So I started down this path a couple years ago, but not so far as to fall down the rabbit hole. Using Longshot and loading to 1.395" OAL, I was able to get over 1400 fps. with a 180 gr. HAP, and no pressure signs. That's 100 fps faster than the top end book loads got me at standard OAL from the same 6.5" barrel.

I would not be uncomfortable going higher with this one.

I think the heavier bullets are where the long-loaded rounds would really shine. Maybe I'll tinker around with some over the winter.

But in the end I decided this is never going to overtake the traditional magnum revolver cartridges. At least not without going way over SAAMI max pressure. If I want more power, I have other guns in the same platform that are chambered in more powerful cartridges and have the same capacity.

And maybe it's a funny thing to get hung up on, but I never found an ammo box that works well for these longer rounds. They are too long to fit in a typical 10mm/.45ACP box, and too fat to fit in the slots in a .357 box. And they just rattle around too much in a .41/.44/.45Colt box. Silly thing to get hung up over, I know.

Sorry for resurrecting an old thread, but it was interesting to me.  I shoot 10mm through a Blackhawk, and I can't see where rimmed brass would make any difference in a single-action revolver vs. the typical rimless brass.  But it seems interesting nonetheless.

So I started messing around a little. I found that chopping a .30-30 case to the correct length did indeed produce something of the correct diameter that would drop into my cylinder with no issue.  I find the .30-30 also has a rim diameter very close to the .45 Colt, which means they will all fit in the cylinder without interfering with eachother.  (yes, I chopped 6 of these and tried it out). 

The one real issue is that cutting down .30-30 rifle cases results in a rimmed pistol case with a case wall thickness at the neck of around .025" thick.  Regular 10mm brass is only around .010" thick at the neck.  Attempting to bell the neck and seat a bullet did not turn out very well.  It will be necessary to turn the case necks.

I don't have a neck turning tool for my RCBS trimmer, but I've been looking for an excuse for a while now so I went ahead and ordered one.  Unfortunately this will only let me trim the OD of the neck. RCBS makes an ID boring tool, but they are caliber-specific, and only go up to as large a .375".  So I'll have to see what it looks like if I turn the OD of the neck. 

More to come...