ACR Trouble shooting

Non-phixion

Non-phixion

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Anyone with ACR experience this is for you guys, if you don't have technical knowledge pertaining to the platform or anything constructive to say please don't sully the thread; i'd like to keep this to the point. I finally got out and shot my ACR for the first time recently and it ran flawlessly with the original 16" 5.56mm barrel and 18.5" 5.56mm barrel. I went to try my brand new 10.5" barrel assembly and what an absolute disappointment. It was failure to extract causing double feed time after time again which was incredibly frustrating for the cost of these barrels. This is a bushmaster OEM assembly, it has an U/S regulator which is unsuppressed and suppressed positions. My thoughts are that the U/S regulator is way over gassing the rifle causing it to send the bolt home with the round still held in the extractor. If anyone has a 10.5" barrel please chime in on your experience and please let me know if you have a U/S regulator or a H/L regulator. The H/L Regulator is for high and low pressures to adjust for .223 and 5.56 mm loads respectively. I do not believe this is an issue with the extractor since the rifle extracted flawlessly with the two long barrels.

Thanks in advance guys!
 
I own an ACR (18.5 inch 5.56 barrel), but never had such double feeds. Here's what I would try though....

You can remove the unsuppressed / suppressed valve assembly. Compare the one that works with the one that doesn not. Are they similar (hole size,etc). Try the valve from one into the other? Does that do anything? The regulator valve is not for different ammo....but for suppressed (can on the barrel) vs unsuppressed.

Just my thoughts.

Graveman
 
Did you try running it on "S" for suppressed? That setting employs a smaller gas-hole in the Gas Plug to reduce the amount of gas required to operate the system with a silencer attached (due to suppressor blow-back into the firearm). That might solve the over-gassing if that is indeed your problem. It does seem as though your bolt velocity is not allowing time for the ejector to spin the cartridge casing out of the way, which would indicate over-gassing. I just find it strange as my 10.5" barrel ran 100% right out of the factory box, using the same "U/S" gas plug swapped over from my 18.5" Barrel.
 
Graveman said:
I own an ACR (18.5 inch 5.56 barrel), but never had such double feeds. Here's what I would try though....

You can remove the unsuppressed / suppressed valve assembly. Compare the one that works with the one that doesn not. Are they similar (hole size,etc). Try the valve from one into the other? Does that do anything? The regulator valve is not for different ammo....but for suppressed (can on the barrel) vs unsuppressed.

Just my thoughts.

Graveman
Click to expand...

this is a good start and easy to do

is there excessive wear on the finish of the piston rod?
 
Graveman said:
I own an ACR (18.5 inch 5.56 barrel), but never had such double feeds. Here's what I would try though....

You can remove the unsuppressed / suppressed valve assembly. Compare the one that works with the one that doesn not. Are they similar (hole size,etc). Try the valve from one into the other? Does that do anything? The regulator valve is not for different ammo....but for suppressed (can on the barrel) vs unsuppressed.

Just my thoughts.

Graveman
Click to expand...

All three of my regulators for their respective barrels are all the same U/S regulators. There is a regulator that exists the H/L regulator which is for .223 loads and 5.56mm for guns that are running overgassed.

Bartok5 said:
Did you try running it on "S" for suppressed? That setting employs a smaller gas-hole in the Gas Plug to reduce the amount of gas required to operate the system with a silencer attached (due to suppressor blow-back into the firearm). That might solve the over-gassing if that is indeed your problem. It does seem as though your bolt velocity is not allowing time for the ejector to spin the cartridge casing out of the way, which would indicate over-gassing. I just find it strange as my 10.5" barrel ran 100% right out of the factory box, using the same "U/S" gas plug swapped over from my 18.5" Barrel.
Click to expand...

Putting it on S settting will not cycle the bolt since there is no back pressure from a suppressor to assist moving the bolt. Already tried S just for ####s and giggles to see if it had any gas to spare, but alas its a bolt gun in S mode.

rambones said:
this is a good start and easy to do

is there excessive wear on the finish of the piston rod?
Click to expand...

No wear on the operating rod, no hot spots or areas it feels like its catching in the action that still feels buttery smooth.
 
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