Having watched many shooters over the years shoot to different points of aim ... using the same pistol and ammunition ... I've come to be a bit conservative in making assumptions and guesses.
I prefer to be present when the shooter is actually experiencing the reported 'sight alignment' issue ... or feeding issue, or whatever issue is being reported. I prefer to observe the shooter while he/she is shooting the gun. I like to shoot it myself, using the same ammunition in the same condition as when it's being used by the shooter (checking for maintenance, ammunition and even environmental influences present at the time the issue is reported as being experienced). I even like to watch other folks shoot the same gun and ammunition at times.
Why?
Because I've solved more 'gun problems' by correcting a shooter, maintenance or ammunition-related condition than I have actual gun problems.
Break in?
Some relevance. Not all newly assembled machines are free of burrs, sharp edges or sometimes a bit of a rough surface between two or more working parts. Sometimes it's more of a break-in period for the shooter, though.
Sometimes some folks don't clean their NIB pistols (AND magazines) and remove the excessive amount of factory applied packing lubricant often present in NIB firearms.
Sometimes they don't lubricate NIB pistols, either. Sig Sauer pistols are considered 'wet guns' for a reason, too. The instructor in the Sig Sauer pistol armorer class repeated that almost as a mantra throughout the 2-day class. There was even a fill-in-the-blank question on the written test regarding how to determine whether a Sig Sauer pistol was properly lubricated, and the correct answer had to be something along the lines of being able to verify the presence of lubrication by
touch &
sight.
One time I watched as a pair of experienced firearms instructors each experienced a single failure-to-feed with a pair of NIB P220 & 226 pistols, using duty ammunition, within the very first magazine load in each pistol. Each pistol had ONE feeding problem right away. Granted, they ere fired right out-of-the-box, with factory grease oozing from the pistols and excessive oil present on and within the magazines. They functioned fine from that point onward, though.
An excessively 'wet' (oil), gooey magazine & follower can sometimes slow down the normal freedom of movement of rounds in the magazine, though, and could potentially affect feeding. Much like a very dirty magazine which has been contaminated with fouling, debris, grit, sand, etc.
Some folks aren't comfortable with the grip dimensions of the typical Sig Sauer pistol. Others may not be as comfortable as they might expect with the traditional double action trigger operation and weight, and may shift their grip a bit while shooting, which could lend itself under the wrong circumstances to grip-stability related feeding and functioning issues.
If someone thinks the sights are drifted so far off that the gun is shooting noticeably off to one side, I ask them to shoot the gun to the same point-of-aim ... using their other hand. If the gun shoots to a different point-of-impact it gives me something to consider while continuing to diagnose things.
I've found ball & dummy drills done unexpectedly can sometimes yield some insight, too. If the shooter actually feels something unexpected or unintentional occurring to them when they're expecting recoil it can help them understand what's occurring, which is the first step toward correcting something (and it helps them accept that it's really happening, and that it's something within their control to change).
Sometimes folks familiar with one, or even a few, handgun designs might find themselves experiencing noticeably different results when shooting a new and different design.
Dunno about the case marking. Have to see it and think about it after examining and trying the pistol & magazines using the same ammunition.
Just out of curiosity, is this one of the P220's with the second of the internal extractors, or the newest external pivoting/plunger design (like the other calibers presently use)? Some feeding issues can be caused by an extractor, and the previous internal tensioned extractor in the American-made solid machined slides did require some attention upon occasion. Even a pivoting extractor could have a potential issue if there was a burr or other condition affecting the operation of the spring-powered plunger or the condition of the extractor hook itself. Things have sometimes slipped through QC before, and likely will again.
FWIW, we were told in my armorer class that sometimes a new 220 might have a tight fitting barrel (in the slide), illustrated by occasional feeding issues occurring with the first 150 rounds. We were told the tight tolerances could be resolved by either 'seating the barrel' (involves the use of a brass hammer applied in an appropriate manner
) or else it might resolve itself as normal wear occurred.
Advertising is just that ... advertising.
Warranties, spare parts and service technicians exist for a reason, you know ... just like service departments and service technicians in car dealerships. It may be frustrating, but it won't do any good to remain frustrated.
Sig Sauer has some good folks and a good reputation. I'd have confidence in their customer service. You could always call back and ask to speak to someone else (if the same person ends up on the phone) ... politely & nicely ... and explain your experience and concerns.
Just my thoughts. I'm not there and I can't know what's happening, or not happening, with your particular pistol.