CR600 W.  CO2 - air strippers and muzzle breaks…

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

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

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

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

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

Straightmuzzle brakes worked well to the extent that I wonder how much of the airstripper effect was really attributable to the weight on the end of the barrelrather than the stripping effect. Then it got more complicated because as theshot count increased the breach and barrel temperature went from warm to coolto 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 highagain. I am too impatient to shoot brackets of pellets in slow motion. Thenthere is the minute of wobble of a very average shooter.

I am still impressed by the quality of this little Chinese rifle buttemperature change is a hard one.  I wassitting in a scrubby gully the other day. Sheltered from the wind and warm inthe sun. The little gun performed very well shooting off the knee and choppingoff blackberry stalks.  There is an extracost shooting CO2. Buying the 12 grams gas bottles and pellets according to mycalculations worked out about the same per shot as a .22LR if buying theammunition from the small bore club.