: Win m70 (post-64)
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technical cartridge drawing
One of the two standard American big game cartridges. Introduced by Winchester in 1958. Most regard it as a commercialization of the 333 OKH Belted Magnum. Both are based on a 30-06 length blown out 375 H&H, one directly and necked down to .333", the other via the 458 Win Mag, itself a deshouldered, blown out 375 H&H, and then necked to .338".
The 338 WM represents Winchesters return to the .338" diameter bullet for heavy game hunting. (From 1902 until 1935 Win had its very popular one shot one kill 33 WCF, which it discontinued to allow for the introduction of the more powerful, but never very popular, 348 WCF - which itself was discontinued to make way for the 338 WM.)
The case capacity of 338 WM, full case, is 84.3 gr of water. This is larger than the 67.1 gr for the 338-06, or 76.3 for the 348 WCF; but still short of the 90.0 gr capacity of the 340 Weatherby, or the large 338s, eg, 119.5 for the 338 A-Square. Of note: the case capacity of the 338 WM might overstate the capabilities of the cartridge - with its short neck, powder capacity is eaten up by even moderate weight bullets.
As a heavy game cartridge it is viable on all North American game, under most circumstances. For lesser game, given the energy, becomes a meat waster. In Africa it has developed a reputation as a viable mid-size game cartridge.
The SAAMI maximum bullet diameter is listed as .3383", nominal diameter is .3380". SAAMI lists a recommended loading limit pressure of 54K CUP, with a maximum average of 57200 CUP.