Your Experience With Tough Alloys?
Posted: 14 Feb 2013 15:25
Finished up with the initial work with my R92 454 Casull using my 45 Colt bullet, the TLC454-290-RF. This bullet is sized to .452" and seated to an OAL of 1.800" for a perfect fit in the Casull's chamber. The bullet is cast from a 95/5, wheel weights/tin alloy mix, I do add 1 ounce (volume) of #8 shot to 10 pounds of the alloy and then water quench the bullets for a BHN of 21.
I've always considered this mix and BHN to be capable of surviving chamber pressures of 48.0 KPSI and today's shooting reinforced that thinking. My 34.0-grain load of Lil-Gun was producing 2155 FPS at 48.0 KPSI. There was no evidence of leading at this scoped sighted rifle was drilling the same hole at 50-yards. On to the next step of developing the potential of this rifle.
In another post I mentioned the work I was doing on a 454 Casull bullet specific for use in the R92. After looking at what the chamber needs to ensure a good fit (throat, leade, and step via chamber cast), I want a projectile that will maximize these features at the maximum pressure with a full case of propellant form an appropriate powder. The first part of the previous statement, I believe, has been met with my TLC452-330-RF, 330-grain, Round Flat Nose Bullet.
When loading to the max of any given cartridge, a typical target pressure is 15% max in order that the extreme spread of pressure deviations are contained within the max. In the case of the 454 Casull's 65.0 KPSI, the actual target nominal pressure would be about 57.0 KPSI.
My experience has taught me that a full case of powder makes an accurate cartridge. I personally like seeing a case density between 95% to 105%. With cast bullets and their lube, I find it tough to keep a consistent seating OAL between the bullet seating stage and the crimp stage when 105% is exceeded.
Using Quick Load to crunch the 57.0 KPSI NMP/65.0 KPSI PMAX consideration limiting the powder density to 105%, it spit out one of my favorite short case powders as offering the best potential. It seems that 31.5-grain charge of Lil' Gun will be sitting at 57.2 KPSI while pushing the 330-grain bullet at 1960 FPS!
Now, it all boils down to mixing and treating an alloy that can survive another 9.000 PSI. I have several thousand pounds of lino/monotype but little experience in working with it. Always wanted to get to it but really did not need to so now is the time. Also the only oven I have for heat treating the alloys is one that would create a lot of heat for me if I was caught using it for this endeavour.
Of course, I have all the cast bullet references and well versed in sources like LASC to include TMT's Alloy Calculator software but would like to hear what your experiences are. My thoughts are I will need a BHN in the neighborhood of 30 to 32 for the pressure and would like to get there with lino/monotype vs. heat treating. Any thoughts? Your experience would be appreciated.
I've always considered this mix and BHN to be capable of surviving chamber pressures of 48.0 KPSI and today's shooting reinforced that thinking. My 34.0-grain load of Lil-Gun was producing 2155 FPS at 48.0 KPSI. There was no evidence of leading at this scoped sighted rifle was drilling the same hole at 50-yards. On to the next step of developing the potential of this rifle.
In another post I mentioned the work I was doing on a 454 Casull bullet specific for use in the R92. After looking at what the chamber needs to ensure a good fit (throat, leade, and step via chamber cast), I want a projectile that will maximize these features at the maximum pressure with a full case of propellant form an appropriate powder. The first part of the previous statement, I believe, has been met with my TLC452-330-RF, 330-grain, Round Flat Nose Bullet.
When loading to the max of any given cartridge, a typical target pressure is 15% max in order that the extreme spread of pressure deviations are contained within the max. In the case of the 454 Casull's 65.0 KPSI, the actual target nominal pressure would be about 57.0 KPSI.
My experience has taught me that a full case of powder makes an accurate cartridge. I personally like seeing a case density between 95% to 105%. With cast bullets and their lube, I find it tough to keep a consistent seating OAL between the bullet seating stage and the crimp stage when 105% is exceeded.
Using Quick Load to crunch the 57.0 KPSI NMP/65.0 KPSI PMAX consideration limiting the powder density to 105%, it spit out one of my favorite short case powders as offering the best potential. It seems that 31.5-grain charge of Lil' Gun will be sitting at 57.2 KPSI while pushing the 330-grain bullet at 1960 FPS!
Now, it all boils down to mixing and treating an alloy that can survive another 9.000 PSI. I have several thousand pounds of lino/monotype but little experience in working with it. Always wanted to get to it but really did not need to so now is the time. Also the only oven I have for heat treating the alloys is one that would create a lot of heat for me if I was caught using it for this endeavour.
Of course, I have all the cast bullet references and well versed in sources like LASC to include TMT's Alloy Calculator software but would like to hear what your experiences are. My thoughts are I will need a BHN in the neighborhood of 30 to 32 for the pressure and would like to get there with lino/monotype vs. heat treating. Any thoughts? Your experience would be appreciated.