How common is a Sig hammer fired pistol with offset primer strike? I have three with primer strike that is noticeable off center; 1911 STX, P226 Legion and P229 SSE. None have been an operating issue, but curious.

SIG, I haven't noticed, but these are fired cases from a Beretta Nano. No ignition issues.

It's fairly common to nearly all makes. Not an issue, as long as the pin fully strikes the primer, not part of the casing. I've seen that in some old, very beaten up guns. Never took the time to investigate it, though.

That's close enough for government work!

I just went and looked in the two cans of 9mm and 357 Sig caliber spent brass I have... in looking at about 6-10 of each, I only found one that looked close to 'on center' and that was actually a .380 round accidentally in with the 9mm's.

the picture that Psra posted above might be misleading ... first you should only compare the spent brass from one gun which this is, even though it looks like the firing pin is moving around I'd bet it is hitting in the exact same place on the primer each time...albeit 'off center' slightly.

Way back I shot on a Marine bullseye team. Guns were from Quantico and consisted of a gun box, a S&W Model 41, an accurized S&W revolver in .38 Spl, and a fully accurized 1911. It appears they were taken off the line and "fixed up". Among the numerous things done to them was a welded piece on the slide to move the rear of the barrel laterally as needed to center the pin strike. ONLY pistol I ever encountered that. Those guns were really, really accurate - lots better than we were.

I had a stainless Colt Gold Cup Trophy in .45 some years back that had a significant primer strike offset. It was a $1300 - $1350 item at that time. It is $1699 MSRP today.
Link: https://www.colt.com/detail-pa...ue-g10-grips-o5070xe
I just looked at the date on my photo, May 2011. It's amazing how time flies! (my photo at bottom of this post)

I purchased that Gold Cup Trophy brand new, and had a local FFL order it in for me.
The first time out shooting that pistol, one of my shooting friends happened to pick up one of my fired cases and noticed the significantly offset primer strike.
He was qualified to make that assessment, he worked for a number of years assembling Dan Wesson handguns.
He asked if all the brass laying on the ground was mine. I wasn't sure so he caught the next three ejected fired cases in mid air.

I called Colt Customer Service and had a rep tell me it wasn't possible for the primer strike to be so far offset, that I was being overly critical. The rep stated I was exaggerating.
I asked the rep for an email address so I could sent her a photo.
Within minutes of emailing the photo, I got a free return shipping label and then sent it back to the mothership for service.

When the Gold Cup Trophy was returned, the paperwork said that the slide had been replaced.
I returned to the range and test fired that Gold Cup Trophy again and there was no noticeable improvement on the primer strike offset.

There are not that many things that will cause an offset primer strike on a 1911 pistol.

The frame can be out of specification. The slide stop pin hole location can be out of position.

The barrel can be fitted incorrectly. The locking lugs/barrel feet can be fitted incorrectly.

The positional location for the drilled hole in the slide for the firing pin channel can be mislocated.

Ultimately I got rid of that Colt Gold Cup Trophy, however it was accurate and reliable.

But something was wrong with the way it was assembled/manufactured at the Colt factory.

I didn't want to be the one holding onto that steaming bag of poop.

My Dan Wesson Pointman 9 1911 has perfectly centered firing pin strikes so I now know it's possible to do better than Colt did.

That particular Gold Cup Trophy was the last Colt that I purchased. I don't believe there will be another.

I have been told that for top tier Bullseye competition, they will deliberately assemble a 1911 pistol with a very slight primer strike offset.

The claim >allegedly< is you will get slightly less velocity variation when the firing pin hits the primer slightly off the "point" of the anvil in the primer.

However, that just may be an excuse for improper build techniques.

In my case, the offset was significantly more than slightly offset.

You be the judge.

Gold Cup by cee_Kamp 32ACP, on Flickr

Interesting, I have owned literally 50+ SIG classics over the last 20+ years and have never run into this, I was just looking through brass for a P229-1 type I have and it looks normal not off center.