I'm thinkin your gunsmith is biased against pumps for some reason. They are easy to load for and will accept surprisingly heavy loads w/o problems. Sounds like a resizing die problem.
Are you using small base dies? Although they are recommended for pumps and semis, I've never needed them for pump rifles. A regular FL resize die will work fine w/o any of the problems you describe.
The gunsmith was the fellow whom sold me the rifle and spoke very highly of them, so no, not too biased. He had indicated that determining headspace on these was a bit of a challenge. On the first rifle, he found that headspace was ok. After that I loaded brand new "virgin" Win brass with 85 gr nosler loads. Very nice consistent groups. After first firing, the shiny ring appeared. After second firing of the 20 I loaded, 9 were already split about 1/4" from the head. It was at that point he suggested to send to Gravel's. They replaced rifle with another great shooter. Same brass issue.
Traded rifle off. Maybe it was a particular production run of those rifles, I dunno. I have a buddy whom had a slightly older one, no issues at all.


















































