[sirtirithon]

Just a quick question about my gas lock and gas port alignment. I removed the gas system from my rifle just to do it. I like to know my firearms inside-out plus I wanted to know how to remove everything for shim installation later on. Before removing it my gas lock did not tighten up at 6 o'clock, more like 7 o'clock, and the ports were not aligned perfectly. It shot just fine though. I reinstalled everything and lined the port in the barrel up directly with the gas port on the cylinder and now my gas lock snugs right up at 6 o'clock. I did not remove my FS so I did not flip the gas lock. I obviously did not tap the gas system as far back on the barrel splines and therefore got a slightly snugger fit with the gas lock. But I judged where to leave the gas cylinder by the port alignment. So my question..is it better to have the gas cylinder tapped as far back as possible and have slightly offset gas port alignment and a loose gas lock or leave it like it is? will the gas system move back while shooting and ruin my threads? I would think that the gas lock and gas plug will hold it where its at. I plan on shimming it soon anyways but I figured this was a valid question regardless...I'd like to know.

 

[Ole Silver]

GS Lock Up

My rifle was the same way when I got it and I did the same thing you did. After a range session it was apparent that the GS was still loose. It just needed to be shimmed.

I shimmed mine so that it was hand tight at about 5 o'clock and used the gas lock wrench to tighten to 6 o'clock. The gas port was still alligned. I think I went .018 with the shims to get mine tight. You'll just need to experiment to see what works for your rifle.

It has been tight ever since. An easy process that made a noticeable difference in accuracy & repeatability.

Ole Silver

 

[SmokyBaer]

Sounds like yours has a fit like mine was. I did flip my gas lock but it didn't improve it greatly. The shims made all the difference. Tapped it all in place with a plastic mallet and hand snugged to 5 o'clock. The wrench brought it home to 6.

I used a drill bit the exact sixe of the gas port to make sure not to overlap with the cylinder. The bit still went all the way thru to the barrel after torqing and that's all you can hope for.

One advantage I learned later was the shims increased dwell time by a hair by securing the gas plug out farther. That allows the piston to seat farther out which gives the op rod a shade longer travel before unlocking the bolt. Jury is out on how much accuracy is gained but I've heard it mentioned a LOT. After you torque your shims in and hand thread your gas plug to the piston, make sure you have 5/8 to 3/4 turn left to torque with a wrench.

Please update how your groups change after doing this shim/dwell upgrade. Mine saw instant improvement. Hopefully, yours will too. Above all, Enjoy!!

 

[NoExpert]

SmokyBaer is correct about the improvements. One thing to note though, make sure there is contact between the piston and op rod when it's all assembled and the op rod is forward. You do not want the piston to smack the op rod, this is bad. Also if there is a gap this means that the bolt and roller are stopping the op rod and not the piston which is really bad. Just some things to be aware of.

 

[bd111]

I'd go ahead and shim it or get the gas cylinder and barrel band unitized before next shooting season. What you had originally was probably OK as long as you had gas into the cylinder. What you have now may have loosened the barrel band between the gas cyl and barrel shoulder.

 

[FPeel]

After you torque your shims in and hand thread your gas plug to the piston, make sure you have 5/8 to 3/4 turn left to torque with a wrench.

3/4 of a turn on the plug with a wrench? Wouldn't that be kind of tight?

 

[Ole Silver]

What Smokeybaer means is that you hand tighten the gas plug until it just makes contact with the piston. Using a wrench then for snugging it up good it should take about 5/8ths to 3/4quarters of a turn.

My gas system snugs up just like Smokey said.

Ole Silver

 

[sirtirithon]

Shimmed the gas cylinder tonight!

Didn't want to start a new thread for this but wanted to update and ask a couple more questions on this process...sorry if I'm long winded...

I received my shim kit yesterday and got around to installing them tonight. I ended up using the largest shim (not sure which size, Fulton Armory didn't specify sizes, but looked to be .010) to achieve what I believe is the desireable tension on the gas lock. Here is a picture of where my gas lock became hand tight...

I tightened it up the rest of the way with a gas cylinder wrench. It is quite tight but didn't require a lot of effort. I did slip once while tightening the gas plug and put a nice ding in my muzzle brake...dang it!...(I cut the shim at a 45' angle for the install rather than remove the brake) But is this tension about right?

I really like how my front band is tight and immobile now and not flopping all over. I also gained a nice shim-width clearance from the stock and front band, just the ferrell and the bottom of the band make contact.

On a side note, I discovered a slight rub spot inside the stock where the op rod was making contact and I used a razer to scrape it down. Should help.

I've done all of this plus a NM spring guide install and I was getting just shy of 3" groups at 100yards open sights before so I can't wait to hit the range and see how all of this affects my group size. I'm really enjoying this tinkering around.

Thanks for the help!!!