Rex,
My 9.3x62 is a custom Mauser built on a VZ24 action with a Montana rifle co. barrel. It does not have a long throat. I assume the reamer was sammi spec?[/quote]

Thanks for that information sir.
That would not have been cut with a SAAMI-standard reamer. In fact it is far from it (and there is not necessarily anything wrong with that).
Too big to attach the individual drawings, but you can reference the most recent SAAMI cartridge dimensions on their published centerfire rifle document HERE
The 9.3x62 is on page 56 (.pdf page 68). Note the chamber drawing at the bottom of that page. The 9.3x62 has an unusual, very long and tapered throat. Doing the math (3.555" - 2.453") shows a 1.102" long throat, which is in a class by itself among common rifle chambers.
You can contrast it to the 30-06 shown on page 95 (.pdf page 107). The 30-06's throat is only .2214" long (2.7442" - 2.5228")

Your rifle has an extremely short throat compared to SAAMI. From your earlier photo I recall the Privi 285 jams the lands at 3.20" (or thereabouts).
In a SAAMI chamber, the throat doesn't taper down to the basic bore/groove until 3.555" from what would effectively be the case head. Recall in my chamber, the "jam" OAL for the Privi is 3.53" and for the Partition is 3.59", consistent with the SAAMI dimensions. My magazine only allows 3.4 so I load everything to 3.375" and they shoot great.
Since the SAAMI maximum OAL for the 9.3x62 cartridge is 3.291" to fit in the 3.30 in magazine of the pre-WWI commercial and military Mauser 98's it was intended to be housed in, if I were a betting man, I'd guess the smith that made yours cut a custom throat so you could load right up to the lands with most spitzers while staying at or under SAAMI max OAL.

Question - have you shot much factory ammo in it? I have factory Lapua 285 Mega (which is the identical profile to the 285 Privi) and they are loaded to 3.265", (crimped into the groove closest to the bullet base). Based on your photo I wouldn't expect these to chamber in your rifle.

Have you found that you get higher velocities than predicted in published load data?

Anyway, just casual curiosity about your rifle.
I throw the rest of the data above out mostly for the OP since, though you can fireform by jamming the lands in your rifle that wouldn't be possible in a SAAMI chamber.

All the best,
Rex

Last edited by TRexF16; 11/18/22.