https://www.neco.navy.mil/upload/N00164/N0016409RJN30000209RJN30_0002_att.pdf DETAIL SPECIFICATION CARTRIDGE, .300 WINCHESTER MAGNUM MATCH, MK 248 MOD 1 DODIC AB43, NSN 1305-01-568-7504 Revision A March 17, 2009] The 3 inches long MK 248 MOD 1 or alike ammunition is not offered commercially, since it exceeds SAAMI standards for overall length and maximum chamber pressure.