I would personally never use themas I feel that they do offer the correct resistance in the barrel and so could allow the piston on a spring gun to impact hte end of the cylinder and so risk damage. I also have never seen a leaded barrel in an air rifle. They simply do not produce enough velocity to cause leading and at one time I was using 2 tins of pellets every week to ten days. Yep that 1,000 pellets every ten days through my .22 Feinwerbau Sport. Since I brought this air rifle in 1979-80 I have cleaned the barrel with a proper cleaningrod & brush twice and that was after getting soaked in the rain and I cleaned it to prevent rust and for no other reason.