looks similar to other ones i've looked at, but i guess fractions of a mm make a diff. it's def smaller than the gas block ports but i believe that's always the case to help minimize alignment issues? fyi i just measured the pin i used to locate the block, and the pin is 1.63mm so the port is just a skosh larger.
and please help out an idiot like me. headspace is between the bolt and the barrel extension/chamber, right? if the bolt isn't fully seating for some reason, i guess gas is blowing back out the chamber vs being forced down the gas tube, so overall less oomph hitting the bolt, is that right?
and please help out an idiot like me. headspace is between the bolt and the barrel extension/chamber, right? if the bolt isn't fully seating for some reason, i guess gas is blowing back out the chamber vs being forced down the gas tube, so overall less oomph hitting the bolt, is that right?
davsco
Ultimate Member
when it fully worked, i did use the jp full lower, and jp lmos bcg. so yeah, i should use the non-jp lower with the jp lmos bcg and see what happens. and then perhaps just the jp actual bolt and everything else non-jp. i just had a brief window to test so just did the one test.
I think we'll get her running good for you tomorrow...I enjoy a challenge 
Have you taken the bolt out of the carrier to check the gas rings? In addition to mag and buffer issues, that got me once. Caused feeding/cycling/ejecting issues. Rotated them so the slots were staggered and lubed a bit and she ran like a champ.
Just another idea on the heap!
clandestine
AR-15 Savant
If your gun requires this then there's something wrong with your AR.
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