CR600 W.  CO2 - air strippers and muzzle breaks…

Some time ago I was browsing in Gun City and the little gas gun caught my eye. I bought it for $400. Not cheap but not too expensive.

For a Chinese gun it is very well made and the finish is pleasing and I enjoy handling it. It shot fairly well out of the box with just a barrel clean. That was ok for a while and then the amateur air gun mechanic urge got strong. The first change was to lengthen the pull by about 50 mms with a cedar butt plate. That was necessary because the rifle is very small. It comes with a silencer about 150 mms long. It works really well and improves accuracy with it screwed on. It works just as well with the end screwed off and all the baffles emptied out but then it is a megaphone and the rifle is loud. It also makes the barrel too long and a bit vulnerable because the barrel is long and thin.

 I opened the transfer port up to 4mms and enlarged the valve body size following Minty’s lead. That increased power somewhat because it now   buries a .22 pellet about a millimeter deeper into a piece of dry Pinus Radiata. Trigger adjustment is awkward because you have to dismantle the rifle to get at the adjustment screw. I overcame that by fixing a small brass wedge to the trigger guard that decreases the trigger travel. Overall the trigger is pretty good. The open sights are very good but obviously a scope is better.

On a wet day or two I made up a few muzzle breaks of various weights, six air strippers and three open ended cans. All were made on a wood lathe out of acetal plastic or out of aluminium tube and rod. A couple of the brakes are steel and quite heavy. The machining is tidy but not as precise as a proper metal lathe. 

Testing showed that the air strippers fashioned after the Hatsan or Rowen engineering models, with adjustable cones and elongated vent holes worked fairly well but not as well as my expectations. One fashioned out of aluminium bar was a complete disaster. No idea where the pellet went. The best two air strippers for accuracy were straight cans of 25 mm diameter and 15 mm bore with holes bored a right angles to the bore. The end of the can has a blunt washer affixed with 7mm exit hole for the pellet. Functional but not suave but I could feel a lot of gas coming out of the lateral holes. They certainly reduced group size at 25 yards. Then I had to make just one more stripper. This one is 60 mms long with vent holes at right angles to the axis and with a brass cone. That could be the best so far.

Straight muzzle brakes worked well to the extent that I wonder how much of the air stripper effect was really attributable to the weight on the end of the barrel rather than the stripping effect. Then it got more complicated because as the shot count increased the breach and barrel temperature went from warm to cool to very cold. The point of impact dropped about 15 millimetres over 25 yards. When the range master called a break the barrel warmed up and shots were high again. I am too impatient to shoot brackets of pellets in slow motion. Then there is the minute of wobble of a very average shooter.

I am still impressed by the quality of this little Chinese rifle but temperature change is a hard one.  I was sitting in a scrubby gully the other day. Sheltered from the wind and warm in the sun. The little gun performed very well shooting off the knee and chopping off blackberry stalks.  There is an extra cost shooting CO2. Buying the 12 grams gas bottles and pellets according to my calculations worked out about the same per shot as a .22LR if buying the ammunition from the small bore club.