Another Small Frame Martini 40 Rimmed

[blackbahart]

had a 10 mm barrel and a loose SFM action already converted to CF
borrowed a 10 mm reamer from a friend fitted the barrel and chambered it ,went to load up some test loads and on the bench was a few 41 mag brass so run them through the sizing die and looked pretty neat .
Removed the barrel and run reamer to 1.3 inch and cut a relief for the rim
did some test loads using QL fires and extracts as expected ,
finished barrel 18.6 and tool blacked rifle
264093264094

[richhodg66]

So, do I understand correctly that this is chambered for a rimmed 10mm you make from .41 magnum brass? Sounds cool, I like the small Martinis.

If you had a 10mm barrel, seems like it could have been a .38-40 easily.

[hollywood63]

How did you get it sized down to the rim?

[blackbahart]

after sizing the case in the 10 mm sizing die there is a little belt above rim .I made a pilot that the sized case fits on and spin it in the lathe and just touch with a file as its only .010 to remove .Take almost no time at all but has to be done

[Pressman]

after sizing the case in the 10 mm sizing die there is a little belt above rim .I made a pilot that the sized case fits on and spin it in the lathe and just touch with a file as its only .010 to remove .Take almost no time at all but has to be done

Along the same line I made Herter's 401 brass from 41 mag by pushing the entire case into a 401 size die. The case is put on top of the shellholder and it will size all the way to the rim, use a brass rod to tap the case out of the die.

[blackbahart]

well I guess I have a Herter's 401 power mag,,,,, LOL,,,,,, .Didn't even dawn on me till Pressman's post /thank you for your information and now the name of it

I just put it together on a whim ,,,,as I had a barrel and an action and borrowed a 10mm reamer ,,,

[blackbahart]

Along the same line I made Herter's 401 brass from 41 mag by pushing the entire case into a 401 size die. The case is put on top of the shellholder and it will size all the way to the rim, use a brass rod to tap the case out of the die.

rounded up some star line brass and and followed you procedure and hot damm no need for the lathe ,,,,,thank you !
now the barrel does not like the hard cast ,barrel fouls up in about 10 rounds and starts to pattern ,dropped down to 1000 fps and still getting fouled and group opens up again

bullets are commercial hard cast with one lube grove and lubed and tried the semi wad and rnfp /going to try some ALOX on them and try again this week

[GhostHawk]

If your barrel is fouling I would look at powder choice first, lube second. A thin tumbled coat of either BLL or 45/45/10 should do it.

[john.k]

New barrel may be rough (ish) too.....might benefit from a polish with a fine abrasive.

[kenblacksmith]

I use HS-6 for my 10mm carry loads, extremely consistent velocity shot to shot.

[blackbahart]

problem solved =barrel no like cast! Hornady 180 gr XTP groups now and barrel clean no more build up (Green Mountain)