Date: Apr 23 2020
The .450 Marlin was developed in 2000 as a joint effort between Marlin and Hornady Manufacturing. The goal was to produce a powerful load that would outperform traditional lowpressure .45-70 factory loads, while being housed in Marlin’s Model 1895 lever gun. For safety reasons, the new cartridge could not chamber in antique .45-caliber rifles. The .450 Marlin will push a 350-grain jacketed flatpoint near 2,100 fps from a 22-inch barrel, and due to its comparatively long, belted case, it will not chamber in .45-70 or .45-90 rifles.
Being a tapered straight case, the .450 Marlin requires a three-die set. For reliable chambering, cases should be full-length sized with the shell holder contacting (just slightly) the sizing die. To prevent buckling the case while seating bullets, case mouths should be flared approximately 1/20th inch to allow the bullet a “start” or begin seating.
Our test rifle features an 18 ½-inch ported barrel, which produced 1,826 fps with the 350-grain Hornady factory load, some 274 fps less than advertised speeds with 22-inch barrel. For duplicating factory loads, use Hodgdon H-4198. Results (shot to shot consistency and accuracy) with Vihtavuori N130 and Accurate AAC-2015 with the Hornady 350-grain FP were also good.
When loading the 325-grain FTX bullet, cases must be trimmed to 2.040 inch, then crimped into the cannelure for an overall cartridge length of 2.590 inches. If loaded cartridges exceed that length, most guns fail to feed reliably.
A Winchester Large Rifle primer was used to develop the accompanying data; however, Federal 210 and CCI 200 primers can be safely substituted. Large Rifle Magnum primers are not recommended as pressure increased substantially during testing and accuracy decreased.
A heavy crimp is suggested to keep bullets in place when subject to magazine spring pressure and recoil.