What the Heck is happening to my Sig 556!

[ejfalvo]

New Sig 556 SCM, 3rd time to the range. 2nd time this problem has happened. 100 yards, sandbag, Brown Bear 62 gr ammo, Sig diopter rear, hooded front. Cool, clear, windless day. Figure 1 hour from first shot to last.

First string of 10 within 2 inches, I'm happy. 2nd string of 10 spread to 5-6 inches. 3rd string, 8-10 inches. Switch ammo, Pavi 45 and 55 gr - same issue, Another 10 of Brown Bear, I couldn't hit the 8 inch target.. One round hit the target sideways!

Any thoughts would be appreciated. I've sent 4 emails to Sig over the last 3 weeks and no response. Very frustrating.:banghead:

 

[jerkface11]

Sounds like one of your sights is loose.

 

[kirklandkie]

my initial thoughts were the same as jerkface11's, but noting that you said "One round hit the target sideways! " you've made me wonder as well. with this in mind, was it a specific weight of bullet that was hitting the target sideways? perhaps it just doesn't like that ammunition

-kirk

 

[Mot45acp]

Sounds like one of your sights is loose.

Every gun owner should have 2 tubes of blue Locktite. One on the work bench, and one in the range bag.

 

[rcmodel]

Either your barrel is almost stopped up with copper fouling.

Or, your sights are falling off.

Might try using some decent ammo too.

rc

 

[browningguy]

Sounds like extreme copper fouling if you have bullets hitting sideways, sights wouldn't have anything to do with that.

 

[Kurt_D]

If you had rounds truely hit sideways there's a serious issue with the barrel and need to CALL Sig C.S. about a RA not e-mail. In the mean time check to see if there's any marks on the flash hider that indicate a strike. I couldn't see copper fouling unless you've really put some rounds through the rifle in the past 2 tripps.

Groups opening up after the rifle gets hot isn't unusual as this isn't a HB and is piston driven. However, that's a bit extreme. Could be a loose rail or loose sight (front or rear); both have been know to happen. These guns also don't seem to like lighter, < 62gr, loads. Last, it could be the shooter getting tried and not as patient after the first string.

FWIW, my Sig seems to like the 62gr brown bear ammo, followed by the 62gr IMI M855, then Win M855 (started opening up, this was old de-linked stuff), and last the 55gr Guat (which really opened up). I too was using a Diopter sight and also ATN reflex. I was more consistant with the ATN, although I did alright with the irons.

 

[gga357]

How well can you see the rifling. There might be a defect.

 

[green country shooter]

clean barrel, locktite sights, use decent ammo
then send it back

 

[Runningman]

Are you letting the barrel cool off completely between strings? Or starting each string from a hotter and hotter barrel? Thinner barrels can really open up groups when they get hot. That is the main reason I prefer HB profiles.

 

[cgali]

The keyhole shot might indicate you should stay with 55gr. to 77gr. The sig is 1/7 twist barrel. The 75 gr. is optimum according to several on the sigarms556.com forum. Jacketed boat tail hollow point Privi 75gr. is nammed quite often as being a good round in the Sig.