The 505 Gibbs is a remarkably well designed cartridge, especially so when considering that it was designed in 1911. George Gibbs initially called it the 505 Rimless Nitro Express, and it was intended to provide major-league dangerous-game stopping power in a bolt-action rifle. Until that time, several large, rimmed, Nitro Express cartridges had been doing the job in double rifles. This was quite a departure, and gave more hunters the opportunity to own a rifle truly capable of serious knock-down power.
The Gibbs is a relatively low-pressure cartridge, working at just under 40,000 psi. The massive case has a capacity of 178 grains (weight) of water. It drives a 525-grain bullet, with all of that delicious frontal area, at a comfortable 2300 fps. Striking energy is well over a half ton more than the quite popular (for Africa) 470 Nitro Express. A well-known advantage of the Gibbs over, say, the 500 Jeffery, is that it is an easy cartridge to extract from the chamber when a second or third shot is desired. The 505 Gibbs also has a notably longer neck than the 500 Jeffery, which makes for another advantage. The rebated rim (rim smaller than the diameter of the case) and higher pressure of the 500 Jeffery has been known to contribute to extraction problems, which can be a very bad thing.
Although the 505 Gibbs had been around for 25 years, it wasn't until Ernest Hemingway wrote about it in 1936 that it became famous. But, even after all of the fame Hemingway could throw at it, the bolt actions suitable for such a large cartridge were very limited and very expensive. That has changed in recent years, and now two quite reasonable current-production rifles chambered for the Gibbs are available; CZ's Safari Classic, and Montana Rifle Company's DGR. Ammunition is also available, but it isn't cheap. I find it best to load my own, and heartily prefer Hornady's 525-grain choices of the 0.505"-diameter DGX and DGS. Of the two, the expanding DGX is a better choice for most "plinking", unless you want to show off by shooting a solid through a 30-inch tree. Other makers supply bullets of up to 600 grains.
Some people ask, "How's the recoil?", and are surprised to learn that it isn't as bad as they might think. The low pressure helps to change the Mack truck-like blow of the 500 Jeffery into more of a hearty "push" with the 505 Gibbs.
There are cartridges that can put out more energy than the 505 Gibbs, including those for some of the larger double-rifles, as well as the 416 and 460 Weatherby. However, rounds such as the 458 Lott certainly fall short. And when it comes to the romance of the great African cartridges, hardly anything comes close. It may seem to be a stretch to some readers but, for the man wanting to have something a little different and absolutely capable, the 505 Gibbs makes more than a little sense for brown bear in heavy cover. Personally, I think the best thing about owning a 505 Gibbs rifle is being able to say you own a 505 Gibbs. Now, how cool is that?