I made up some loads to test in my Puma 44mag. I had some BTB 250 wfngc's and some Lazer Cast 240 lswc's. The 250's were .432 and the 240's say they are .431 but they measure about .432.

The load for the 250's was 24grns of H110 for about 1700 fps. I had two loads for the 240. One was 20grns of H110 for around 1500 fps and the other was 10.5 grns of Unique that ran about 1300 fps.

The loads using unique were key holing. This was very puzzling. The bore is a bit oversize and the rifling is shallow but I have shot a bunch of 200 grn Hornady XTP's (.430) through it at about the same velocity and they didn't keyhole. Any ideas?

Your Key hole problems are most likely due to a slow rate of twist in your Rossi Puma. I don't know what rate of twist they use but since you say you receive better results using 200 grain bullets lets me believe this is your problem. I use 23.5 grains of H-110 + 240 grain Hornaty XTP in my Ruger 77/.44 Mag. Bolt Action and have no problems with "Key Holes". This is due to the fact that Ruger used a faster rate-of-twist, in their barrels made for the .44 Magnum. Do you receive Key Holes using 240 grain factory ammo?

I would agree with you and that is what is perplexing me. According to the Catalog 44mag Puma's have a 1-30 twist. The 250's from BTB's shoot just fine. The two 240 loads I made are using the same bullet just driven at differnent velocities. The faster shoots fine while the slower keyholes. Riddle me that. ;)

Just a stab here as im still learning the wonders of cast. With the lighter load and the bore on your rifle, the lighter charge may not be enough to obturate the boolet base enough to get a good hold on the rifling causing them to keyhole.

I would agree with you and that is what is perplexing me. According to the Catalog 44mag Puma's have a 1-30 twist. The 250's from BTB's shoot just fine. The two 240 loads I made are using the same bullet just driven at differnent velocities. The faster shoots fine while the slower keyholes. Riddle me that. ;)

You might try using another powder other than H-110 or Unique. Something like IMR-4227 or similar powder with the same burning rate. I have a Rossi Puma in .44-40 and never had the problem of key-holes with any of my loads. I am sure they used the same rate-of-twist as in your .44 Magnum Rossi. Again, it sounds like your velocities, for the 240 grain Hornady XTP's are a bit too slow, and you might consider just using 200 grain XTP bullets for your "jacketed" loads. Hope this helps. :)

I would agree with you and that is what is perplexing me. According to the Catalog 44mag Puma's have a 1-30 twist. The 250's from BTB's shoot just fine. The two 240 loads I made are using the same bullet just driven at differnent velocities. The faster shoots fine while the slower keyholes. Riddle me that. ;)

That is what you would expect if the twist was marginally able to stabilize a bullet. The faster velocity would result in the bullet spinning more rpms and being more stable.

We use bullet weight when we talk about whether a twist will stabilize a certain bullet or not but it is really the length, not the weight that makes the difference. Obviously heavier bullets are usually longer but not necessarily in this case where there is only a ten grain difference.

Rod,

That was my thought.

Davers,

The 240grn bullets are Oregon Trails Lazer Cast lswc's. They are sized .431.


I guess I will just "have" to shoot hi velocity loads. :D

Go here and look at the data for the Laser Cast bullets and Unique powder. This gentlemen compiled this data while writing the Laser Cast reloading manual.
http://www.gmdr.com/lever/lowveldata.htm