CyberVirus:
If I understand your last post you apparently intend to chamber a muzzle loading rifle for a breach loading single shot.
I would say that such a proposition would be swimming in uncharted waters. There are an abundance of warnings, by gun manufacturers, about using smokeless powder in muzzle loading rifles. The intervention of a brass cartridge probably doesn't change much. I would say that personally I would only consider it if the original manufacturer gave his blessing and I doubt very much that anyone in the industry would ever do that.
If you haven't as yet heard about Toby Bridges and his accident with the Savage Model ML-10 you should view the photos and then decide.
It isn't necessary to evaluate recoil tolerance by building a prototype. Numbers are numbers. Recoil has three components all of which are measureable.
A 3" magnum 12 gauge shotgun will outkick a 375 H&H Magnum rifle. If you have a shotgun and have shot it then you know its recoil value and your tolerance. A rifle .375 caliber won't be worse.
As you may know the .308 case is an offspring of the .30-06. You can easily acquire a .375/30-06 from Fred Zeglin. That will shoot almost as powerfully as a 375 H&H, yet still kick like a 30-06. Indeed you can go upto a .411/30-06. If you wish to peruse his site and evaluate his line you can go to:
http://www.z-hat.com/In the concept of short magnums the case is unconventional in that it it is ( comparatively ) excessively greater in diameter than customary cartridges and it is shorter. This changes the burn characteristics/performance of smokeless powders in a positive way. It burns less and produces more. Some short fat cases have proven to be exceptionally accurate to boot.
The Ackley Improved 30-06 is about 5% better than the 30-06. Fred's version improves it about another 4 to 5% so his "Hawk" 30-06 with the shoulder blown forward outperforms the 30-06 by roughly 9 to 10%.
Necking a 30-06 case up to .375, however, doesn't place it in the short magnum category. A case such as a .404 Jeffery should be considered. The .404 Jeffery is the base case for the Dakota line. In fact there is a wildcat .404/.375 which is in use on African big game and it is a real killer of anything.
The .404 Jeffery would need to be shortened to make it qualify for a "short magnum".375. The exact length would be determined by a series of calculations to determine when the water grain capacity came into equality with the desired, or design, criteria. In a sense this would be working backwards into the solution or "backing down".
This would require magazine, bolt alterations to a rifle and possibly a new barrel.
There would be the cost of a special chambering reamer and some subsequent gunsmith work such as blueing and certain selective accuratizing things, bolt lapping, trueing. Load development. Dies. Case development.
Z-Hat can handle all of that. You may want to give him a call or E-mail him.
Good Luck with your project and - Enjoy !
Bill Tibbe
