"This gun was the 12th airsoft gun that i have owned. I have gone from Echo 1 to JG to VFC and now to King Arms. Of all the stock V2 gearbox guns i have owned, upgraded, and tuned, this 516 seems pretty average off the bat, however, there are some little things that i found quite appealing about it.
As a tech, i feel i should start with what i am most familiar with: the internals. The barrel and Hop-Up are pretty average. Nothing really stood out and impressed me. what i did like about it was that the bump inside the bucking was shaped like an inverted "U", similar to the REAPS bucking (a cheaper and easier way to R-Hop a gun). this means that you can out-range other stock AEGs out of the box.
The motor is probably the worst part about this gun. I'm not saying its horrible or anything, but it is has ferrite magnets. Most stock gun motors have ferrite magnets (with the exception of some JG guns), but, this means it has less torque than other motors with neodymium magnets. As far as stock gun motors go... it does the job. I would suggest upgrading the motor first.
I was very impressed with the inside of the gearbox. The gears in this gun are very strong and beefy. If tuned properly, they should last you hundreds of thousands of rounds. The piston is also swiss-cheesed from the factory and you get a metal selector plate which is nice. The spring, which I assume is either an M100 or M110, is irregularly pitched, and should help decrease wear. If it came with a ball-bearing spring guide and a metal cylinder head, i would say that this gearbox would be perfect... but it doesn't... Still a very good stock gearbox though.
The wiring is very thin. It is maybe 18 or 20 awg wire. Do not use a high output Lipo with this gun if it is bone stock. You WILL fry the wire and connectors... I can tell you from experience...
As far as externals go... they are extraordinary! The trademarks on the receiver look extremely sexy and the numbers on the rails really give this gun a nice highlight. I absolutely love the way the gas block looks and the functional bolt release is also a major plus. The stock does wobble, very much in fact, but that is an easy fix: just replace it with a Magpull one. The magazine seems to be made from paper and scotch tape. It is low quality and it broke when i dropped it for the first time... not a big deal really... you can find M4 mags anywhere for real cheap.
For my entire life i have been cursed with being left-handed, but, the ambidextrous features on this gun help make me feel like i am an actual human being!!! The fire selector and mag release are a bit finicky, but not enough to take away from the overall quality of the externals. All things considered, i would say the externals of this gun are of the same quality as G&P, G&G, and KWA guns. Not as nice as VFC, but its pretty close.
After quite a bit of internal upgrades and tuning, this gun is now my primary and i favor it over all others in my arsenal. It is very easy to work with, very comfortable to hold, and very VERY easy on the eyes. Being left-handed, i cannot begin to express how happy i was when i saw that King Arms had made an airsoft version of this Sig. I would recommend this gun to anyone in the airsoft world, good or bad, young or old, new or veteran. The only thing: if you plan on using a standard NiMH battery, it will be hard to fit it in the stock. If only King Arms had put a better stock on this gun...
Note: shot roughly 1500 rounds per minute with an 11.1v 2500mAh 12C battery at 350fps with a .25g bb out of the box.