SBS 10-8" fix

[Silentweapon338 0]

I see that this topic has been covered extensivly here on the board, but. I got my paper work back last year about this time to SBS a saige a took it down to about an inch before the gas block. I through it in the safe and called it good with all the other projects I had going at the time. I broke my hand in the spring and for some reason decided to pull the gun out and test it, what a stupid time to do so. Guess what it didn't cycle. It was obvious the gun was starving for gas.

 

Last night before reading any of the posts on here I opened the 4 gas holes up 1 drill bt size. It still wasn't enough to make it cycle with 00.

 

I've read the post under this one and basically a whole lot of others they all say send it to Tony or whom ever. Tony seems to be booked up and i can't get him on the phone.

 

If I want to move it to 8" or what ever would make the brake even with a set of Tapco hand guards what do I need to do?

Do I simply move the gas block back 4" from the end of the muzzle cut the piston and gas tube? Do I drill 4 holes back in the new gas block posistion?

 

I have access to all the tools needed ie lathes & mills, but I just need to know where to put the holes and lengths before i go chopping.

Thanks!

[dangerman 0]

There is a similar thread that was just opened today. Check there, I think there are some details as to what you may have to do. BobAsh seemed familiar with the process, but his advice was "ask Tony". Good luck!

[BobAsh 582]

Actually my advise was "take it to Tony".

 

Anyway, here's what I told the other guy with the exact same problem:

 

"Holy crap, you really opened up a can of worms here. You can't just cut the barrel off, it will never cycle. Remember, the entire gas charge is produced as the wad passes through the space between the gas ports and the end of the barrel.

 

You can't just open the gas ports, either. The gas block itself has to be moved 4" closer to the receiver, gas tube and op-rod shortened, new gas holes drilled and the old ones welded up.

 

Moving the gas block is not trivial, since the Saiga barrel tapers larger toward the receiver. This means you will have to chuck the barrel up in a lathe and turn down the barrel so the gas block will go back.

 

Unless you or your best friend is a machinist, I would call Tromix ASAP. Tony can fix your gun." <--Unfortunately this is no longer an option.

Edited September 13, 2007 by BobAsh

[dangerman 0]

Sorry Bob, didn't mean to misquote you.

[Silentweapon338 0]

So basically if I move the gas block back 4" from the action and mimic the current gas hole design I'm in business?

[BobAsh 582]

No worries, DangerMan!

 

The gas block is moved back 4" from is present location. There is some tweaking of the gas hole size, but I don't know what it is.

 

Tony builds the guns, not me. My official role at Tromix is "Design Consultant"....but my contribution is mainly in terms of manufacturing methods. Tony is the brains behind the operation.

 

Good luck. It's a bitch to turn the barrel down once you've cut off the extra length- you may need to get an expanding mandrel to chuck on.

[BobAsh 582]

Although this picture shows the 6" Bodyguard, you can see what's going on.

 

 

[eodinert 1]

If that gun will run with less than an inch of barrel in front of the gas block, the poster's gun should be capable of running, given the proper gas port configuration, correct?

[BobAsh 582]

Tony has made the 6" run reliably on 00. I don't know his methods.

 

The picture is mainly to show what the moved gas block looks like.

[Silentweapon338 0]

I have a tad bit more out in front of the gas block than that. I would be happy to have it run off of 00. Is there anyway you can find out what is done? I can move the gas block and turn it down, but if i can make it work there it would be much easier. Thanks!

You can email me at silentweapon@gmail.com All I want to do is get the gun going!

[BobAsh 582]

While I can appreciate your dillemma, Tony makes his living doing this work and I don't feel comfortable laying out the methods that he spent years developing.

 

If he wants to tell you, that's great; but it wouldn't be ethical for me to do so.

[StealthyBlagga 4]

If that gun will run with less than an inch of barrel in front of the gas block, the poster's gun should be capable of running, given the proper gas port configuration, correct?

 

There are three issues here that interact to determine whether any gas gun will cycle or not:

 

1) Dwell time. This is the time the shot column/wad are in the barrel and holding pressure after they pass the gas ports. Too short and the gun will be finnicky or not cycle at all.

2) The size/number of gas ports. The bigger they are, the more gas gets used to cycle the action, but too big will shave plastic from the wad.

3) The gas pressure at the gas ports. Pressure peaks pretty soon after ignition (say, a few inches down the barrel), then drops off. Gas ports nearer the chamber will encounter higher pressure.

 

I suspect issue 3 is the reason the shorter gas system can compensate for the short dwell time, though I would still expect it to be very sensitive to the ammo and the environmental conditions. Basically, you are corrrect; given big enough gas ports the gun should run as it is - thr problem will be that if the ports are too large the gas system will get fouled by plastic wad shavings very quickly.

Edited September 20, 2007 by StealthyBlagga