......450 MONGO......


Glen Bolen <>

Below is a reponse to a post asking about the .450 Mongo.

This comes to us from Ben Sansing

About a year ago, I came up with a "wildcat" I called the .450 Mongo, which used expanded .444 marlin brass in my TC .45/.410 barrel as a sort of "Poor Man's .45-70". I announced this "great marvel" on the TC List, and people got excited about it. Some other folks have tried it, with varied rates of success. Apparently, TC has changed the chamber dimensions of their .45/.410 barrels over the years. In some barrels, the .444 brass works great. In other barrels, the chamber tapers too much or something and it won't accept .444 brass that's been expanded to .452" at the mouth. I kinda suspect they may have done this deliberately, to prevent people from using ".450 Mongo", since I'm sure I was not the first to come up with the idea of expanding and using .444 Marlin brass in .45/.410. I guess TC wants you to go buy a .45-70 barrel instead.

It should be a simple task to "open up" a TC .45/.410 chamber to accept the expanded .444 brass, and then you'd have a .45/.410/.450 Mongo! Older barrels (mine is one of the original octagon ones - and *may* have been rechambered outside the TC factory, I don't know (it has the screw-on choke, but is stamped ".45 Colt" with no mention of .410, though it chambers 3" .410s just fine)... anyway, older barrels *may* work "as-is".

Good luck, Ben


To Ben Sansing and all those interested in the 450 Mongo thread. As I previously reported, after preparing a number of 450 Mongo cartridges for fireforming, my friends and I found that none of them would chamber in any of the 3, 45 colt/410 barrels we have between us. I had my barrel shipped back to me from Arizona and I now know what the problem was and how to fix it. In flaring the cases I used a fairly steep tapered punch to start the expansion and a 45 acp expander to finish it. Because the expansion was tapered, I found that after seating a bullet in the case, a bulge in the case of several thousands was created immediately below the base of the bullet. the case measured .474-.475 around the body of the bullet (including case wall) but at the base of the bullet measured .480-.481. This bulge was enough to case the case to jam in the chamber and prevent full seating. I solved this problem by using a combination of dies (22/250, 45 Colt sizer and 45 ACP sizer) to resize the case WITH the bullet seated. The final step being to force the case (lubed, even though it was a carbide sizer) though the 45 ACP sizer. This reduced the outer dimension of the case to below .470 and solved the seating problem. As these cases are soley for the purpose of fireforming, I am not concerned waith accuracy. It would seem that the expansion of the case and bullet seating are critical to the successful preparation of cases for fireforming, Though I have been told by a gunsmith I spoke to that there have been changes in TC chamber dimension. A certain variation in chambers would be normal from the begining to end of the chambering process in any event. I think I may have found a better solution to the problem of case preparation and fireforming. As we all know, 410 shotshells may be fired in the 45/410 barrels. As a long time skeet shooter and shot shell reloader, It occured to me that the answer may be, for purposes of fireforming, to turn the 444 Marlin case into a brass shotshell. There would be absolutely no problem seating an unexpanded 444 Marlin case in the barrel. I seated a Winchester WWAA41 410 wad (for 2 1/2 inch AA cases) in the 444 Marlin and found it would seat perfectly. After checking a number of manuals and finding that all of them listed 10 grains of Unique as a safe load for 250gr bullets in the 45 colt (in a Contender), I primed a case charged it with 10 grains of Unique and seated the 410 wad. I then filled the case with number 9 shot to the top of the wad and weighed the shot. The shot weighed in at 190 grains. I then weighed one of the wads and found it to be 15 grains. The combination of wad and shot at 205 grains is substantially less then 250 grains, leading me to believe that 10 grains of Unique SHOULD be a safe load to fire. I then cut a thin cardboard overshot wad and sealed the case with a layer of 5 minute epoxy. Whether it will prove to be adequate to fuylly fieform the case is yet to be seen as I must first send them out to Arizona to be tested. I think this may prove to be the easiest way to form 450 Mongo cases and will report the results in a few weeks. Comments are welcome. --

Barry Miller

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