Sig 516 upper for AR

[Tokarev]

With cheap Russian ammo.

http://www.youtube.com/watch?v=aAGxm_WJmKg

[Tokarev]

I've now had a pretty good chance to play with SIG's new 7" upper and wanted to share my thoughts. I really haven't bothered to try the upper for accuracy since I assume most people will be using this upper as a noise-maker or pistol upper. But I suppose I should shoot it for groups at 50 and 100 yards just to satisfy my own curiosity. If I have time, I'll mount my Leupold FireDot next week and give it a try.

Anyway, the upper is more than just a standard 516 upper chopped to seven inches. The gas block, upper and bolt/bolt carrier assembly remain the same but the gas parts are different. As you can see, the gas parts look alike when assembled with the exception of the overall length:


Note that the gas valve on the 7" model is, indeed, different. Gone are the small gas rings on the full-length system. These have been replaced with three grooves on the short system:



The piston assemblies are different as well. Note that the short piston lacks the small vent holes at the muzzle end of the cup:



The gas valve on the 7" model only has three settings. They are full-powered, suppressed and off. The upper will not run in the suppressed setting without a can in place:


Note the crazy short overall length of the 7" upper:


Even though the barrel and gas system is substantially reduced, the handguard lengths are similar. Note that the 7" model's rail telescopes over the gas block on the shorty. I like this and would like to see SIG extend the rail on the 16" model to cover the gas block. This would cover the bayonet lug but I don't think too many people would mind:


The short upper weighs roughly a pound less than its longer brother. Weights are about 4.75 pounds for the 16" and 3.75 pounds for the shorty. The reduced weight and changed center of gravity really makes for a handy little blaster.

I've been pleased with what I've seen from the SIG piston guns, for the most part. I've had good reliability from both lengths. The 7" upper runs fine in semi- and full-auto as does the 16" model. I don't care for the way SIG chose to secure the gas valves. These parts thread into the gas blocks and are held from rotation by a small detent. What I don't like is that the detent is very small and hard to depress without a cartridge or a punch and the gas valves themselves are hard to turn when fouled with carbon. I'd like to see SIG re-design the valves slightly and/or shorten the retaining detent a little so the shooter doesn't have to keep the detent continually depressed while unscrewing the valve.

The 7" upper is fun to shoot but the handgaurd's length is limiting even though it does extend around the gas block. The gas block is still exposed up top and I've found it very easy to burn a finger or thumb while shooting if not careful. A VFG is probably a requirement on such a short platform.

As soon as I can get some long range accuracy and some chrono data, I'll post an update.

Thanks for reading. Happy New Year!

[sinlessorrow]

If Eugene Stoner wanted the AR to be a 'piston' gun he would have made it one nearly 50yrs ago.
Adding pistons to ARs is akin to adding spark plugs to a diesel engine.

hell if stoner thought piston was a superior system the KAC SR-15 would be a piston design, since stoner had input in its creation

after reading this can i get some clarity on this thread?

https://www.m4carbine.net/showthread...ighlight=hk416

in it apparently the 416 is being retired, yet in this thread its not. it left me a little confused as to which is true?

[dpaqu]

Nice pics and review Tokerev. I almost wish you had started a new thread

I still wish the 556 had lived up to its older brother the 550.

[Tokarev]

Nice pics and review Tokerev. I almost wish you had started a new thread...

Please see here:


https://www.m4carbine.net/showthread.php?t=95281

[Tokarev]

One of my complaints about the SIG516 is the threaded gas valve. The threads are very fine and the detent that locks the gas valve on its settings is very small. The detent is hard to depress and the threads make the valve difficult to unscrew when the parts are fouled with carbon.

I am pleased to see that SIG has recently changed the design of the gas block and valve. The parts are now more like those used on the new SIG716 in that they use studs that mate with grooves instead of threads. This should resolve my previous issue with the threads, etc.

Now I'll admit that this is all speculation on my part. I haven't had a chance to use the new parts on the 516 but I do own a 716 and haven't had any problems removing the gas parts. Anyway, here are a couple pics of the new parts that I found on TOS:

[Tokarev]

My new GenII rifle. The new gas valve seems to be a big improvement. It isn't necessarily easier to adjust but it is easier to disassemble.

[first there]

Back from the dead! Don't complain about the weight jack some steel and man up! Love my 516! That is all carry on...