I built up my own short mag, using a Magnum M70 Winchester that was previously a slow .264 mag.
: After purchasing a Shilen .45 barrel, contoured heavy mag. and 22" long, I chambered it with a .450 Alaskan reamer, by hand.
; I turn off the rims of the .348 brass, cut a new extractor groove and neck up to .50m then back down to take a .45 bullet for fireforming, positioning the shoudle rin the correct place for headspacing.
: Another method is to open the .348 brass to .375. I then turn 500gr. cast bullet noses down to .375 and load with 45gr. H4895, seated out to engage the rifling heavily. These lubricated wadcutter shoot quite well to 100 meters, but best of all, are easy to shoot and fireform the brass out to the full size, perfectly. They make good offhand practise.
: This case, somewhat larger than the standard magnum case, results in a 2.1", bottle necked .458 with the same or slightly greater capacity than the .458Win.Mag. I use the same Reloader #7 loads listed for the .458WinMag in the Barnes manual with 350"X" and 400gr. Barnes Spitzer bullets. My accuracy is amazing, considering the 2X Leupold scope. These loads print on one another and hold to under 1" at 100 meters range.
; This short mag is a keeper.
: On the left is the old .450 Alaskan, the rimmed .348 necked up to .458 and blown out. This was designed by Harold Fuller of Alaska. My version, has the rim turned off and extractor groove cut. The new rim fits the mag bolt face of my Winchester M70 perfectly. Time on the lathe is less than 1 minute per case.
; The pictured bullets are 505gr. cast from a Lee mould. They shoot into 1" at 100 yards with a moderately light load at 2,000fps. This should make a good deep penetrating load for moose, elk and big bears. The 350 "X" at 2,400fps are flat enough shooting for an easy 300yards range, along with the 400gr. Spitzers at 2,300fps, neither are hot loads in my rifle.