Ok I am not a 1911 expert by any stretch. I own about a dozen currently and about another 12 have pass through my collection at one time or another including a original Sig GSR.
The first thing I want to point out is that the majority, I would put it at about 90% of feeding issues are mag related. I believe you have a mag related issue but pics of the actual malfunction will help to truly diagnose the issue. The fact it runs 100% with some mags and only fails with others is a clue. If it was truly a lemon it would be failing with the mags in the same manner however you are describing 2 different failures with only some mags.
American1776 said:
In the first few magazines, I had two FTF. These occured with the the 7 rounders. After that, heres what happened.
Knowing exactly what kind of FTF would help.
Fishslayer said:
There is a whole load of info on the web re 1911 extractor testing & tuning. The tension test is pretty straight forward and you can decide for yourself how to deal with it.
Take your pick.
https://www.google.com/webhp?source=...extractor+test
This is a Sig 1911 and it uses an external extractor similar to the S&W 1911s so IMHO you can ignore all the advice about extractor. You cannot remove it and it is not a user serviceable part like the GI internal extractor. It does not suffer from the same issues the GI extractor does and none of the tricks of the trade used to get a GI extractor functioning properly applies to these external extractors. This is one of the reasons I do not buy Sig or S&W 1911s.
My advice is don't polish anything. It is not the feedramp. It is not the slide stop. You do not need to replace the Sig MIM part unless it fails. If it fails have Sig send you a new one under warranty. The MIM Sig initially used was poor quality. These days it is decent and unless you are going to change out the rest of the MIM I would not bother. Also inspect the slide stop for wear or damage. I suspect in a new pistol you won't see any. There is a chance it is out of spec but with MIM parts this is less common than tooled steel because of the process used to manufacture them.
It is the mags IMHO. The factory mags are checkmates. They are decent 1911 mags. I prefer Chip Mccormick Power mags, or whatever they are calling them today, but the Checkmates should be fine.
I would inspect the Wilson mags feedlips. Are they ETMs or 47Ds. The 47D 8 rounders are the worst mag that Wilson everp produced IMHO. It is basically a 7 rounder with slight follower modification to allow you to cram 8 in there. As a result they suffer from premature spring fatigue and feeding lip deformation.
I would definitely get back to the range and fire the gun with the factory mags. I would also inspect the Wilson mags that work vs the ones that don't and see if you can detect a difference. If they look the same but continue to fail in the same manner swap the guts from a working Wilson into a failing Wilson.
-Do the follower first. Fire and see if the failures continue. If they go away then it is the follower.
-If they continue swap the spring. If they then go away you have a spring issue.
-If the new spring and follower still fail in the same manner its the tube, more than likely the feeding lips.
For the mag which does not lock the slide back look closely at the portion of the mag which engages the slide lock. Look for deformation or excessive wear but weak spring tension can also cause this failure. Remember premature spring fatigue is an issue with 47D mags.
I am willing by doing this you will find a combination that will correct the issue and lead you to a solution. If nothing solves it call Sig for customer support and send it in especially if you have trouble with the factory mags. Good luck.