There was a thread started by Doc Rocket back in 2012 about modifying brass to make handgun shotshells for .45 Colts and .44 Magnums. This is done by modifying other brass to fit the chambers. The thread initially dealt with making these shotshells for a .45 Colt. Later in the discussion, it was said that for a .44 Magnum, they could be done by modifying a .445 Supermag case. The supermag case does not need to be shortened, but the forward .30" or so does need to be sized down to fit the chamber throats. The overall case length is fine for the chamber, thereby using the most room for a large shot load. It was said that these supermag case ends can be sized down properly by using a .40 cal/10 mm sizing die. The outside diameter of a .445 SM case is the same as a .44 Mag case, .456". The throats on my .44 are exactly .430". The outside specs for a .40 cal case is .423", so this should fit just right in my chamber throats. Now, my problem is both times I have tried to run a piece of .445 SM brass into my .40 sizing die, I have crushed the case. Anyone have any ideas how I can downsize this to fit a .430" throat? I only need about .30" of the case end downsized. I have tried unsuccessfully to contact Doc Rocket about this problem. He and others have done it, so I know there is a way.
try starting your necking with a 41 mag sizer. if using a carbide still lube the snot out of the case. lettuse know how it turns out.
When resizing cases, I've found that it helps to go by intermediate steps, lubing the case well (I use a wax, the name of which I can't remember) and going slowly, inserting the case a little bit, backing it out, turning it 90 degrees, inserting it again, backing it out, turning it again, etc. It's a slow process, but it works for me. I'm sizing .30-30 cases down to .219 Zipper, so you'll see why I'm doing it in steps. I don't know what you could use for an intermediate step, but 0.026 in one step is asking a lot.
try starting your necking with a 41 mag sizer. if using a carbide still lube the snot out of the case. lettuse know how it turns out.
Best option, think 41 mag is .432
Before there was a 445 Supermag I used cut to cylinder length 30-40 Krag brass with rims thinned & reduced in diameter. After fireforming a Lyman 41 mag carbide die has always worked for me. Nothing else needed. My cylinder throats measure .432".
Just checked a few of these & the reduced portion of the case measures between .427 & .430". Thinking the carbide insert is tapered a bit, so maybe just push the case in a tiny bit more to fit your cylinder? There's not enough threads in the press to properly adjust the die for full ram movement, so it's all done by feel. I usually insert the shortened .410 wads before sizing, but can still sneak them in afterward. This sure isn't precision reloading, so if the "neck" is a few thou longer it doesn't matter.
Thanks to all for the replies! Sounds like logical advice, going from .456" down to .434", then down to .423". I happen to know of a local fellow who had some .41 Mag dies for sale a while back. I will call him and see if he still has them. If so, I'll then have an excuse, er...I mean, reason to get a .41 since I will have the dies to load for it, right? Sounds logical to me.... Now, if I can get my wife to buy that reasoning! :-) Enjoy the day!
OK, situation update: I bought the set of .41 Mag dies. Resized a .445 Supermagnum case in the .41 sizing die (well lubed) down about .30". No problem doing so. Then changed to the .40 cal/10mm sizing die, relubed the case, and completed the sizing down to where I did before. The case fits perfectly in my .44 Magnum chambers. Thanks for the advice to all! It worked like a charm.