The grandfather of all belted magnums. Every belted cartridge in existence — .300 Win Mag, 7mm Rem Mag, .458 Win Mag — traces its belt directly to the .300 H&H.
Type: Rifle
Introduced: 1925, United Kingdom
Parent case: .375 H&H Magnum
Standardization: SAAMI
Bullet diameter: 0.308" (7.82 mm)
Case length: 2.85" (72.39 mm)
Overall length: 3.6" (91.44 mm)
Max pressure: 54,000 PSI
Rim type: Belted
Primer: Large Rifle Magnum
Typical twist rate: 1:10
Muzzle velocity: 2700–3050 fps
Muzzle energy: 2430–3700 ft-lbs
Effective range: 600 yd
Common bullet weights: 150, 180, 200, 220 gr
Primary use: Hunting, Big Game
Production status: Active
Also known as: .300 Holland & Holland Magnum · .300 Super
History: Holland & Holland introduced it in 1925 as the 'Super .30.' Won the 1935 Wimbledon Cup — America's premier long-range rifle match — fired by American Ben Comfort in a Mauser action. This victory introduced American shooters to the belted magnum concept. Winchester commercialized it in 1925. The belt was originally a headspacing device for double rifles.
Notable firearms: Winchester Model 70, Weatherby Mark V, Custom Mausers
Similar cartridges: .300 Winchester Magnum, .300 Weatherby Magnum, .375 H&H Magnum