Big Bore Compendium – .505 Gibbs

01The 505 Gibbs was designed by George Gibbs of London to provide big bore stopping power in a Mauser style bolt-action rifle. It is considered the king of the classic big bore cartridges and is gigantic in its dimensions. The actions that will properly handle the cartridge are gigantic as well, and the price tag for a rifle in this caliber has a Texas-sized price tag.

The 505 Gibbs has an overall length of 3.85 inches, making it unsuitable for all but a few magnum actions. Those considering a .505 Gibbs would do well to use an action that has a bolt body diameter of more than 0.700″ (which is standard in the model 70/model 98/ CZ550) because after the bolt face is opened up for the Gibbs 0.640″ rim, there is just a very thin sliver of metal left on the bolt opposite the extractor. Starting with a larger diameter bolt at the outset, such as the 0.750″ bolt found in Granite Mountain Arms magnum mauser actions, adds to the durability of the rifle. Another alternative is a P14 Enfield action since the P14 bolt has a left lug that extends beyond the boltface, providing extra metal opposite the extractor which can accommodate the Gibbs very large rim.

At first glance, the .505 Gibbs original factory ballistics of a 525 grain bullet at 2300 f.p.s. do not appear to offer much more power than a .458 Winchester Magnum. After all, it is just 25 more grains of bullet weight and 150 feet per second more velocity. However, the ballistics can be improved by stepping up to a 600 grain bullet at 2400 feet per second. Of course the Gibbs also has the advantage of greater bullet diameter than the .458.

At present, factory 505 Gibbs rifles are available from Reimer Johannsen (, Hartmann & Weiss and Heym ( CZ has announced that it will introduce a .505 Gibbs rifle at the Shot Show in 2005. Alternatively, master gunsmith Ryan Breeding of Palmdale, California ( offers a beautiful 5 shot .505 Gibbs bolt rifle, and custom gunmaker Joe Smithson of Provo, Utah turns out perfection in a 505 Gibbs on a Granite Mountain Arms action. Karl-Heinz Ritterbusch ( offers top quality .505 rifles as well.

Most 505 Gibbs rifles made today are custom built by individual gunsmiths today with about a 1-2 year lead-time. It is a magnificent classic cartridge with wonderful stopping power. For those who wish to maximize the punch of a hunting rifle, even more potent combinations are discussed further below. Recoil from the .505 Gibbs is significant due to the heavy powder charges it uses. To control recoil, .505 Gibbs rifles should weigh 11 pounds or more.

On cape buffalo, the .505 Gibbs has been observed to have significantly more shock effect than anything in the .458 class, due to its greater bullet diameter. Performance on game of the .500 Jeffery, .500 AHR, and 500 A-Square will be essentially the same as the .505 Gibbs. The advantage of the .505 Gibbs is its classic design and standard dimensions without a rebated rim. The disadvantages include need for a very expensive magnum mauser action, periodic shortages of brass, sometimes inconsistent brass quality, and a relatively narrow selection of bullets for the .505″ diameter bore. If you want a 505 Gibbs, there is no inexpensive route. But a well-made 505 Gibbs is a rifle is a genuine treasure.

Example loads:

Cartridge Powder Primer Bullet Velocity Notes
505 Gibbs 120.0 grains Reloader 15 F215 600 grain FMJ 2325 f.p.s. 4 grains Dacron filler between bullet and powder
505 Gibbs 136.0 grains Reloader 22 525 grain A-Square 2328 f.p.s. .Use of a slower burning powder such as IMR7828 or RL22 permits fillers to be avoided.