So, here's a way we could really test this short-fat theory:
I have a drawing for a 30 cal, only 2.8" COL, with the same capacity as the 30-378. Put them in same-length barrel (from COL, not boltface, to be fair) and see what happens with velocity/accuracy.
Anybody got a short-action with a .9" boltface they want to donate to the cause?

Please post results as soon as you complete the test. Very interesting! roger

Well, I would love to, but I don't know of any easily-obtained action that will take the BMG case rim!
Obstacles!

BwanaBe,

You could just take a barrel, deep chamber it, install a threaded breech plug with integral striker assembly, mount the barrel in a fixture to hold it to a bench. To fire it use a linear hammer assembly mounted on the bench behind the barrel arranged to impact the striker assembly, and fire the whole thing remotely.

This would provide you with a proof of concept. After your testing was done you could then dispose of all the parts and contract a proper short action 50 BMG, if the results were to your liking.

Scott

You are so right. I was thinking rifle when I shoulda been thinking "mule." I've got more ideas than time and money, but I'll keep this one in queue.
For that matter I could put it in a beater stock as a screw-on single shot if it proved safe. Rig a hammer somehow.
DeHaas, where are you?

you may find this interesting:

http://www.roderuscustom.tzo.com/cgi-bin/ib3/ikonboard.cgi?s=3fe83fa703acffff;act=ST;f=3;t=418

338 version. Cant remember the case OAL exactly.

http://www.hunt101.com/showphoto.php?photo=24783&sort=7&thecat=500&password=

Seems like a simpler test would be to use the 408 CT, or 505 Gibbs case and shorten to duplicate the 308 Win. Just an idea...

Brent you're right, the bras would be cheaper, easier to chamber in standard pro gun, etc.
And anyway, one rifle wouldn't tell much. More about the builder than the cartridge.
Even an excellent cartridge like the 308 can be put together poorly, and I bet we could find a smith to amke a 30-30 sharpshooter.
Idea came from making up this short 30-Lap case, and just taking the idea to its extreme conclusion. I did draw this BMG-based case up, and it looks pretty funny. It's about twice as long in the body as it is thick at the base, whcih would be like a 1.3" 308 case necked down to 17 cal, COL of 1.9! (Hmm, he says....)

It would certainly be interesting if case capacities were the same and one took it to the extreme like that, in equal length barrels, MV and pressure should be pretty telling between the two, at least I'd think so.

If it were something I'd like to shoot, say in LR competition, I would try to compare the 260 and maybe a short fat CheyTac cased 6.5mm? I've read recently at BR Central that the 6.5 WSSM 40 deg Improved is doing well.

Alright, brent, here you go:
505 Gibbs, necked and cut to .264" and 1.2350", same length neck as 260R, 40*, .6390" at shoulder, should have same capacity. 408 case maybe a bit longer, b/c less capacity than Gibbs. But this Gibbs case would have a COL of 2" to meet the 2.8" 260!
Reamers are just a phone call away....