The fundamentals of spring gun could be traced back to medieval. The power is kept in weights, slings and other strech based mechanisms. In this case the power for shot is created by the shooter himslef.
Now, lets talk about spring airsoft sniper rifle outer structure using some english terms, so that readers can adobt and use them for the furure. Will will cover main outer parts of the gun, adding some special features that you need to look for.
However, I would like to notice, that due to the available space here the outer structure will be a bit shallow, so future research on some specific things might be needed to cover everything.