600 OK... (Over Kill) is an entirely different animal from 600 Nitro Express. The only thing they have in common is .620 caliber. Naturally the 600 NE is for the double rifles, and the 600 OK for big bolt guns. 600 NE Rimmed and the 600 OK is a Belted Case.
We have had 3 such rifles here doing test work in past years, the last one was 2011 when we tested the .620 caliber CEB #13 Solids and Raptors. Two were CZs and honestly was not worth the weight in lead. Neither would feed nor function, one had to be single shot feed from the magazine, the other one had to be loaded with the cartridge slid under the bolt, and then put in the gun. Totally Useless POS.
The last one was a very well built rifle on a Granite Mt Action, and it indeed would feed and function properly.........
600 OK was developed in 2000 by Robert Garnick. It is designed and can supposedly handle 900 gr bullets at 2400 fps. It was not my mission to do any load data, but I used WW 760 for the most part from 150/WW 760 up to 170/WW 760 for the 900 gr CEB Solids and the 825 gr Raptors. I tested the 900 gr Solids from 1487 fps up to 2160 fps. The 825 Raptors from 1440 fps to 2201 fps.
I forget the exact weight of the Granite Mt Rifle, but it was at 13-14 lbs, with a 24 inch barrel.
In those days we were not really recoil shy, and I was used to shooting on average 10'000 rounds of Big Bore a year, several hundred each week doing load data, and bullet tech work. The last day shooting the 600 OK I had 22 rounds loaded up, and these happened to be the 2160-2200 fps loads. At the end of that test, I was very pleased I was finished I can tell you. Even I would not have wanted to shoot any at 2400.
At 1800-2000 fps it was not terribly punishing, it was like a big push, and of course there is a huge muzzle flip, or lift. You have to roll with it and let it do its thing, if you try hard to control the recoil and muzzle flip, it would get more punishing. And, recall, all the test work had to be done from the bench, there was no standing test work done, we had to have the closest precision possible to complete the mission, all from the bench.
We conducted other work with other bullets as well. I knew Robert at the time, and he sent several of his designs to be tested as well. If I were designing a bullet today for the 600s, I would go with something like a 700-750 gr Solid and a matching Raptor that would come in at 75 or so gr less. Run them at 2100 or so, and go about my business...........Although they are extremely effective at 1900-2000 fps, which is hi end velocity in 600 NE.
The same friend that sent his rifle down to me to be used in the test work also was a 600 NE fan, later used the bullets at great success for elephant and buffalo.
For me personally, rifles are way too big, too heavy, and I just would not carry that around. Yes, they are effective with the right design bullets, and yes, like everything else, totally useless with the wrong sort of bullet.
