BCG hitting inside of upper

[Itsmemrj]

I spent a little time at the range this morning. Fired off probably 100 rds through my AR. So right now I am cleaning it and inspecting it for any loose, or damaged things and I notice this on the inside of the upper receiver.



It is hard to tell, but it appears that the BCG is somehow catching the receiver and gouging the hell out of it.



Here is my BCG



Any ideas what might be causing this?

[264Grendel]

Get a POF roller cam pin.

[Itsmemrj]

Get a POF roller cam pin.

POF?

[Itsmemrj]

Get a POF roller cam pin.

Never mind, I googled it.

[CRTguns]

OR get rid of the lame piston thingy. Gene Stoner did not design the AR=15 receiver to handle the torque and torsion caused by a mechanical piston. Mr. Stoner was a smart guy. Nobody has invented any new tech that was unknown to him back in his working days.

Or get a gun that was built to run with a piston:
SIG 556
LWRC
ACR
XCR
FAL
FNC
SCAR
any AK variant
HK SL8
HK "G" anything, or clone. (JLD, CAI, Cetme)
M96 (stoner 63 cloned by Robinson... awesome gun, this one)
AR-180
Original bushmaster rifle.

Its total madness to put incorrect aftermarket parts in your AR-15 then wonder why they're causing damage. Stop it.

[Itsmemrj]

OR get rid of the lame piston thingy. Gene Stoner did not design the AR=15 receiver to handle the torque and torsion caused by a mechanical piston. Mr. Stoner was a smart guy. Nobody has invented any new tech that was unknown to him back in his working days.

Or get a gun that was built to run with a piston:
SIG 556
LWRC
ACR
XCR
FAL
FNC
SCAR
any AK variant
HK SL8
HK "G" anything, or clone. (JLD, CAI, Cetme)
M96 (stoner 63 cloned by Robinson... awesome gun, this one)
AR-180
Original bushmaster rifle.

Its total madness to put incorrect aftermarket parts in your AR-15 then wonder why they're causing damage. Stop it.

The upper is a complete Adams Arms upper, its not an aftermarket kit that I installed. I didnt ask what was better DI or Piston.....

[kcstott]

And Stoner was not that smart ..... he was an aircraft engineer..

[ar15barrels]

Any ideas what might be causing this?

This is a side-effect of a gas piston operating system and a loose fit between the carrier and the receiver.

[ar15barrels]

The upper is a complete Adams Arms upper, its not an aftermarket kit that I installed. I didnt ask what was better DI or Piston.....

Adams Arms installed the conversion before they sold it to you.
The issue is the ROUND bore that does not handle the side-loads generated by the gas piston.
Successful gas piston designs all handle the side-loads with flat rails or square receiver internals that slide on flat surfaces.

[Itsmemrj]

Adams Arms installed the conversion before they sold it to you.
The issue is the ROUND bore that does not handle the side-loads generated by the gas piston.
Successful gas piston designs all handle the side-loads with flat rails or square receiver internals that slide on flat surfaces.

Is there a solution? Someone mentioned a different roll cam pin. I've also got a email into adams arms for help as well.

Thanks in advance.

[kcstott]

The way the gas piston system works is that you are not using the bolt as the piston anymore. so has the carrier ttys to move back and unlock the bolt there are now forces at play that were not there in the original design.
The bolt carrier is being forced to rotate counter clock wise slightly as the cam pin is being forced up the ramp of the caming surface.
You are not going to be able to take the twist out of the motion.

[Eddy's Shooting Sports]

Or get a gun that was built to run with a piston:

HK "G" anything, or clone. (JLD, CAI, Cetme)

Last I checked, everything HK "G" operates via a retarded roller lock blowback. Nary a piston to be found....


Just sayin'




Eddy's Shooting Sports
(650)969-GUNS

[FeuerFrei]

Cam pin wear occures on DI rifles too.
It usually goes to a certain point and then stops.
Turning down the gas regulator to the lower setting will help.
Use grease on that area in stead of drowning it in oil du jour.
Proper action spring and buffer weight for the ammo used will also help.
Need to know if it is a carbine, rifle or midlength gas system to determin spring/buffer combo + ammo used.
Yes the roller cam pin will work in there too.

[ar15barrels]

Is there a solution?

Let Adams Arms deal with it.

[ar15barrels]

Cam pin wear occurs on DI rifles too.

Primarily when the proper chamfer is not applied to the cam pin clearance cut.
The wear stops once that clearance is made.