From the link below:
338 Allen Xpress
338 Lapua Magnum parent case, fireformed to Allen Magnum shoulder and body configuration.
200 gr. (3350 to 3450 fps in 27-30” barrels) to 300 gr. SMK or ULD RBBT (2850 to 2950 fps in 27-30” barrels)
Designed for heavy game out to long range.
Appropriate powders: H4831, Rl-22, Rl-25, H-1000, Ramshot Magnum, Retumbo
Allen Mag Shooters Group