If you could create one from scratch...
 

If you had everything needed to start from scratch to custom make your own caliber (money, tools, knowledge, etc) what would you create?... Varmint? Target? Large game? Handgun?

Anti materiel....

Truthfully, there are so many cartridges extant now I don't see many places for additions.

For instance, I already own a Remington 541 (I think) .22 long rifle caliber rifle, a Ruger M77-.22 Hornet' and a Remington 700 in .22-250 Remington. What other .22 caliber rifle would do what I can't do now?

About the only thing I can think of that would be 'useful' is a modernized version of the .35 Remington round; in a modern semi-automatic rifle. And that's been done - the .35 (or 9mm) x 39 round. It's the 7.62x39mm Russian (AK47) round, necked up to (take your pick) .356 or .357 to use 200 grain bullets designed for .35 Remington. One could re-barrel a Ruger Mini-30 and have no other parts to change; the bolt and magazine would work as issued. One could do the same with an SKS or AK47 semi only variant and have a cruder version.

When I was much younger, I thought of a .25/.45ACP round. Neck down a .45 ACP case (probably have to use .308 Winchester cases and do substantial trimming and neck reaming) for use in a longer barreled and shoulder stocked version of a Government Model. The idea was based on the modified P-38 Walthers used in the "Man from U.N.C.L.E." television series. However, the whole design would entail manufacturing an 'any other weapon' under the 1934 National Firearms Act provisions and then not be very utile for much more than looking cool. Then again, a 50 grain FMJ .257 bullet at 2000 f/s would be a heck of a penetrating round.

So I don't see much need for new cartridges. But I would be interested in an M1 Carbine sized device chambered for 9mm Winchester Magnum - with a heavier bullet. For that matter, an M1 Carbine chambered for .40 S&W, 10mm or .45 ACP would be interesting.

I liked the idea of a 45 acp necked down to 40 but that's already done.

It's called a 400 Corbon.

Also there's a thread going in some other forum with the same question and I said a 9mm necked down to 30 caliber. That was done too.

i think OldManMontgomery pretty much covered it pretty good. with the calibers and cartridges available, it would be really hard to come up with something that either hasn't been tried before or something that works better than whats already available.

instead of trying to come up with something new, i would rather see some of the older, less popular and obselete cartridges make a comeback. l would like to see them in more modern firearms and different types than they were originally chambered for.

explosive cluster munition rounds ;)

How 'bout 7.7-06? (For a sporter Arisaka of course!) :p

Trez, that could have potential. i am sure that 7.7 Arisaka ammo isn't the easiest to find, and probably not cheap either.

30-06 brass necked up to a 7.7mm. custom reamer and posible bolt face modification. i see it as possible.

Why not just do what P.O. Ackley did and Improve older designs? Look at the .270 AI or .22-250 AI and how much he really improved them.

7.7 Jap brass can be made from .30-06 brass..
Just ream the chamber with a 06 reamer maybe? :confused: