Re: Opinions on Sig Sauer 556
I just ran a few rounds through a new 556 SWAT this past weekend and checked a few numbers last night. I hadn't planned on posting this here, but you may find it useful.
The Sig 556 SWAT (16" barrel, 1 in 7" twist) was put through a barrel break in procedure as previously described for the Sig 556 DMR. Using a Nightforce 3.5-15x50 NXS (F2) scope with a LaRue QD mount and a Lead Sled Solo, 25 rounds of each ammunition were tested. The first 5 rounds were used to sight in, followed by 4 x 5 round groups. A Chrony Beta was used to measure muzzle velocity for 10 shot strings (placed 10 feet from muzzle per the directions). All ammunition tested except the Hornady 55 gr SP and Fiochi 62 gr FMJ were Match grade. Weather conditions were excellent (sunny, 80 °F, very little wind).
The maximum spread for each 5 shot group was measured (center to center) and the mean ± standard deviation determined in inches and MOA as shown below:
Frankly, I'm a little disappointed in these results. I also have a 556 DMR, which I can easily group at or below 1.0 MOA using the exact same scope, benchrest, etc., under identical conditions. I had hoped this rifle would group more in the 1.0 to 1.5 MOA range. As pointed out above, it may be this specific rifle. I have another identical one that I put through a barrel break in, but haven't done any kind of accuracy test as yet.
I bought these rifles for the purpose of taking a carbine training course, because the instructor (appropriately I think) would not allow me to use my 556 pistols. I'm a big fan of the reliability of the Sig gas piston system, and having several 556 pistols and rifles where the main upper/lower sections and bolt/carrier are virtually identical has its merits.
But as pointed out above, these are fairly heavy rifles (10-11 lb loaded, w optic and bipod), especially in the front. The SWAT patrol version with the short (556 pistol length) piston is supposed to correct the front end weight to some extent. Regarding the handguard comment above, I have weighed both the plastic (fishgill) and the Sig factory aluminum quadrail. The plastic guard was a hair over 14 oz., and the factory quadrail was slightly heavier at just under 17 oz. I checked because the quadrail felt a little heavier on the rifle, but I wanted to add MBUS instead of the steel hooded front sight/rear diopter and the fishgill handguard doesn't have a rail on top for the front.
In summary, I think these rifles will do the job for the purpose I bought them, but I do wish the accuracy was a little better. As already stated, they're tough and reliable, but a little heavy and hard on brass. So like everything else, it really depends on exactly what you want/expect out the weapon. Hope this helps you make a more informed decision.
