I don't know how to do two quotes....
Mr Frosty, the 357 Max is an example of answer to yoru question. There are Model 158's out there in 357 Max. the 357 barel can be rechambered to 35 Whelen or to 358 Winchester. The twist is slower than the upcoming 35 Whelen with 1-16 twist, but it does stabilize 250's. The 30-30 could be rechambered to 7.62X54R, sizing stems are available that allow for 308 diameter bullets, Lee offers them for their dies for $3.00
hvacman, I would be hardpressed to think that the Handi would not handle anything the Winchester '71 would take. The '71 is essecentially an 1886. The Accurate Arms manual #2 states that the 348 is rated to 40,000 CUP, that factory ammo ran at 29,000 PSI nad that their loads dont exceed that.
I think two things about it, the Handi is chambered in 12 guage 3 1/2" Magnum and in 10 guage. While the pressure ratings are different, anything that will handle a 2 ounce payload at 1300 fps will handle 1/4 of that at 2400 fps. I will rest may case on the fact that H&R built 35 Whelens on a cast frame. If the SB2 won't take the 348 case at factory levels I'll eat my hat. But do note that I qualify at pressures equal to factory pressure levels. Push it harder and you are in no mans land.
Accurate #2 shows the 348 pushing a 250 grainer at 2300 fps. The same manual shows 358 Winchester 250 grain loads at 2300 fps and 35 Whelen 250 grain loads at 2425 fps.
You would likely see 35 Whelen velocities from a 35/348 Ackley, but at what cost, especially considering that next year you can have a 35 Whelen? This ultimately is the problem with wildcats. Seldom can one find a wildcat cartridge that offers something a factory load doesn't. The 6mm-06 is one and the 25 Sooper (25-08) is another. Outside of those, what the factory offers is as good as can be found, and this is true of what most all factories are offering. A 250 grain bullet at 2400 fps is a 250 grain bullet at 2400 fps, don't matter if it is launched by a 35 Whelen or a 35/348, or a 358 Winchester. Substitute whatever bullet weights and velocities you care to, the end will always be the same. The 35 Whelen may not be a sexy or "OOH AAH" as a 35/348 would be, but the chronograph and the game wil be completely unimpressed. AI a 25-06. AI a 30-30. AI a 270 or 30-06 for that matter. In the end you will find that a 30-30 AI offers some real improvement, an AI 30-06 or 270 will likely just burn more powder to get you to the same place you were before the ream job, and why do a 7.62X54R when the Handi is offered in the 30-06 everyday???