by B.B. Pelletier
Today, I’ll test the velocity of the Gamo Extreme CO2. Remember, this is a .22 caliber repeater, and Gamo lists it as a 700 f.p.s. gun. Of course, that velocity represents the fastest they expect it to go, and it will only do that with lightweight pellets.
I installed the 88-gram CO2 cartridge with no problem except the room to grasp the cartridge is small. So, I found myself turning it in small increments. Naturally I put three drops of Crosman Pellgunoil on the spot where the cartridge would bear when screwed in, so the oil would be blown all around the inside of the valve.
To load the 10-shot clip, you first pull the sliding forearm all the way back. Then, a second lever on the right side of the receiver is retracted. The clip can then be picked out of its notch in the right side of the receiver.
The sliding forearm operates this slide-action repeater, or “pump gun,” to use the slang term. The only other gun I have to compare this one to is the .22-caliber Shark from Argentina. That rifle is relatively hard to pump, while this one is quite easy by comparison. You cannot hold the trigger down and work the action, because the mechanism is not designed to work that way. But it’s still a very fast repeater.
Crosman Premiers weigh 14.3 grains in .22 caliber, which is a medium weight for a .22. In the Extreme CO2, they averaged 630 f.p.s. with a high of 650 and a low of 599. The average speed produces a muzzle energy of 12.61 foot-pounds.
The trigger-pull is two-stage, but the start of stage two is quite vague. You really have to feel for the second-stage pause. The one I’m testing varies between 5 lbs., 2 oz., and 5 lbs., 9 oz.
RWS Hobbys, at 11.9 grains, are the lightest lead pellets available, so I try to use them for the velocity testing of most airguns. In the Extreme CO2 they averaged 655 f.p.s. with a spread from 646 to 667. At the average velocity, they’re churning out 11.34 foot-pounds. We know from experience that light pellets don’t usually produce as much energy as heavier pellets in gas and pneumatic guns. So, I’ll also shoot a heavyweight pellet at the end of this test to demonstrate that pattern.
Gamo Hunter pellets weigh 15.3 grains and are a pure lead pellet, as opposed to the hard alloy Crosman Premier. They averaged 626 f.p.s. in the Extreme CO2 and the spread went from 616 up to 634. At the average speed, they’re cranking out 13.32 foot-pounds at the muzzle.
Super heavyweight pellets
For this test I used some obsolete RWS Ultra Mags I had on hand. They weigh 28 grains and just barely fit in the clip. I could feel them bumping around as I worked the sliding forearm. They averaged 500 f.p.s., with a large spread from 464 to 513. The average speed gives an energy of 15.55 foot-pounds at the muzzle. So, the relationship of weight to efficiency in gas guns has been demonstrated. Not velocity, you understand, just power.
Three times during testing the forearm came off the gun when I slid it forward. I think the cause was that I had one of the dismounting buttons depressed with my hand, but they’re in a natural place for my hands to hold, so I have to guard against doing that.
The bottom line at this point is that the rifle has demonstrated the advertised power. Yes, it didn’t quite get to 700 f.p.s., but with non-lead pellets it would so so quite easily. I know there are those who are watching to see how this rifle stacks up against the Hammerli 850 AirMagnum, so this is your first indication.