Air Stripper

I have a Hatsan 22 cal air stripper. It has a bronze cone in it with a set screw holding it in place, do I leave the cone where it is, or should I try to adjust it closer to bore of the barrel?
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You can adjust the cone to see where the optimal placement is in term of best accuracy. I would start with the cone on either end of it's range and then shoot three or more groups with it in that placement. Move it a bit towards the other end of the range, shoot three or more groups and continue until it's at the other end of its range. Average out the size of the groups from the different cone positions and you'll know where the best placement for the cone is on your rifle. 

I would also then shoot some groups without the stripper. May be that it's more accurate with out it!! Also, clean the barrel before shooting each set of groups. And if you really want to get picky, size your pellets so that you are shooting the same head diameter pellets in your testing. This may be obvious, but do the testing indoors. 

Chas