Unable to Zero 556 SWAT Classic

[mobius002]

I purchased a 556 SWAT Classic a few months ago and on my first trip to the indoor range I belonged to I was shooting way low, about a foot at 55 feet with the diopter CQB sight setting. I know this was too close to really zero the rifle but I thought that was way too far off. SIG sent me a new diopter rear thinking that might be the problem, and today I took the rifle out to a 100 yard outdoor range with the new sight equipped ready to zero this bad boy in.

I'm no expert marksman by any means but I was shooting from a bench and I had 10 rounds within about 4 inches at 100 yards, so not a terrible grouping, for me at least. The problem is that even with the windage cranked all the way to the right and the elevation cranked all the way up, the thing is shooting about a foot low and 5" to the left. I have other rifles that I have had no problem putting on the black so I know this issue is not my own lack of skill. Basically what I am wondering is if this is a known issue? I plan on calling up SIG on Tuesday for an RMA to get it checked out but is there anything I would be able to do myself to fix this?

I'm pretty pissed that I spent all this money for a rifle that won't even shoot straight.

 

[xfyrfiter]

Sounds as if the front sight may be canted to one side.

 

[918v]

Could be a bent barrel or a bad mount.

 

[Tommygunn]

If you're shooting with the Sig rotary diopter sight, those are notorious. They look nice but they occasionally just won't work right.
I have the 556 Patrol, and when I had the diopter it too shot low. Probably part of the problem was lack of a really good LONG range, but even adjusting it didn't work; in fact the sight tried to spontaneously disassemble.
My solution was to get a Midland Industries front sight (folder) which is used on the Sig 556 when BUIS are used, for the AR style. Then I bought an Eotech holo sight.
At this point I still have the fine tuning to do.
I tend do doubt that your front sight is canted or anything ....but it can't hurt to check it just to be safe.

 

[BADUNAME37]

You are moving the rear sight in the opposite direction you want to move the bullet's POI, correct?

If you want to shoot higher, lower the rear sight. If you want to shoot more to the right, move the rear sight left.

 

[mobius002]

Sorry Friendly Don't Fire but I think you have it backwards. I am adjusting the rear sight to the right and up to try to shoot higher and to the right from where I am hitting the paper. If I am wrong then this could easily be my problem but I'm pretty sure it isn't. Can anyone vouch for this?

 

[Ramone]

Friendly has it backwards.

Are you using good ammo? 4" groups off the bench at 100yds is about twice what I'd expect.

 

[mobius002]

It's not the best, PMC bronze.... but still the whole group is down and to the left, not much scatter.

 

[Ramone]

If a 'diopter' is the same as an aperture sight (aka 'peepsight', like the standard AR15 iron sight), are you putting the front sight post in the center of the aperture?

is the front post adjustable?

 

[mobius002]

The circle around the front sight is aligned with the edges of the rear peep sight so that they form one circle, with the top of the front sight post in the center of the sight picture. I am fairly certain this is how the sights are supposed to be aligned. The front sight post is adjustable for windage but appears to be centered fairly well.

 

[Ramone]

Okay, that sounds good- just remember, never look AT the rear aperture- look THROUGH it- focus on the front post.

if that front post looks reasonably centered, and it's not canted, I'd say it's going back to SIG.

 

[Averageman]

I had a Sig Swat 556 with very similar problems.
I sent it back to Sig and come to find out the barrel to reciever was incorrectly mounted.
The thing with Sig is that the Q/A-Q/C is so erratic you cannot depend on getting a good rifle from them.
Sig did try and make it right, you see 9 months later I got one of the first Sig 556R's. It took 9 months to make it right and it still isnt worth the time and effort I went to.

 

[mobius002]

Sounds like I am sending her back to the factory as soon as I can get an RMA. Just hoping it doesn't take too long to fix!