300 Winchester Magnum

Introduced in 1963, this soon became the most popular 30-caliber magnum chambering. It differs from earlier Winchester short magnums in having a slightly longer case. The stated reason for increased case length, combined with an unusually short neck, was to increase case capacity and therefore ballistic potential. While this had merit, performance difference between this and the wildcat 30-338 (338 Winchester Magnum necked to 30-caliber) is quite modest. Motivation for this design can best be understood by recognizing that Norma introduced the 308 Norma Magnum, a standard 30-caliber short magnum, in 1960. Likely, this preempted Winchester's development of a 30-caliber short magnum. Specifically, had Norma not introduced their version in 1960, Winchester would probably have offered a 30-caliber short magnum by about 1961. Almost certainly, that number would have been identical to the wildcat 30-338. Most agree that case neck length on a hunting cartridge should at least equal bullet diameter. Nevertheless, the 300 WM and several other successful Winchester numbers fail to meet this standard. Certainly, 300 WM popularity has not suffered in this regard. Despite the unusually long case body, this chambering is well adapted to standard-length bolt actions; however, bullets heavier than about 180 grains must be quite deeply seated and ballistic potential is, therefore, compromised. As with all 30-caliber magnum chamberings, the 300 Winchester Magnum is at its best for hunting larger species, such as elk and moose, at relatively long range. While recoil and muzzle blast are relatively heavy, most shooters willing to invest some time and effort in serious practice can handle and accurately shoot a typical hunting rifle chambered in 300 WM. As with all such chamberings, handloads with lighter bullets at minimum listed velocity can provide useful practice ammunition. Very important! A few production runs have been made with thicker brass, in this caliber. Therefore two sets of data is posted. One for the heavier brass with less volume and one for the lighter brass with more volume. The heavy brass weight is approximatily 270 gr and the light brass weight is approximatily 215 gr.
It is very important to use the right data for the brass that you have.