I just finished my first ground up ar build. All parts are Rock River except a 16'' Daniel Defense barrel and Daniel Defense M4 free float rail. The first couple of rounds I chambered jammed the bolt closed. I had to do the buttstock slam on the ground to get them out. I recleaned and lubed everything, that problem seemed to go away. Tried firing a few rounds and the rifle apears to be short stroking. I tore the gas system down and reassembled everything being careful to line everything up. I checked the gas key, gas rings, aeverything seems fine and should be, all brand new parts. The only thing I have not tried is switching ammo and mag. I was using a good qaulity mag and don't think that is an issue. This is starting to be not so fun.
Gunsmithing New ar15 short stroking
- Thread starter JohnLaw
- Start date
Re: New ar15 short stroking
What ammo are you shooting?
When you say you tore down the gas system and reassembled everythign being careful to line everything up, did you check the gas tube and the position of the gas block in relation to the gas port in your barrel? Gotta ask because it wasn't mentioned.
My suggestion, get some known good factory ammo and run the gun with a few different mags. Try loading one round first and seeing if the bolt locks back after ejecting the round. Now, the bolt catch can catch the carrier instead of the bolt so you need to make sure that its completely locking to the rear.
If it is still short stroking, time to take the gas block off to make sure you have a clear gas port and that the gas tube is correctly aligned with it. I suspect there would be some indication that this was the issue, maybe some signs of gas escaping there.
What ammo are you shooting?
When you say you tore down the gas system and reassembled everythign being careful to line everything up, did you check the gas tube and the position of the gas block in relation to the gas port in your barrel? Gotta ask because it wasn't mentioned.
My suggestion, get some known good factory ammo and run the gun with a few different mags. Try loading one round first and seeing if the bolt locks back after ejecting the round. Now, the bolt catch can catch the carrier instead of the bolt so you need to make sure that its completely locking to the rear.
If it is still short stroking, time to take the gas block off to make sure you have a clear gas port and that the gas tube is correctly aligned with it. I suspect there would be some indication that this was the issue, maybe some signs of gas escaping there.
Re: New ar15 short stroking
I was using ammo (unkown surplus) that worked fine in my last rifle. When I tore down the gas system I checked and it did not appear to be any gas escaping.Judging by the powder burns on the gas port the gas block wasn't exactly centerd, fixed that. Starting to wonder if it is a recoil spring/ buffer issue. Magpul ctr stock, tube, spring and buffer. I have to stop and get some ammo, and I have a couple of Pmags waiting for me when I get to work tonight.
I did try one round and the bolt carrier did not lock back. It gets stuck about half way back like something is binding it open. When I pull out the bolt carrier I don't see any unusual signs of wear/ binding and it seems to be moving freely when intaled.
Wondering if I instaled the hammer spring incorectly and its causing extra tension?
I was using ammo (unkown surplus) that worked fine in my last rifle. When I tore down the gas system I checked and it did not appear to be any gas escaping.Judging by the powder burns on the gas port the gas block wasn't exactly centerd, fixed that. Starting to wonder if it is a recoil spring/ buffer issue. Magpul ctr stock, tube, spring and buffer. I have to stop and get some ammo, and I have a couple of Pmags waiting for me when I get to work tonight.
I did try one round and the bolt carrier did not lock back. It gets stuck about half way back like something is binding it open. When I pull out the bolt carrier I don't see any unusual signs of wear/ binding and it seems to be moving freely when intaled.
Wondering if I instaled the hammer spring incorectly and its causing extra tension?
Re: New ar15 short stroking
Maybee I tweaked the upper receiver when installing the barrel just enough that I can't see it but its causing an issue.
The one plus i like so far, I put a Smith Vortex on, I let one go after dark and that thing is sweet.
Maybee I tweaked the upper receiver when installing the barrel just enough that I can't see it but its causing an issue.
The one plus i like so far, I put a Smith Vortex on, I let one go after dark and that thing is sweet.
Re: New ar15 short stroking
Learned the hard way about two prong barrel nut wrenchs! Pretty much trashed the barrel nut. Ordered a 3 prong wrench!
Learned the hard way about two prong barrel nut wrenchs! Pretty much trashed the barrel nut. Ordered a 3 prong wrench!
Re: New ar15 short stroking
You will need someone with a borescope to check it out. That is the only way to make sure your gas port is getting enough gas to your tube and gun.
You will need someone with a borescope to check it out. That is the only way to make sure your gas port is getting enough gas to your tube and gun.
Re: New ar15 short stroking
I am going to give him a call thanks for answering my next question, this issue has gotten above my pay grade and I'd rather have someone who knows wha they are doing fix it.
I am going to give him a call thanks for answering my next question, this issue has gotten above my pay grade and I'd rather have someone who knows wha they are doing fix it.
Re: New ar15 short stroking
two things.
make certain the gas tube on the bolt carrier is staked
make certain the buffer tube has a way to exhaust the air pressure at the rear...that means the screw holding the stock at the end of the tube got a HOLE in the screw.
two things.
make certain the gas tube on the bolt carrier is staked
make certain the buffer tube has a way to exhaust the air pressure at the rear...that means the screw holding the stock at the end of the tube got a HOLE in the screw.
Re: New ar15 short stroking
Make absolutely sure that your gas tube is properly aligned so that the gas key on the bolt carrier is not dragging on it.
Also, some shooters lube the buffer spring in an attempt to quiet the "sproing" noise. Too much grease on this spring will also cause short-stroking. A little grease goes a long way here.
Make absolutely sure that your gas tube is properly aligned so that the gas key on the bolt carrier is not dragging on it.
Also, some shooters lube the buffer spring in an attempt to quiet the "sproing" noise. Too much grease on this spring will also cause short-stroking. A little grease goes a long way here.
Re: New ar15 short stroking
1- Make sure the bolt carrier group is well lubed, new parts need a few cycles to wear in. Cycle the action by hand a few times to verify that there are no issues with binding. Check that the gas key is tight on the bolt carrier.
2- Shoot the gun with good factory to eliminate the "unknown surplus" ammo variabilty. Many commercial guns have extra large gas ports to run reliably with weak commercial ammo. So just because this ammo worked before, it doesn't mean that it will work in a gun with the "correct" size gas port.
3- Remove the gas block and check the gas port size. You can use drill bits and calipers. Mil spec size is .063" The gas hole in the gas block is a bit larger then gas port, so any carefully eyeballed alignment job will provide full gas flow. You can also check that there is a good gas flow path back to the carrier.
much as I love snipers hide, the best AR info is at http://m4carbine.net
1- Make sure the bolt carrier group is well lubed, new parts need a few cycles to wear in. Cycle the action by hand a few times to verify that there are no issues with binding. Check that the gas key is tight on the bolt carrier.
2- Shoot the gun with good factory to eliminate the "unknown surplus" ammo variabilty. Many commercial guns have extra large gas ports to run reliably with weak commercial ammo. So just because this ammo worked before, it doesn't mean that it will work in a gun with the "correct" size gas port.
3- Remove the gas block and check the gas port size. You can use drill bits and calipers. Mil spec size is .063" The gas hole in the gas block is a bit larger then gas port, so any carefully eyeballed alignment job will provide full gas flow. You can also check that there is a good gas flow path back to the carrier.
much as I love snipers hide, the best AR info is at http://m4carbine.net
Re: New ar15 short stroking
The more I work the action the better it feels. I am still wondering if I got the wrong spring and buffer, I purchased my CTR 3rd party from gunbroker. It apeared new in the box but who knows.
The more I work the action the better it feels. I am still wondering if I got the wrong spring and buffer, I purchased my CTR 3rd party from gunbroker. It apeared new in the box but who knows.
Re: New ar15 short stroking
The more I am reading I am starting to wonder that also. It doesn't seem to be lodging rounds anymore, they never went in hard just wouldn't come out. I checked and double checked the barrel before I bought it. Daniel Defense M4 profile chrome lined 1/7. Brownels was selling them for $169.00. I called Daniel Defense to double check and make sure it was their barrel, they said yes and couldn't believe the price Brownels had them listed for. I thought it was a safe bet to be a quality barrel.
The more I am reading I am starting to wonder that also. It doesn't seem to be lodging rounds anymore, they never went in hard just wouldn't come out. I checked and double checked the barrel before I bought it. Daniel Defense M4 profile chrome lined 1/7. Brownels was selling them for $169.00. I called Daniel Defense to double check and make sure it was their barrel, they said yes and couldn't believe the price Brownels had them listed for. I thought it was a safe bet to be a quality barrel.
Re: New ar15 short stroking
If You have a 2nd known good rifle You can try swapping the upper and lower halves to isolate the problem to the upper or lower.
It sounds like a tight chamber issue to me also though .
Could be a miss drilled , undersized , gas port also . Doesn't happen often but have heard of it more than once .
If the gas tube is not setting into the upper receiver and dragging on the gas key it can cause problems also .
I would think if the buffer tube wasn't lined up properly the bolt wouldn't cycle properly with or with out ammo in it .
Whether You have the wrong length buffer should be easy to tell as the rifle buffer is about an inch longer than the carbine buffer.
The recoil springs are different lengths also and I don't remember the difference of the top of my head .
If You have a 2nd known good rifle You can try swapping the upper and lower halves to isolate the problem to the upper or lower.
It sounds like a tight chamber issue to me also though .
Could be a miss drilled , undersized , gas port also . Doesn't happen often but have heard of it more than once .
If the gas tube is not setting into the upper receiver and dragging on the gas key it can cause problems also .
I would think if the buffer tube wasn't lined up properly the bolt wouldn't cycle properly with or with out ammo in it .
Whether You have the wrong length buffer should be easy to tell as the rifle buffer is about an inch longer than the carbine buffer.
The recoil springs are different lengths also and I don't remember the difference of the top of my head .
Re: New ar15 short stroking
My money is on tight chamber. Buffer/Spring issue wouldn't cause cause round to stick in chamber.
Send the upper to someone who knows their AR stuff, may just need a turn or two deeper with a reamer.
Did you use go/no go guages to check headspace when you assmebled it?
My money is on tight chamber. Buffer/Spring issue wouldn't cause cause round to stick in chamber.
Send the upper to someone who knows their AR stuff, may just need a turn or two deeper with a reamer.
Did you use go/no go guages to check headspace when you assmebled it?
Re: New ar15 short stroking
did you make sure there was a small gap between the gas block shoulder on the barrel and the gas block? Gap should only be about .010 to .015"
did you make sure there was a small gap between the gas block shoulder on the barrel and the gas block? Gap should only be about .010 to .015"
Re: New ar15 short stroking
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Johnlaw</div><div class="ubbcode-body">Learned the hard way about two prong barrel nut wrenchs! Pretty much trashed the barrel nut. Ordered a 3 prong wrench!</div></div>
FYI: The best is a dedicated PRI 5 Lug tool. 21.00 the last one you wi;ll ever need.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Johnlaw</div><div class="ubbcode-body">Learned the hard way about two prong barrel nut wrenchs! Pretty much trashed the barrel nut. Ordered a 3 prong wrench!</div></div>
FYI: The best is a dedicated PRI 5 Lug tool. 21.00 the last one you wi;ll ever need.
Re: New ar15 short stroking
use of rubber tubing app.1/8''dia 2 feet long and compressed air connect to gas tube with needle nose pliers in back of gas tube in the upper ,hit the air on -you should hear air coming out ,if not gas post to gas block is not lined up or a partly lined up.. one or other is happening .
use of rubber tubing app.1/8''dia 2 feet long and compressed air connect to gas tube with needle nose pliers in back of gas tube in the upper ,hit the air on -you should hear air coming out ,if not gas post to gas block is not lined up or a partly lined up.. one or other is happening .
Re: New ar15 short stroking
Update.
Thanks everyone for the info. It was all helpful. I adjusted the barrel nut just enough to make sure the gas tube was properly aligned. I then reset the gas block again. I sprayed down the gas system and chamber with CLP and then used air to blow everything out. I loaded up some different mags with good quality ammo and proceeded to fire. still short stroking. Rechecked gas block. put some more ammo through. Started to feed but not lock open on an empty mag. I checked around the gas block and could see clp/residue coming out between the barrel and block. Fed more ammo. Started to run flawlessly! I think some gas was excaping from the gas block and it eventuly sealed up. It is now even eating the dreaded Wolf ammo! Decided to return the Luepold CQ/T, put on a vortex strikeforce until I can decide / afford either a SB Short dot, or NF nxs 1-4. thanks everbody. Good Luck1
Update.
Thanks everyone for the info. It was all helpful. I adjusted the barrel nut just enough to make sure the gas tube was properly aligned. I then reset the gas block again. I sprayed down the gas system and chamber with CLP and then used air to blow everything out. I loaded up some different mags with good quality ammo and proceeded to fire. still short stroking. Rechecked gas block. put some more ammo through. Started to feed but not lock open on an empty mag. I checked around the gas block and could see clp/residue coming out between the barrel and block. Fed more ammo. Started to run flawlessly! I think some gas was excaping from the gas block and it eventuly sealed up. It is now even eating the dreaded Wolf ammo! Decided to return the Luepold CQ/T, put on a vortex strikeforce until I can decide / afford either a SB Short dot, or NF nxs 1-4. thanks everbody. Good Luck1
Re: New ar15 short stroking
i realy do think the gas block was the culprit. RRA low prow gas block. Anyone else had a similar situation?
i realy do think the gas block was the culprit. RRA low prow gas block. Anyone else had a similar situation?
Re: New ar15 short stroking
I had some residue on my gas tube where it goes into hte upper receiver recently, finally got my hand grips off my AR - so this has been a helpful post - I may go re-examine mine after shooting next time...
Next thing, put a 30 rd mag in and point downrange and fire it as fast as humanly possible....LOL, that'll get some break-in going for you....
I had some residue on my gas tube where it goes into hte upper receiver recently, finally got my hand grips off my AR - so this has been a helpful post - I may go re-examine mine after shooting next time...
Next thing, put a 30 rd mag in and point downrange and fire it as fast as humanly possible....LOL, that'll get some break-in going for you....
Re: New ar15 short stroking
With the gas block on the last DD barrel upper I assembled, the dimple for the gas block setscrew wasn't big enough for the screw tip to grab. I used the drillpress to slightly enlarge the setscrew dimple and then aligned the setscrew hole with the dimple. Put in the setscrews with some Loctite and it was good to go.
-matt
With the gas block on the last DD barrel upper I assembled, the dimple for the gas block setscrew wasn't big enough for the screw tip to grab. I used the drillpress to slightly enlarge the setscrew dimple and then aligned the setscrew hole with the dimple. Put in the setscrews with some Loctite and it was good to go.
-matt
Re: New ar15 short stroking
Every now and then a bur will remain from after the gas hole was drilled. That can also cause the type ofproblem you are listed.
Every now and then a bur will remain from after the gas hole was drilled. That can also cause the type ofproblem you are listed.
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