Short stroking. !!!!UPDATE!!!!

Widow maker 223

Active member
I have a home build thats short stroking. Barrel is a .223 wydle Green Mountain 22" stainless H bar, rifle length gas system, .086" gas port. A2 stock with rifle length factory buffer and stock spring. Buffer spring is right length. On the last round in a mag the front of the carrier catches the mag catch, brass ejects at 3:30, sometimes it will eject a round and not pick up another. so I know its short stroking.

I tried a different lower, BCG, mags, still does it. Gas rings are good. Doesnt matter reloads or factory ammo. Gas block is aligned, checked all that with calipers. The gas key was leaking a tiny bit. I put loctite on it and torqued it down, havent shot it yet since doing that. Carrier doesnt drag on gas tube. This is what the barrel looks like under the gas block. Gas block is a Brownells low pro, looks to me like it doesnt seal up worth a crap.
 
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What about the barrel diameter at the gas block? I doubt that's the problem though. I've got a factory RRA upper with a 20" rifle barrel that's leaked from day one but it runs just fine. I'm still learning and gathering parts to build my first upper.
 
with the bolt locking back on an empty mag, but not picking up the next round from time to time its also possible that you're overgassed - and its not picking up the round due to carrier speed being too fast and just overrunning the spring/follower.


verify this that it repeatedly does it by single loading. If it locks back 10 for 10, you're more than likely not under gassed and need to start addressing carrier speed being too high.
 
The bolt isnt locking back all the way on a empty mag. The front of the carrier is catching the mag catch not the bolt. Barrel measures .750". Have not measured the I.D. Of the gas block get.

 
It's possible your gas block tunnel is to small. Not unheard of. I'd try a different block. If no joy make like an oil man and drill baby drill. I'd take it to 0.092.

If you go too much you can always add an adjustable.

Greg
 
The brass marks on the deflector dont mean much.

Trying a different gas block was going to be next and yes drilling the gas port was going to by my last option. I also need to take a good look at the chamber.


If you look at the pic of the gas port closely you can see the size of the hole thats in the gas block in the residue. The blast leaking around it is what doesnt look right, definetly leaking.
 
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All of them form a ring. It's when you see it extend way out on the barrel circumference you have an issue.

I'm pretty sure this will be a drill solution. Chambers don't cause the issues much in my experience.

Greg
 
Originally Posted By: Widow maker 223Im leaning toward drilling to but want to make sure everything else is in check.

The big issue I've seen is the inconsistent power levels of factory ammunition causing unreliability. I'm a firm believer in the adjustable blocks because of that. They also open up a bunch of extra powders that aren't usable with a standard block.

Greg
 
This port is a little on the small side. For a 20" .093 -.096" seems to be the acceptable range.

I know what you are saying with the adjustable gas block. Iv had slower burning powders not have enough juice to cycle reliably.
 
Is the barrel 20" or 22"? If it really is 22", then your gas port size might be correct, since the dwell is slightly longer than a standard 20" rifle barrel. .093" is the correct size for a 20" rifle barrel. That said, I took a quick look at Green Mountain's website, and I didn't see any 22" barrels listed, so make sure you know what you have before you do any drilling.

I think my first move would be to try a different gas block on your barrel. It definitely looks like it's not sealing up very well. It doesn't take much of a leak to cause short-stroking. I would just swap it for a different brand low profile gas block. I've had good luck with YHM and clamp-on would be best, if your barrel isn't dimpled for a set screw. As mentioned before, an adjustable gas block won't gain you anything at all. They're better for things that tend to be over-gassed, like 16" barrels with carbine gas or pistols.
 
green mountain did not start making barrels in just the last day or 2. you would think they surely know what size to drill the gas hole.

doubt that is the problem. though it may fix it in a round about way.
 
Originally Posted By: SlickerThanSnotgreen mountain did not start making barrels in just the last day or 2. you would think they surely know what size to drill the gas hole.

doubt that is the problem. though it may fix it in a round about way.

Oddly enough one size doesn't fit all even on "identical" barrels.. Every barrel maker out there has one that doesn't run on occasion. A fellow could swap to a different lower and see if that works or he can just set it up so it ruins on what he has.

Ritch has a 7.62X39 that ran great from the get go. Mine done at the same time would not and I opened the port. We both run standard buffers and springs. YMMV the same as ours did. Most barrel companies over gas intentionally so they don't have complaints of reliability but that's not always what happens.

Greg
 
Just one other outside to consider...Your action/recoil spring may be too stiff...I had a similar problem on one of my ARs several years back and the solution was to install a lighter weight action spring...Problem solved...
 
before you drill that barrel i would contact the company you bought it from and/or the manufacturer.

soon as you touch a drill bit to it you void any warranty's on the barrel.

make THEM fix it for you, or replace it with a barrel with a proper port size if you do in fact determine thats where your problem is.

if i were in your shoes i'd just send it back, and use the $$ to order another barrel from someone else.
 
What cjclemons said.
I think my first move would be to try a different gas block on your barrel. It definitely looks like it's not sealing up very well. It doesn't take much of a leak to cause short-stroking. I would just swap it for a different brand low profile gas block. I've had good luck with YHM and clamp-on would be best, if your barrel isn't dimpled for a set screw. As mentioned before, an adjustable gas block won't gain you anything at all. They're better for things that tend to be over-gassed, like 16" barrels with carbine gas or pistols.
This is what I did and it fixed my problem. It was leaking real bad around the gas port. I put a Troy clamp on on mine and it fixed the problem. I have clamp on blocks and set screw blocks. From now on I will use the clamp on gas blocks. I just like them better and I don't worry about the screws working loose. Try the cheap things first.
 
Full disclosure - I ripped this pic from someone else's website, but it shows exactly what I'm talking about. The carbon fouling around the gas port should be a nice clean ring about the size of the gas port in your gas block. It shouldn't show any evidence of gas by-passing the whole block. Fix that first, and I'll bet your short-stroking goes away.

ar15jpgasblockinstallationgasport.jpg


If all surfaces are machined correctly, and the gas block is installed securely, that's what it should look like. FWIW, Green Mountain is a reputable barrel maker. Brownell's probably outsourced their gas blocks from the lowest bidder. I'd start there.

My apologies to whoever I stole the pic from!

PS - Clean all that carbon off your barrel before you install a new gas block!
 
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I know what it should look like, the gas leaking was a dead give away when i pulled the gas block. swapped lowers so I know its not the Buffer spring, sealing up the gas key didnt help. Pulled the gas block off it measures .754 top to bottom. .004 too dam big.
 
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