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Shooting the M66 and M68
Posted by Al Frasca on Wednesday, 17 November 2010, at 2:41 p.m.
I finally developed a cartridge for my 1868 .50-70 Springfield Trapdoor. I found the first taper to begin at 2.26" measured from the base of the brass when fully inserted into the chamber. Using the Lyman 515141 cast lead bullet sized to .515" and seated to an overall length of 2.75" allows for approximately .020" of free travel before contacting the rifling.
I charged the brass with Goex FFG powder through a twenty-four inch, brass drop tube and filled the empty space above the powder with Dacron quilt filling. Furthermore, I annealed the first 1" of the brass to ensure a proper seal and to provide for future reloading.
I was absolutely astounded by the improvement at 100 yards. Before, when using a standard brass of 1.75" the impacts were random about a nine-inch circle. With the custom fitted rounds, the impacts closed into a two and one-half inch circle. This isn't minute of angle, but it's certainly a lot better than before. I can only surmize that before the free travel was such that it allowed scuffing of the bullet skirt that caused all manner of bullet dynamic problems while in flight.
Thank you for your assistance and confirmation that the early trapdoor had a long chamber.
John W. Ford
I have no idea how to post anything to a website. I do know how to email and that's about it. I should stress that it is extremely important to keep the brass behind the first taper. I have learned this first taper can vary from firearm to firearm. I found mine by using Sharps .50-90 brass and cut it down in stages until I could load an assembled cartridge with bullet in place. I found that when the brass was a tad too long, the trapdoor latch failed to drop into a locked position. It would drop part way on its own but not all the way. When I removed the loaded cartridge with bullet, I could see scuffing on the bullet end of the brass indicating the first taper. Once I trimmed the brass to remove all evidence of the scuffing on the brass caused by the first taper, the loaded cartridge allowed the trapdoor latch to close on its own. I trimmed an additional .015" off the brass and found it to be 2.25" in length from base to end. As I mentioned earlier, the entire overall cartridge length with loaded bullet to be 2.75" using the Lyman cast bullet #515141.
Al, if you feel any of my research and experimentation of value, please feel free to edit it for a website posting and post it. I have no idea where to do such a thing.
Sincerely, John W. Ford Vacaville, CA
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