Different size cylinders and power.

[Muskett]

This is getting beyond my knowledge, but anyhow..
Marconni of USA FWB fame has two spring set for the Sport: Old School and New. Basically the short and long springs have the same power when compressed; latent power. Everything else is to do with the chamber and how all that energy is transferred by air pressure to the pellet and as that pellet travels along the barrel until free. And still leave an air cushion for the piston to come to stop with out slamming into the front of the chamber.

I had great success with Theobens once they refined their designs. All shot very well. Non had any power or consistency issues. My Fenman hasn't missed a beat in 20 years.

[Hsing-ee]

This is getting beyond my knowledge, but anyhow..
Marconni of USA FWB fame has two spring set for the Sport: Old School and New. Basically the short and long springs have the same power when compressed; latent power. Everything else is to do with the chamber and how all that energy is transferred by air pressure to the pellet and as that pellet travels along the barrel until free. And still leave an air cushion for the piston to come to stop with out slamming into the front of the chamber.

I had great success with Theobens once they refined their designs. All shot very well. Non had any power or consistency issues. My Fenman hasn't missed a beat in 20 years.

I tried a short Maccari spring in my FWB Sport, it was alot easier to fit but I think it shot nicer with the longer spring. The Theobens have triggers which are poor in action considering the cost of the rifle, I can only think people are buying them because of they are unusual and have rarity status. How many HFT or old school FT competitions did they win? or even come in the prize list. Probably have the same power/accuracy performance as a tweaked BSA Meteor, with half the style.