I've been trying to work out some issues with my Sig 556 Swat. It shows some promise of good accuracy but it's had a wondering zero. It would sometimes cluster shots together and then wander right and left all over a target.

The first correction I tried was to releive the rails where they were binding on the receiver. The rail sections were tight against the sides of the receiver so on both sides I removed enough material so that they didn't touch the sides at the front of the receiver.

Then I went to the range. For whatever reason the 1st shot out of a mag or hand loaded into the chamber hits 4 MOA to the Right of the remaining shots. Here's a 100yd target:




6 first shots either from one of 2 different mags and a couple shots without a mag and the round handloaded into the chamber and the bolt allowed to slam forward shot an 1" group 4 MOA to the right of the remaining shots.

The 1st shots were more consistant POI than the remaining shots. 1st shots were MOAish and the remainers 2 or so MOA (There were gusts up to 20 mph.).

The rifle is a SIG 556 Swat with the factory rails and an Aimpoint M-4 sight without magnifyer.

It used to vary right and left, now it seems to be just right. Maybe one of the rails needs more relief room from the receiver????

I'm going to check the rails to see if during firing they might be bumping the sides. And releive more if needed.

It shouldn't be the mag related because it shot a tight group using shots from 2 different mags, a P-mag and 20rd Universal with aluminum follower and even without a mag and the round placed into the chamber and the bolt allowed to slam forward.

I don't think it's the optic or the mount because it shot a tight consistant group on 1st shots. 1" for 6 shots is satisfactory for me with a unmagnified red dot site at 100yds.

Has anyone ever experienced anything similar? I thought to try std handguards but I bought that model to have the rails and hope I can get them to work. Any other idea's or suggestions?

Thanks for any help, I'll report back if I find a solution.............................DJ