[AnAmericanMother]

nightdriver, you could be right, if it was 11 gr of Unique in a 6mm.

My standard load for .45 ACP is 7.5 gr Unique, and it's not a hot load for the .45. Without filler a 6mm load could have detonated.

I can't think of any of the IMRs that would have a small enough load to detonate. Even 4895 would fill it pretty full. That's my standard powder in the .303, it fills to just below the shoulder, and 4320 and 4350 fill up the whole case.

mameluke, why would I want to do that? ;-) I can always re-barrel. Lord knows I have enough extra parts around here . . . and besides, that would mean I'd have to buy another set of dies! Too many wacko calibers around here as it is (ask me about .455 Webley!)

[AnAmericanMother]

I found the reloading data for the 6mm Lee Navy in my old 1948 copy of Sharpe's "Complete Guide to Handloading". Mostly for old pistol-type powders that no longer are made, just two loads for IMR 4064 with no pressures given.

Unique IS a recommended load . . . with a 112 gr SP the data recommends between 10 and 14.1 grains. It's supposed to develop between 22,500 and 37,000 lbs pressure . . . that's not extreme at all. Sharpe did not consider the 112 gr bullet satisfactory, and did not like the rifle particularly. Apparently barrel erosion was severe (as in the .220 Swift).

So not underload or overload . . . just bad luck or bad metallurgy. What a shame.

[mamelukesabre]

The reason you would want to do that is so you DON'T HAVE TO REBARREL. You use the same barrel. The russian cartridge is slightly longer than the british one. So when you get the chamber enlarged to make room for the russian cartridge, the worn part of the barrel is removed.

TADA! just like having a new barrel.