Standardized by Remington in 1955, the 44 Rem Mag uses a lengthened version of the 44 Special case. It was originally loaded to extremely high pressure. As such, performance was impressive. Factory loads from Winchester, Remington, and Federal all launched 240-grain bullets faster than 1500 fps from typical revolvers with six-inch barrels. Elmer Keith was not alone but he was the most noted gun-writer involved in hotrodding big-bore revolver cartridges in the 1940s. His favorite soon became the 44 Special, which he loaded with cast bullets of his design using Hercules 2400 to achieve between about 1100 fps and 1200 fps in large-frame Smith & Wesson revolvers and Colt Single Action revolvers, respectively. He widely publicized his work in various gun magazines, suggesting loads and explaining what such high-performance 44 Special loads could do. Keith was never happy with what Remington did with a chambering he envisioned as a means of duplicating his high-performance 44 Special loads. He always advocated for standardized loads generating far less pressure and launching bullets a few-hundred-fps slower. Keith believed more shooters would be able to handle the recoil of such loads and that such loads did everything the hotter 44 Magnum loads did in most situations. He was right. After many decades, we now find SAAMI pressure standards for the 44 Magnum closer to what Keith would have specified with performance just about where he would have put it; e.g., 240-grain bullets at about 1300 fps. As such, the 44 Magnum followed the same path the 357 Magnum had, as time moved forward and more and more manufacturers chambered the round in more and more guns. Some of those might well have been inadequate to handle the 65,000-psi that H. P. White Laboratories measured for early factory 44 Magnum loads in testing paid for by Keith to prove his point about the original loads far exceeding what he considered necessary and prudent. With Alliant 300-MP, it should be possible to get higher velocity than H110/W296 will give but loading data is extremely limited. The other top performer in the 44 Magnum is Lil’Gun but Freedom Arms reports extremely rapid forcing cone damage with the use of this propellant. All ball-type propellants are hard on magnum revolvers but Lil’Gun seems to be the worst. Jacketed bullets are also harder on a revolver than cast bullets are. Keith warned me I would soon wear out the forcing cone on my Ruger Super Blackhawk if I insisted on shooting my preferred load with jacketed bullets and H110/W296. He knew what he was talking about. By the time I attained the pinnacle of my abilities to shoot the gun fast and accurately, the forcing cone was so eroded I had to set the barrel back two full threads to remove all the damaged material when cutting a new forcing cone. If you care about barrel life in any magnum-class revolver avoid ball-type propellants and jacketed bullets. Elmer would smile! As with any revolver round, best practice is to apply a roll-crimp after seating the bullet. This helps to lock the bullet in place against chambering forces that might otherwise drive it into the case. I cannot too-strongly recommend getting a second seating-and-crimping die so you can have one adjusted to only seat the bullet and the second adjusted to only crimp the case mouth. Generally, attempting to do both operations in one step is a recipe for damaged and destroyed cases.