Sorry to bother you all with this trivial question(s)!
First can any there tell me what kind of max MV I could expect with this cartridge, shooting 73.3 grain FABRL bullets seated shallow in the case, protrusion only 0.2" into case, with a roll crimp in the canular in 16,18 and 20" BBLs? Also what powder and how much of it with chamber pressure of 40,000 PSI or less?
Second, do any of you know of an online internal balistics calculator where I might be able to answer this sort of question for myself?

Thank you for any help you can give, Sincerely, SFD.

You can buy software to get you in the ballpark but I've never seen anything online, or free, that will do it.

One of the software is called QuickLoad . Great stuff..

Your maximum muzzle velocity will be less than you can get with a similar weight 30 caliber bullet in the same case. If you are looking for an improvement in velocity or more penetration you are going to be disappointed.

The old carbine is a pistol case and not a large one at that. It simply can't hold enough powder to make much difference no matter the bore you push it through. The .22 versions approximate a .22 Hornet and they may be the best conversion.