M305 gas piston

[Hornychief]

Hey guys and gals.
Quick one for yah, I recently noticed that my gas cylinder protrudes towards the oprod when the plug is fully tightened.
Is that normal? Oprod is showing wear marks on where it's been hitting the gas cylinder vs it's housing. Also on the bolt side of things, it's not tight in the chamber. I can wiggle it ever so slighty

 

[yomomma]

Piston should be hanging out of the cylinder about 1/4"

The wiggle is what you would call head space.

If your bolt is "in" the chamber yours would be the first one

 

[Hornychief]

Good to know. Wasn't sure if that was gonna be a problem or not

 

[m14medic.ca]

It's called "gas piston protrusion". And as posted above, it is normal and desired.

It serves 2 purposes;

1- it keeps tight contact between the piston and the op-rod. You don't want the piston to "slap" or "smash" into the op-rod when the gas piston starts its movement.

2- it spaces the bolt roller relief in the op-rod so that the bolt roller isn't hard against the steel of the op-rod and saves the roller from repeated stresses (and probable breakage) every time the op-rod slams forward when it is reciprocating.

You can have too much protrusion. I am not entirely sure how much is too much, but I'm sure at some point the op-rod won't drop the bolt fully into battery. I have turned down gas nuts (on the inside edge where it contacts the gas plug) to tighten up an overly large protrusion. There are some m14 gurus south of the border that do this on all their builds to minimize protrusion. The thinking is that it will make the rifle more repeatable and therefore more accurate.

John

 

[Hornychief]

Hey John. Thank you for your input. I was thinking that by having little less protrusion it would make it more consistent by having the bolt in the same place as the shot before and so on. But not something I want to screw around with.