Guns with short gas system:Piston wear?

[RRice 34]

I recently took a good look at my S17 after putting a Kross rail and a few other parts on it.Since it was new(3.5 years ago)it has worn a little strange on the gas piston.

 

If I pull the charging handle back and lock the bolt/carrier open and look at it from the top, the piston is off center and is canted towards the ejection port side of the gun.In turn,this is causing the piston to hit the end of the gas tube(not sure what this part is called but is the part that is dovetailed on top for the rear factory sight).It has worn the ejection side of the piston shiny and it appears to be slightly thinner on this side and is wearing the tube part.This part is also loose but nothing too crazy.The gas tube moves about 1/2 MM or so.

 

This gun has done this since new(obviously since the piston is so short)and now has thousands of rounds through it.I noticed the piston wearing after the first time I took it out.

 

Is this typical with guns running this short gas system?Anything I should be looking for.I never plan on selling this gun and with that said I want it to last "forever".

 

Off center;

 

Shiny wear on piston;

 

Slightly rounding the edge of the gas tube;

 

The gun;

[skiboatsp 111]

Tony should be able to resolve this for you without any problem

 

I have seen this on 1 of my many personal 8" SBS s12's I've built

 

There are many tuning technics needed sometimes

 

What I don't see is the hood extension on the gas tube base to help retain the top cover

 

I thought all tromix s17's had this?

Edited January 8, 2010 by saigatechusa

[hobbyshooter 59]

Tony should be able to resolve this for you without any problem

 

I have seen this on 1 of my many personal 8" SBS s12's

 

What I don't see is the hood extension on the gas tube base to help retain the top cover

 

I thought all s17's had this?

I think this is a VERY early Tromix gun.

[mgconnor13 206]

the bolt on every AK rocks a little because the bolt isn't balanced. Never worked on anything with a short piston so a wear pattern like that is new to me. All I can think of is that the way the bolt rocks a little is exacerbated by the shorter piston. I'd contact Tony and see what he has to say about.

[barefootH2O 1]

probably from charging. you pull out and to the right every time you pull the bolt back manually. My 2 cents.

[Matthew Hopkins 1,065]

well I can tell you, you have no gas piston. what you are calling a 'gas piston" is nothing more then the forward part of the bolt carrier. and I can tell you excatly why you are getting that kind of excessive wear on it. a gas piston not only catches the some of the gasand sends the bolt carrier rearward, but it also centers the bolt carrier so that it goes into the rear sight base straight, without it slamming against against the side of the RSB. the way your set up is now, that poor bolt carrier is "freewheeling" it, by slamming against the side of the rear sight block, as it tries to enter the RSB.

 

 

 

 

 

I can tell you it's not going to get any better. only way I can see fixing that is to have part of the carrier in the rear sight base, or add a short gas piston, so that some of it is in the RSB. and not like it is now, just out there into "nowhere land".

Edited January 31, 2010 by Matthew Hopkins

[skiboatsp 111]

well I can tell you, you have no gas piston. what you are calling a 'gas piston" is nothing more then the forward part of the bolt carrier. and I can tell you excatly why you are getting that kind of excessive wear on it. a gas piston not only catches the some of the gasand sends the bolt carrier rearward, but it also centers the bolt carrier so that it goes into the rear sight base straight, without it slamming against against the side of the RSB. the way your set up is now, that poor bolt carrier is "freewheeling" it, by slamming against the side of the rear sight block, as it tries to enter the RSB.

 

 

 

 

 

I can tell you it's not going to get any better. only way I can see fixing that is to have part of the carrier in the rear sight base, or add a short gas piston, so that some of it is in the RSB. and not like it is now, just out there into "nowhere land".

 

Again Tony can fix it.

 

The carrier, top cover, and gas tube mounting block can be tuned. There are probably 500 8" SBS saiga's out there now that work great, this one can be fixed.

 

A quick question, does the top cover have a thin shim welded to the front inside surface?

 

Have you contacted Tony?

Edited February 2, 2010 by saigatechusa