Wow, the tolerances really are pretty loose on these

[merc545 0]

After installing a Chaos extended rail on my S-12, I saw that the rail is slightly crooked when comparing it to the rest of the gun. The rear rail key went into the notch (and doesn't wobble at all), and the handguard retainer screw tightened down without any problems. After tightening it down, I noticed that the rail wasn't centered. Maybe the retainer screw hole on the bottom of the gas block is slightly off center? Anyone else have experience with this issue? Not really that big of a deal since the sights I'm getting can adjust for windage, but I was just curious.

[Shadoh 16]

Chances are your gas block is slightly canted.

[merc545 0]

Should I be worried? The slight crookedness doesn't bother me since I can adjust the rear sight, but could I possibly mess up the threading on the retainer screw hole?

[Shadoh 16]

If its your gas block, you can put the gun in a vise and give the block a bit of a twist with a big wrench. Just make sure you protect the gun from the vise jaws and wrench. I like to put the barrel lug in the vise and not the thin receiver. Get a straight edge and hold it along the side of your receiver all the way out to your gas block. Do it on both sides and measure the gap between the ruler and the block up by the front sight. That should tell you if its off and which way it needs to go back.

[JAldrich2008 28]

If its your gas block, you can put the gun in a vise and give the block a bit of a twist with a big wrench. Just make sure you protect the gun from the vise jaws and wrench. I like to put the barrel lug in the vise and not the thin receiver. Get a straight edge and hold it along the side of your receiver all the way out to your gas block. Do it on both sides and measure the gap between the ruler and the block up by the front sight. That should tell you if its off and which way it needs to go back.

 

I smacked mine with a heavy, hard rubber mallet. Same results though. Good idea with the ruler! I used a laser level shining down the sights, then I measured where the beam was at the end of the barrel.

 

**Edit to fix a typo.**

Edited October 18, 2010 by JoeAldrich

[Shadoh 16]

Well, the ruler only works if your receiver is straight )

[merc545 0]

Not that bad of an idea! I have a vise around somewhere but need to mount it to a sturdy bench. If I just leave it how it is and just adjust the sight to make up for the crookedness, is the canted gas block going to hurt anything mechanically? The only thing I can think of is the piston rubbing against the gas tube, which doesn't seem like that big of a deal.

[Shadoh 16]

You could leave it and never see any problems from it. Im betting most of the S12s out there have canted blocks and folks just dont notice it until they actually check it or bolt something on their gun that makes it stand out, like you did ). Mine was actually canted so far that when I straightened it out it covered one of my three gas ports completely, I had to drill a new one and there is still one underneath the block to this day. After three or four hundred rounds it tends to move back a bit. I think Im going to put some set screws in my gas block but havent made up my mind yet. The crazy thing is that these guns can be that far out of whack and still run fine.

[merc545 0]

Thanks for all the great advice, Shadoh. Only reason I don't want to mess with it right now is because I Loctite'd the s#!* out of the handguard retainer screw, and don't feel like taking it off right now.