Under lever does look nice. Out of my price point for this power plant but certainly a much better gun than a break barrel action. If I had spare change I would change to underlever for certain. 155 has same power plant as 135 break barrel. They have almost 10% more air volume in length of ram travel over the 125. Power rating is same but it must eek out a tad more. Likely the length of barrel is what held it back from true potential.It's a fixed barrel. Page 5 on manual shows how the breech is loaded. Barrel must be fixed under the breech.https://www.pyramydair.com/air-gunsresources/manuals/Torpedo_Series_Manual_GB.pdf
When I looked at them years ago I was afraid that loading port would be a problem. Have not heard of anyone having a problem. If I remember right the whole barrel moves back and forth inside the shroud to load it. If it's the same design I am thinking of it kinda defeats the ideal of a fixed barrel that makes under levers popular.