Does anyone have a Sig 516 with a 10" barrel?  I started out looking for a P556 to SBR. After doing a little research, I find that I can get a 516 upper, attach it to my already registered SBR and head to the range.

I'm wanting to know about reliability, function, and accuracy. They are expensive, but I can go this route and save about $400.00 and avoid the traditionally long NFA wait time.

I have a factory sig 516 10 inch SBR. Great gun. Bought it to run a Gemtech Trek on it all the time and have a piston driven vs Di gun to cut down on the amount of crud in the upper receiver that comes with running a can. It's worked 100 percent of the time and never let me down. Prints nice little 1/2 inch groups at 50 yards with a AimPoint Pro and 77 grain MK 262 ammo.

I have the Sig 516 10" in an SBR already.

Shoots like a dream, aside from wiping the bolt off, I am trying to get the gun to fail. I'm at 3500+ rounds without a good cleaning. it holds a 2" group at 100 yards off a lead sled with a magnified optic.

In the case of the 516 is the lower the registered part, or is it like the 556 where the upper is registered? I already have registered SBR's and if I can just pull two pins and swap to a piston upper, it would be GREAT!

The 516/716/M400 family are all lower receiver registered.

Thanks for the info. My credit card bill is about to go up. Have you got any experience with the 516 10"?

That looks like a quad rail. Are there any other options for hand guards?

They don't exist? Explain please? I looked at Lancers website and they are EXPENSIVE!  

I'm on the fence right now and have been looking at three different Sig forums for information. SBR length barrels are not mentioned in any of them, but apparently there have been quite a few reliability issues. Most seem to be traced back to ammo. The users are saying that as long as you use 5.56 spec ammo (not .223) everything works fine. But if you use .223 or reloads, it has numerous FTF and double feed issues. I really want a gas piston SBR, but I'm concerned about function and reliability especially with the shorter barrel. I do quite a bit of reloading to feed my habit.  I have a 556 Classic and have had zero problems with any and all ammo which is what led me to want a gas piston SBR.

I just got off the phone with Sig CS and asked about their 10.0 uppers and if there were any problems with them using reloads. We were about two minutes into the conversation and the guy says "yeah, we have those in stock and I can get you 20% off the listed price". Then he tells me "to his knowledge" there have been no issues with ammo. Now, with that discount, I'm thinking about getting a 10.0 AND a 7.5 upper.  Decisions, decisions.

I have one in 7.5 ,10 and 16 inch.

Probably the most under rated out there.

Can you tell me anything about function and reliability? What ammo are you using? Any reloads at all?

No reloads.

I only shoot Nato surplus 62 gr ss109 and M855.

Function is 100 % all the time , every time.

I'm focused on reloads cause I have several thousand waiting to be shot. My 556 Classic has functioned perfectly with every round I've ever put in it. No matter if it was the cheapest Wolf that was on sale, my reloads or quality Lake City issue. As said earlier, my 556 and the gas piston system is what drove me to want a 516 upper for my SBR. I want that same quality and reliability in this upper. Just trying to do some research and get some range reports before I get the card out and make the call.