I will try to reply to everything. If I miss something let me know.
All of these rifles were bought used. Though, all appeared as dang near new, literally.
So, I am assuming the throats were as factory reamed.
The MRC magazine is a nominal 3.6", perhaps a tiny longer. I actually load it to 3.5960" to allow me, real or imagined comfort level on COL and ogive variations.
The Winchester Model 70 Super Express throat surprised the heck out of me. I measured, re-measured and Re-measured ...
But, they came out consistent. This one may be a potential candidate for one of the spare 3.6" replacement magazines that I have around here. But, I will probably be putting it in a fiberglass stock, before the additional recoil. I would say throat erosion is not a factor on this one. It literally looked like new. I think I got 2 or 3 boxes of the Hornady super-whatever 500 grain with it, missing with 2 or 3 fired brass in one box.
The CZ had a trip to AHR prior to my purchase. But it also looked new. Now that one, I never bothered to measure. I shot some factory loads through it. I sort of did, but realized the 450's were dang near out of the brass, and the test COL cartridge from the MRC at 3.8205" worked through the magazine without issue. And called it good enough since all my Lott loads were for the MRC. Heck, I just "assumed" it was a SAAMI Winchester throat. Which would have been no issue with the MRC loaded lengths since I was not looking to maximize it.
Edit: I had a picture of the AHR work order on the CZ. No chamber work was listed.
