1907 Palma Cartridge for Camp Perry

[madsenshooter]

I'm still working on this! I got a quantity of new powder to try, IMR7383. It was the powder used, beginning in the late 60s for the M8 50cal spotting rifle on the 106mm recoiless rifle. The cartridge is smaller than the 50BMG and the powder was designed to burn at 38,000psi with a burn rate that appears to be between 4350 and 4831, about like RL19. It is bulkier than RL19, 40gr of it fills the Krag case up to the beginning of the shoulder and should give me the velocity I need to duplicate the Palma load at a pressure my alloy can take. I found that I could still easily chamber a round with the bullet sized .314, so I'm going to try comparing loads sized .311 vs those sized .314. First I'll try them out of my scoped cutoff (see cast shooter upgrade below), then later insure that my full length rifle, which has the same bore/groove dimensions, gets along with whichever load tops the comparison. I have the loads, mother nature is not cooperating, wants to rain on my parade everyday.

I found out why nothing would shoot worth a hoot in the post above. At the end of the previous range session I fired several loads that were overpressure for my alloy, the loads were blowing lead back on the caseneck, and I didn't clean the rifle afterwards, so the bore was pretty heavily leaded up. For those who think shooting jacketed will clean the lead out of the bore, it doesn't appear to me to be so.

[Mark Daiute]

Thanks, Bob, keep the reports coming.

[madsenshooter]

Mother nature left me out of the house for awhile today. I tried 40gr of 7383 behind the 203gr 311365 bullets sized .311 vs .314. Neither shot what I would call a group, more a pattern, with the .314 sized bullets shooting a tighter pattern around 3" without the two unexplained flyers the .311 sized bullets gave me. The muzzleblast from the 24" barrel sounded much different than what I had experienced with slow burning powders before. It was more of a thud vs a boom. The barrel didn't get very warm either, despite shooting over 20 shots. Both things are likely due to whichever additive it is that inhibits muzzle flash. No burning gases going down the barrel, not as much heat transfer. There were some unburned grains that using a magnum primer might rectify. It wasn't exceptionally dirty burning other than that, not as dirty as a caseful of 860. I noted that there was less blowback of lube onto the caseneck with the .314 sized bullets, so likely less gas escaping past the bullet. I also shot some with the same charge, but with a .311 sized bullet cast of a harder alloy that only weighed around 190gr. The first two of those were touching, I was adjusting the scope between the other shots rather that shooting a group, but it was pretty predictable moving right along with the scope adjustments. I don't know how far I'll have to drive to find some magnum primers, the powder surely needs them considering that it is lit with a 50BMG size primer in its normal application. That should tighten things up a tad. This is all just experimentation, I've held on to my RL19, I know what it'll do and unless something gets better with this powder the RL19 is likely what I'll use at Camp Perry.

[13Echo]

If you are getting blowback around your case necks you might try annealing them. It has worked for my blackpowder rifles but I haven't tried it with smokeless.

Jerry Liles

[13Echo]

Another thought. If you are trying larger diameter bullets you may need a larger diameter expander button so the bullet isn't effectively resized when it is inserted into a too small neck.

Jerry Liles

[madsenshooter]

Thanks for the thoughts Jerry. I'm partially neck sizing with a Lee collet die for the 7.5 Swiss with a washer between shellholder and the bottom of the die, the collet, so I size the neck down just enough to get .002 or .003 neck tension. No overworking the neck that way. The Swiss die only sizes about 2/3 of the neck, leaving the other 1/3 expanded to seal and center things. What lube gets out onto the caseneck doesn't go far. I had hoped this powder would light and burn more efficiently. I don't think I'll get the accuracy I'm after with something that doesn't completely burn like the RL19 does. Maybe some RL22. I can't say what I'll do, I might abandon the alloy that gives me the weight I want and go with the harder alloy that gives me better accuracy. Not just yet though.

[13Echo]

Hmmm. I was considering trying the Lee .303 collet die to resize case necks a bit larger than usual for cast bullets. Haven't got the die yet but do you think it might work with the Krag?

Jerry Liles

[Pentz]

I've been using the 30-06 collet die adjusted so that the neck just barely holds my .311 projectiles. Basically just a very tight slip fit. YMMV, because the major impediment is my eyesight since I'm shooting "issue" class.

[madsenshooter]

The .303 has a longer body and shorter neck, so it will partially size the neck of a Krag case, likely more of it than my K31 die does. There's a bit of adjustment, and if that's not enough, there's the washer. You don't have to squeeze the neck all the way down against the mandrel, just down as far as you want. http://www.jouster.com/forums/showth...brit-case-dims

[psteinmayer]

I'm using the .303 sizing die with the mandrel lowered enough to expand the neck slightly with out having to get the case too far into the die. Afterward, I use a tapered reamer to slightly taper the neck mouth to prevent shaving any lead off the bullet when seating. Works pretty good!