Quote Originally Posted by Hsing-ee View Post
In warm weather the aluminium expands to a far greater degree than steel and there are issues with the piston seal fit. Allegedly.
Certainly very "Allegedly".

The total expansion of the aluminium must be completely insignificant compared to the inevitable clearance between the piston and the cylinder, which the flexible seal takes up, and even manufacturing tolerances.

The reasons why a springer shoots differently when taken to the range after not having been used for a few days has more to do with lubrication than anything else. My TX shoots low at first, takes around 15 shots to get back to zero, until I realised I was constantly faffing around with the scope.

http://www.engineeringtoolbox.com/li...on-d_1379.html

Calculator shows that the circumference of the tube from 7C - 26C assuming a 3" start, increases to 3.0013 inches

Diameter at 7C = 0.954929658551372" = 24.255mm

At 26C = 0.955343461403411" = 24.266mm

0.011mm difference in diameter, that is, just over 1/100th of a mm

And that is ignoring the fact that the steel piston expands too, which it does, even if only half as much in circumference nominally, so the difference in FIT is even smaller.