12 bore rifles were quite popular at one time during the late 1800's. Ross Seyfried just did an article on one a couple of issues ago in Rifle Magazine. Your father is smarter than you are giving him credit for. I think he knows what works and you don't.

I smell a blown up shotgun in the future.



Shotshells run at 15,000 psi or so, and the shotguns are designed for such.



Stoke up a brass shotshell with a big cast bullet and a handfull of powder and you are into 50,000 psi real fast. You will have two projectiles: The bullet coming out of the front and the bolt body coming out the back, plus metal shards from the burst barrel wiping out the bystanders.



Ain't much use in trying to make a stopper out of a shotgun: Not enough energy. Stopping rifles begin at 6000 ft/lbs.



There is a big difference in today's shotguns and the "Real" big bores of the past that used 8, 10, or 12 bore bullets. One of these rifles from the past would make a fine stopper, but not up to the task as well as a cartridge with modern bullets, like a 458 Lott, 500 A Square, 500 Nitro, etc.

I did a stress analysis on a 45/70 handi rifle and I knew it was stronger than the brass.



So when I saw a similar design Steven OEM 410 break shotgun for $50 at a gun show, I knew just from looking at it that it was stronger than the brass. I used it to verify that 45 Colt brass could go past anything a 454 Casull revolver would survive.



I have a Marlin Goose Gun that is a 12 ga bolt action.

I would like to use it for an experiment involving a barrel extension and some hyper pressure but low powder charge loads ala quietgun.com, but the action looks too weak. It has no lugs, only the bolt handle stem in a slot in the thin tubular receiver holds the breech face.



I have tested allot of guns with overloads to see what happens, and I concur with Ackley, the breech face is not what goes, the chamber usually splits from hoop stress. I will probably use the Marlin and work up some 10 gr. loads with compressed powder and see if he chamber splits or the head space increases. The gun has been sitting in storage for 5 years waiting for the experiment, and I have no other use for it.



--

A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian.

Well, one thing, the guy's got some 20 years of handloading experience, and he's not aobut to blow anything up.
Question is more whether he'll get anywhere near where he wants to be before he gets into high pressures.
What is "high pressure?" Has no one done proofing of any of these (Marlin, Mossberg, Savage, eg.)?

So, John, mayeb "stopper" isn't the right word.
Those old .475" Nitro cartidges barely broke 5k, right? Let's just call it "$300 bigass gun."
And besides, my armchair research shows you should be able to get a 1200g to go around 1200 fps for under 12k CUP using around 100g 4895 or similar.
What do you think of that?

I think that's what the intent of the original question was to find out just how far you can safely go in a bolt action shotgun. If you are planning on useing the 50BMG brass, then I think that would add some strength to the chamber area. Didn't Browning make an A-blot 12ga slug gun that had twin locking lugs? Mid to early 90's?? I think I'd look that direction.

A 12 ga a 15,000 psi is .729" in diameter.
That bore with driving a .475" bullet in a sabot exerts 36,000 psi on the base of the .475" bullet.

That peak pressure will not be for long with a straight wall, and the Remington sabot 385 gr slug does 1900 fps, which is 500 fps less than a 470NE could thow that weight at 39kpsi.

For the 12 ga to catch the 470NE, the pressure would have to be raised to the 25 kpsi region.

SAAMI requires shotgun proof loads to be between 1.55 and 1.7 times the max load. That is between 23 and 25.5 kpsi.