The Tar-Hunts are a rear locking lug action.Two lugs, and built oversize, designed for rifle pressures.And the A-Bolt

and Savage are also designed for rifle pressures.All three will handle at least twice the pressure that plastic shotshells can handle, according to testers and comparison articles.Those three actions can operate at 12,000 lbs of

bolt thrust with about 3 multiples of safety, which equates to 33-37,000 psi loads in strong brass cases..Ed.

Looking at the boltthrust issue, there's about 4x the area in a brass 12ga case than in an '06. Even using BMG brass you're at around 3x. So, whatever pressure you'd feel running that bolt in an 06 (assume nonrupturing brass, I guess) then divide appropriately.
Seems to me even with imaginary uberbrass, the limit must be around 70k psi. That means you're limited to about 17.5k psi or 23k for BMG.
Still enough to get an 1150g slug moving at 1250fps for 4k ME from a .725" hole!!!

Shotguns operate around 12000 to 13000 lbs while rifles operate at 50000 to 60000. While both may be proofed at higher pressures there is a difference. I'm good friends with the manufacturer of the Tar-Hunt. I shot benchrest with Randy for years and he built my rifles. I would suggest you visit the Tar-Hunt website and contact Randy. He has done a LOT of pressure testing. There is more to a receiver than how the bolt locks up. Heat treat can make a big difference.

If someone can give me ALL the bolt dimensions I can calculate the shear stresses. Of course, that is only HALF the problem. I strongly recommend not to over-pressure any of the 12 gauge shotguns, bolt action or otherwise, on the market today. They were not designed for it, and the consequences of this folly could be tragic!

For background:

30-06 loaded to 60,000 psi has a bolt thrust of ~ 7550 lbs

12 gauge loaded to 11,000 psi has bolt thrust of ~ 4500 lbs

Those are the design envelope parameters for those cartridges and the guns made to fire them.

A 12 gauge shotgun loaded to 37,000 psi has a bolt thrust of 15,200 pounds! Over twice what a 30-06 @ 60,000 psi has.

A 460 Weatherby mag loaded up to 63,000 psi only produces a bolt thrust of 13,400 pounds , which is approximately 85% of the 12 gauge at 37,000 psi.
Recall, that Weatherby developed a new action, the magnum sized MkV, to handle the 460 class of magnum since the mauser style action (dual opposed lugs on a .7" diameter bolt body) was NOT strong enough!

To put it bluntly, you need an action designed for the 50 BMG class of cartridge to handle 12 gauge shotguns at high pressure!

I hope this entire discussion has been only theoretical in nature to kill the time, and not sincere in any manner whatsoever!!

Scott

I'm sure, but particularly the Savage I'd imagine is as straightforward a conversion as possible, for manufaturing simplicity.
But I can't imagine they just opened the botlface up to .80 or whatever. Maybe they make a fatter bolt, in which case they may have significantly reduced lug bearing surface, or who knows whoat else and how.
Never seen one.

Savage has an extra lug like A-bolt so it is strong.With a good brass case they will handle the 12GA FH at 25-35000
psi.The Browning A-bolt handle magnums,10-12000 lbs thrust
I mean the Savage rifle can handle magnums that can put
10-13,000 lbs thrust on the bolt,and the 12Ga FH will put
10-11,000 lbs of thrust.Thrust is figured by base area times pressure, times a factor, that figures in what the sides of a good brass case, subtracts from base area, and subtracts what the part of the thrust the side takes..Ok for 55k loads a good,working,simple,
factor is .7--or 45k loads it is .65--andfor 35k & lower
loads it is .6...IE at 35k the case is taking more of the load percentage wise,than at 55k..12GA Fh base is .51 sg in
times 35,000, times .6 equals 11,000 lbs of bolts thrust.
A 25,000 psi load would have 7700 thrust.A 30,000 load
would have 9200 thrust.Now to go up 50-6ok loads and more, yes you need bmg size action...Ed.