Question about longer cases that headspace on mouth

[texassako]

I was wondering where headspacing on the case mouth starts to get problematic in a rifle cartridge. The reason I ask is there was a fleabay auction a while back for an inside neck reamer for something called a .41 Italian Special that included a set of .41 Mag dies. I did not bid, but it did make me stop and think. A quick check of measurements, and the Carcano case can be made into a rimless .41 Magnum. It could also be made longer. This article gave me an idea of what could be done with a longer case: http://www.lasc.us/Fryxell40-50SharpsContender.htm . If you cut the Carcano case at the shoulder(1.6"), the mouth could be the same diameter as the 10mm/.40 S&W, feed better, and use a Carcano sizing die with a 10mm/.40 S&W seat and crimp. The Carcano case tapers from .442 to .425 at the shoulder. I guess you could call it a 10mm Maximum. Am I crazy to be turning this idea over in my mind?

[DCM]

I like the idea, but that is just me.
The only down side I see is it will likely cost more to re-barrel than the rifle is worth.
Should be a nice 10mm thumper though.
Thinking some heavy LFNs with gas checks?

[texassako]

I like the idea, but that is just me.
The only down side I see is it will likely cost more to re-barrel than the rifle is worth.
Should be a nice 10mm thumper though.
Thinking some heavy LFNs with gas checks?

Green Mountain has .40 caliber raw blanks for $40-50 depending on length. The bubba donor rifles were all free, and all have cut down gain twist barrels that don't shoot. Definitely a thumper with a heavy bullet. The 1:16 twist should let me stay with a PB if I want to duplicate old .40 caliber BP ballistics of heavy and slow.