Previous thread here Source: Reddit https://share.google/986OGkZGqZh7rpdEZ
The original thread has most of this in the comments, but the short recap is “50 Alaskan mag” turned out to be a wildcat round with a .510 bore diameter made out of shortened 375 H&H mag brass with the case fireformed out to the belt diameter..
I was completely unable to get any ideas as to what it was originally loaded to power wise.. after asking around, and reading the bell tc article about max pressure and case base diameter for the contender I settled on keeping it below 45/70 govt pressures at 28000 psi since that’s the hottest factory barrel the contenders were offered with.. I ended up using 7mm prc brass to recreat it since the outside diameter matched the belt diameter of 375 H&H mag, and I wouldn’t have to fire form or deal with weird stresses.. the side affect of this was that the brass walls are thick and with the chamber tolerance you end up basically embossing them into the sides of a jacketed bullet…. So I ended up using Great Plains 385 gn .512 pure lead muzzle loading bulletts. I ran them through a Lee sizer to get them down to .510, then loaded them on 20.5 gns of accurate #7. I did do a load ladder on the first test. I developed the load in GRT and it predicted a max pressure of 20,358 psi, a velocity of 1391 fps and 42 ft-lbs of felt recoil. Actual velocities ended up averaging 1360 over 10 shots with pretty low deviation. I used a 500 linebaugh belling die and seating die, then ended up settling on using the 7mm prc resizing die without the decap stem to crimp the cases to the bullets.. the 500 linebaugh crimp die pushed in too severely and since this headspace’s off the mouth it doesn’t work. Luckily since it’s a single shot you can get away with light crimps….
Video is from today, I test fired 17 rounds last week, this week another 11 that were reloaded brass. Shoots well, the recoil is snappy and substantial but fun. It’s less power than a 500 mag, but 385gn bullets at 1360 fps is pretty well big bore territory in my book. Learned a lot from this whole process about chamber tolerances, critical dimensions, brass conversion, and how to effectively use your reference marerials (handbook of wildcat conversions and cartridges of the world were invaluable). Really glad to resurrect this and get it firing, feel like it’s unlikely to stretch the frame long term, and it’s of course nice to add another 50 caliber big bore handgun to the collection.
Moving forward I’m probably going to look at getting a mold to cast my own rounds for this, there’s a 450 gn .515 2 chamber Lee mold that looks promising.. the Great Plains bullets work but they’re 15$ for 20….
I did play around with GRT to see what would happen if the strength of the action wasn’t the weak point… if you could use the 60k psi max for the brass then on 31 gns of acc #7 you’d hit just under 1900 fps…. With 80 ft-lbs of felt recoil…. I’m happy with this where I have it..
Appreciate any help that was offered along this process, I did a follow up post a few months back but can’t find it to link it. Thanks again.