Has anyone considered some of the Magnum Powders in the 10mm?
For instance, the .32H&R Magnum has a dimensional volume of .091 and the 10mm has a volume of .1
Published load data for the .32H&R with a 100gr (heaviest listed I found) calls for 10gr of 4227 at 19,300cup and 1060fps.
Just as an aside, that same load data, for that 100gr round called for 4.7gr of Longshot at 19,300cup and 1056fps
Why am I curious about this? I have half a pound of Longshot left, but 6 pounds of IMR 4227 (My Herrett loves it, but with my 10mm, I will not be loading and shooting the Herrett as much)
Since the .32H&R uses small pistol primers, I figured I would experiment first with Large pistol primers, if no signs of pressure, I would then try Magnum Pistol primers.
Pinsnscrews, It may be possible to get an ignition using the very slow powders in the 10mm but then again you may not and have a squib load. Those powders are usually used with bullets with a hard tight roll crimp, to allow the powder to fully ignite.
Powders like Winchester 296, H-110 can still leave you with a squip load. These slower powder require a full load of powder and possibly a compressed charge for maximum velocities. The 10mm case runs out of space and lacks a roll crimp and this is why it wouldn't be optimum with those powders.
Sorry
I had considered the crimp issue Shadow, however, the rounds I use IMR4227 in currently are not crimped, and a 10gr load measures to the bottom of the bullet with the 180gr Rainier PHP bullets I have on hand.
For testing, I will only be loading a single round at a time.
I wish I had a chronograph, so this little experiment may be delayed a while until I can get one. I also don't intend to shoot anything less than 200gr bullets with it.
Accurate #9 and Alliant Steel are about the slowest powders that develop decent velocity in 10mm.
Better bet would be find someone to trade you powder or buy your powder. That powder is just too slow to work well in 10mm.
But, as long as you are watching your target and ensuring your don't get a blocked bore, I really doubt you could get enough 4227 in there to have an over-pressure.