Which fix to work on first?

[crusoe 1]

My Saiga 12 has two gas ports, which I have checked to be sure are not plugged with debris.

 

The gas ports will allow a 1 milllimeter paperclip to pass and move within (rattle inside) each port, so they are somewhere between 1-1.5 millimeters.

 

So far I have used only buckshot and shot less than 50 rounds.  On gas setting 1, there are frequent failures to eject.  On gas setting 2, it always ejects and cycles without problem.

 

Here's my question:  Do you think the best first step is to enlarge the gas ports or to work on polishing the bolt/bolt carrier?

 

When I hand cycle, the first resistance is when the protrusion at the back of the gas tube hits the hammer (i.e. the "nubbin" that this forum says NEVER REMOVE MATERIAL FROM).  The next major resistance is when the bottom of the bolt carrier hits the hammer. 

 

My understanding is the it is important that one not reduce the height of the bolt carrier, i.e. the thickness that faces downwards, because it is important for proper trigger reset.  How important is the "ramp angle" that first meets the hammer?  I can see the worn mark where the bolt carrier first meets the hammer.  Is it recommended to "accelerate" the wear and flatten the angle to reduce the force needed to make the hammer ride up (actually downwards) onto the boltcarrier as it moves backwards?

 

A third alternative is to shoot buckshot on gas setting 2 and periodically reduce gas to setting 1 and test for good cycling.  This would in effect be a "breaking in" and allow the parts to wear and reduce friction.

 

 

 

 

[brickfield mfg 86]

I would suggest you get the ports in order first. Get it to what it should have been when it left the factory, then modify it if it is necessary.

[lbsrdi 1,078]

Maybe add a small third port instead of enlarging the existing two.

What is the length of your barrel?

[Billybobf 50]

Only question from me would be if it has a warranty or not?

 

They may fix the issues free of charge, as well as retain your warranty for other issues.

 

You may want to try to carefully look from inside the chamber area and see if its not a three port with a port sitting under the gas block.

[vulcan16 971]

When you remove the gas block , more then likely you will "discover" the third port

Very common for the gas block to cover one of the ports.

Drill the gas block opening with a 5/16 drill bit and screw the D block mod thing.

Open up all three ports to .093 at the correct angle. A toothpick in one of the other ports will help give a visual for the correct angle while drilling.

Reassemble and test.

[gunfun 3,931]

As Jet says, you likely have more ports that are covered which will be exposed.

 

Opinions vary, but I think more small port are better than fewer large ones. .093 tends to let in debris faster. 

Make it a 4 or 5 port. 

Start with 4@0.078" or 5 at .076" angled at 20-30* make sure to leave room to drill up a size if needed.

 

Then smooth the hammer, as shown in the trigger mods link in my signature.

You don't want to reduce how far the hammer moves downward, but you can get the corners off of it, and make sure the bolt face strikes square to the firing pin. As you said, you can smooth the angle of attack on the carrier, but you don't want to change the amount of movement. The idea is to reduce force required to push the hammer past the disconnector, then keep it on the same plane as much as possible. If the carrier has to push the bolt down going back then down again going forward that is bad. It will do a little bit of this, but try to minimize needless motion.

 

Then go over your receiver rails with 3 or 400 grit sand paper until they are smooth and deburred. 

after that, test fire with federal bulk 1 1/8 oz ammo at 1200 FPS. If needed, increase port size in increments of .0002" between tests. 

 

Drill bits can be had at any industrial store for ~$1 each in numbered and lettered sizes in the small increments, so pick up a few steps between .078" and .093 while you are at the store.

 

So to recap my opinion this is your order of operations.

1) get at least 4 ports at a small size

2) profile hammer

3) smooth rails

4) test w/ 3 dram equivalent on setting #2 (and OEM parts other than trigger group)

4.5) If you plan to do a full bolt profile, do it here or along with step 2.

5) increase port size if you don't get 100% reliability at 4.

 

Jumping to step 4 out of order will be a waste of ammo and money.

 

6) show off.

Edited February 2, 2014 by GunFun

[crusoe 1]

Hi guys.  Thanks for all your advice.

 

K.o.t.H:  the barrel is 18"

 

Billybobf:  I don't know if it is under warranty, but I'd rather fix it myself than go through the hassle of sending it somewhere and wondering if I'll ever get it back.  Thanks for the suggestion of looking inside the barrel to see if there is a third port.  I checked and only see the two ports.

 

Jet: Thanks for the specific dimensions of ports and the tip on port angle.

 

Gunfun:  Thanks for the step by step logical approach and the details on materials to use and where to source them

 

I'll let you know how things progress.

[Capt Nemo 882]

Work the action first, then port if more gas is needed.

[crusoe 1]

Thanks for your input Capt Nemo.

 

Based on the low round count, I am planning to work on smoothing the action before working on the ports. 

[brickfield mfg 86]

Work the action first, then port if more gas is needed.

Reverse engineering? Don't you think that correcting the manufacturing errors and get the gun to its design specifications before "improving" it would be a wiser choice? my S12 has all of the ports, they are the correct size, and it functions 100% without any polishing. Not to say that it would not run smoother from polishing - most machines do -  but it works just fine for me as it was designed.

Edited February 4, 2014 by 7.62m43

[Billybobf 50]

On the other hand, less gas= less debris

If he is going to clean an polish a bit, maybe do the first, then only gas enough to operate