What is this noise?

[pwrstrkd]

I dont know how I noticed this but on my m1a when the bolt is held open I can hear something sliding slightly back and forth when I tilt the gun foward then backwards. Does anyone know what is moving back and forth. I dont notice it when the bolt is closed however.

 

[Dane17]

It's the piston. With the bolt closed the op rod is keeping it held forward.

When the piston stops sliding back and forth with the bolt open it's time to clean it.

Sadlak industries makes the 2 specific hand held drills of optimal size for cleaning it.

 

[rehorne]

Yup, that would be the gas piston sliding back and forth. That;s a good thing to hear. Most M-1A owners call that the Tilt Test. As Dane17 sez If it stops sliding back and forth time to clean the gas system