Quote Originally Posted by Hsing-ee View Post
If the piston seal is letting air past it, you can expect lower power, harsher recoil and poorer accuracy. I don't know if the 'dent' you mention is letting air past. If you put the piston in the cylinder without the spring, and hold your finger over the transfer port & press the piston forward with a dowel, you should get an idea of whether the piston seal is working well. Cuts on the lip of the piston seal can have a dramatic effect on power.

Maccari in the USA does a nice tuning kit for this rifle -

Usually takes a couple of weeks, but worth the wait. Price depends on exchange rate.

Spring and guides -

http://www.airrifleheadquarters.com/...488/552850.htm

Special piston washer

http://www.airrifleheadquarters.com/...485/945836.htm

good luck
Mr uk litehammer is well into Maccari for his air rifles which are top notch and he knows his stuff so it's got to be quality gear