Well, I've owned this AR for at least two years now. I have put enough rounds through it to know that it cycles without issue when shooting unsuppressed and in the unsuppressed mode. Using my friend's AAC suppressor, it cycled flawlessly in suppressed mode. Using it with my Surefire SOCOM556-rc suppressor in suppressed mode, the damn thing doesn't cycle and continually has FTEs and FTFs. It's not getting enough gas in this mode. Has anyone else heard of any issues with the Sig 516 and Surefire suppressors? I never have any issues with my 11.5" BCM upper and my Surefires, but that's a direct gas upper. I was quite pleased with the Sig up to this point, but it's not worth much to me if it doesn't work with a suppressor considering that's the whole reason I bought it. I have yet to contact Sig, but I was curious to see what y'all had to say. I appreciate any help or input.

How's it cycle with the gas regulator set on the middle setting?

It has had malfunctions when suppressed and on the normal setting. It also has significantly more blowback in that setting.

How's the blowback with the Surefire can on normal compare to the AAC on the suppressed setting?  Also, I don't remember what buffer SIG uses in the 516.  Is it H?  Maybe try a standard 3.0oz buffer and see what that does.

Really, unless the gun is cycling so hard it failed to feed or starts to stovepipe I don't think I'd be too worried about it.  But it wouldn't hurt to call SIG and see what they recommend in your situation.

A lighter buffer might work. I know that it is definitely "over gassed" with the Surefire in the normal setting because it's destroyed both bullet and brass trying to feed it in that setting. I know it's the rifle and not the ammo because I've tried everything from basic 55 gr. brass ammo to 64 gr. Nosler and Varmageddon. I think I'll probably end up calling Sig to see what they recommend. Main frustration comes from the fact that I bough the gun to run suppressed and that's the one thing it doesn't do. I think the Surefire doesn't create enough back pressure for the suppressed mode to cycle.

Well, try a light buffer if you have one. Otherwise I would just send it back.

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So it runs just fine with your friends AAC suppressor but not with your SOCOM556-rc and you think it's the gun?
I have both a 16 inch 516 and a 10 inch 516 SBR. Both run great on the suppressor setting  with a Gemtech Trek, but only run on the normal setting if I use my Gemtech  Quicksand( 308 can). I'm thinking the  answer lies with the  SOCOM556-rc, maybe you should call them and not Sig. Maybe the can was designed to allow less back pressure into the barrel  of DI system guns so the DI guns will run cleaner than normal when suppressed. I mean DI guns get dirty real quick when ran suppressed. Designing a suppressor that caused less dirt to get into the bolt/bolt carrier/barrel of a DI gun  and still suppressed sound well sounds like a good idea.

A 5 second Google search for SOCOM556-rc confirmed what I just said about less back pressure. Your going to have to run the Sig 516 on the normal setting to get it to work with the SOCOM556-rc. That's the way the suppressor was designed.

I mentioned the back pressure thing in a previous post. I guess I'll have to toy with buffers then.

If yours is the 16" patrol model, and if you have access to an LWRC bolt carrier, try running that in your SIG 516 as I can confirm that the original 516 bolt carrier's weight is exactly the same of the LWRC bolt carrier. The updated 516 bolt carrier is almost 2 oz lighter than the original 516 design. Good luck!

I had the same issue trying to run my Surefire 762K legacy can on my 10.5 516 in suppressed mode. It turned into a single shot. I tried my buddies Surefire 556 Mini legacy can and it runs like a champ. I was wondering if i purchased a new Surefie 556 Socom would it run with the reduced back pressure. I guess you answered that question for me.

I shoot with the same settings with and without the GemTech G5 suppressor.