AR PISTOL NOT CYCLING

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

okieshooter777

Sharpshooter
Special Hen
Joined
Sep 20, 2010
Messages
693
Reaction score
856
Location
CHOCTAW
I have a 10.5" ar pistol im having trouble getting to cycle, it is not ejecting or reloading, i can manually eject and it will grab the casing and reload another round fine. something Gas related i assume, but how can i trouble shoot what the deal is and what is happening. ive built a few ar's, but never built or tore into an upper, so not sure where to begin.... upper is pretty new, only maybe a hundred rounds thru it, was operating flawless until now. Originally i thought it was a lower issue, as i bought one of the folders recently and put on this upper, and that is when it first happened. but since i have switched that lower to a different upper and it operates fine. Just something going on with this upper.

tia

-Mike
 

joegrizzy

Sharpshooter
Special Hen Banned
Joined
Mar 19, 2020
Messages
3,821
Reaction score
3,861
Location
nw okc
I have a 10.5" ar pistol im having trouble getting to cycle, it is not ejecting or reloading, i can manually eject and it will grab the casing and reload another round fine. something Gas related i assume, but how can i trouble shoot what the deal is and what is happening. ive built a few ar's, but never built or tore into an upper, so not sure where to begin.... upper is pretty new, only maybe a hundred rounds thru it, was operating flawless until now. Originally i thought it was a lower issue, as i bought one of the folders recently and put on this upper, and that is when it first happened. but since i have switched that lower to a different upper and it operates fine. Just something going on with this upper.

tia

-Mike
sometimes with short barrels, the bullet will exit the barrel *before* enough gas builds up to reliably cycle the action. the gas will take the path of least resistance, and once that bullet exist, that's definitely the easiest path.

so, since it's an ar, you've got a few options: you can tinker with the gas port (potentially drilling it out if the adjustable block doesn't cure the issue), you can tinker with the buffer (altering weights), you can tinker with the BCG by possibly going to a lighter weight material.

if you had a can lying around you could test this theory: with a longer muzzle device that traps (at least some) gas, the firearm may function correctly by allowing enough gas thru the gas port, as the extra time (albeit small) the bullet spends in the can may be enough to get enough gasses necessary for reliable function.
 

Tanis143

Sharpshooter
Supporting Member
Special Hen Supporter
Joined
Jun 5, 2018
Messages
3,062
Reaction score
3,169
Location
Broken Arrow
Some more info is needed. Did you build from a stripped upper or was it purchased as a complete upper. If the former, what barrel and gasblock was used? Have you tried blowing compressed air down the gas tube to see if its obstructed? Which buffer weight are you using? Which bcg?
 

swampratt

Sharpshooter
Supporting Member
Special Hen Supporter
Joined
Nov 3, 2010
Messages
12,720
Reaction score
19,274
Location
yukon ok
never built or tore into an upper, so not sure where to begin.... upper is pretty new, only maybe a hundred rounds thru it, was operating flawless until now. Originally i thought it was a lower issue, as i bought one of the folders recently and put on this upper, and that is when it first happened


Did you put the gun back together as you had it when it was running flawless?

If yes then you may just need to clean up the piston etc and gas tube.
After all it was working fine so I see no need to do any extra mods to make it work.

Your buffer spring may be too stiff with the new lowers.
 

Jason L

Marksman
Special Hen
Joined
Feb 25, 2020
Messages
39
Reaction score
104
Location
Stillwater
You have several things going on here. The upper works on a different lower "flawlessly" and the new folding lower works with a different upper. What is the length of the other upper that is working with the folder?

If the gun was running flawlessly on a different lower and then started this with the folding lower only, I would start with the buffer weight and spring. The buffers for the folding lowers are proprietary, but they do make different weights of them. See if you can find a lighter buffer to run with the short barreled upper (or lighter spring). If you are dead set on running the short upper on the folding lower, then this is where I would start, before you change anything on the upper to make it run. After that would be to pin guage the gas port and see where it is, and maybe enlarge it to make it run on that lower. Only problem then is it may be to overgassed to run on your other lowers which will wear other parts faster.
 

okieshooter777

Sharpshooter
Special Hen
Joined
Sep 20, 2010
Messages
693
Reaction score
856
Location
CHOCTAW
sometimes with short barrels, the bullet will exit the barrel *before* enough gas builds up to reliably cycle the action. the gas will take the path of least resistance, and once that bullet exist, that's definitely the easiest path.

so, since it's an ar, you've got a few options: you can tinker with the gas port (potentially drilling it out if the adjustable block doesn't cure the issue), you can tinker with the buffer (altering weights), you can tinker with the BCG by possibly going to a lighter weight material.

if you had a can lying around you could test this theory: with a longer muzzle device that traps (at least some) gas, the firearm may function correctly by allowing enough gas thru the gas port, as the extra time (albeit small) the bullet spends in the can may be enough to get enough gasses necessary for reliable function.

Some more info is needed. Did you build from a stripped upper or was it purchased as a complete upper. If the former, what barrel and gasblock was used? Have you tried blowing compressed air down the gas tube to see if its obstructed? Which buffer weight are you using? Which bcg?
No was a complete upper, purchased it from bear creek a year or two ago. i have not tried compressed air, but im not exactly sure where i would start.
Did you put the gun back together as you had it when it was running flawless?

If yes then you may just need to clean up the piston etc and gas tube.
After all it was working fine so I see no need to do any extra mods to make it work.

Your buffer spring may be too stiff with the new lowers.
as far as taking the gun apart, i removed the upper from the original lower i built it with, and put it on the 17 design folder lower, and that is when i first noticed the problem so not much of putting together, just pulled pins and installed on different lower. i thought it had to be the 17 design lower causing it, put that 17 design LOWER on another pistol upper i have and it worked fine.
put this BCA upper on another lower and it didnt cycle. So not sure what has happened.
You have several things going on here. The upper works on a different lower "flawlessly" and the new folding lower works with a different upper. What is the length of the other upper that is working with the folder?

If the gun was running flawlessly on a different lower and then started this with the folding lower only, I would start with the buffer weight and spring. The buffers for the folding lowers are proprietary, but they do make different weights of them. See if you can find a lighter buffer to run with the short barreled upper (or lighter spring). If you are dead set on running the short upper on the folding lower, then this is where I would start, before you change anything on the upper to make it run. After that would be to pin guage the gas port and see where it is, and maybe enlarge it to make it run on that lower. Only problem then is it may be to overgassed to run on your other lowers which will wear other parts faster.
THIS upper doesnt work on another lower now, IT DID at one time, see above post.
 

okieshooter777

Sharpshooter
Special Hen
Joined
Sep 20, 2010
Messages
693
Reaction score
856
Location
CHOCTAW
Did you put the gun back together as you had it when it was running flawless?

If yes then you may just need to clean up the piston etc and gas tube.
After all it was working fine so I see no need to do any extra mods to make it work.

Your buffer spring may be too stiff with the new lowers.
that is my thought too no need in mods, could something have failed in the gas block, or likely just got a clog or something along those lines?

I thought originally the buffer spring was too stiff in the new lower, so switched back to other lower and wouldnt cycle either.
 

Latest posts

Top Bottom