Marty. This is about the coolest post ive read in quite some time. While you guys are light years ahead of my in physics and mechanical engineering, i would like to offer something that I have experienced with my diana 240. Now as most folks know, the tp of the 240 is on the rather large side of the tp spectrum. By expanding the tp, this reduces the air pressure to build enough energy to propel the pellet at a very high velocity. Makes sense to me. And if the tp were more restricted, air pressure would build up at a higher rate before travelling through the tp to push the pellet harder/fast down the barrel. With that said, i believe this rifle would fall under the ‘pop’ gun catergory of the cardews definition. In an effort to get this gun to shoot faster, i have tried heavier pellets thinking the pellet would allow more pressure to build, and light weight pellets to decrease the drag/friction during the travel down the barrel. Unfortunately neither has worked out as I had hoped. While not looking to acheive R1 velocities, i wanted something to stretch the distance range without too much of an arch in trajectory, and without maxing out the elevation of the rear sight. But this is what really has me stumped, in an effort to find a pellet to give longer range and higher velocity, God forbid me to say this, I ordered a Gamo Raptor gold pellets to try out. These pellets are about the lightest grain weight that I can find in .177. About 5 grains I believe. BUT,... even thiugh the skirt sizes are not as consistent as they shiuld be, they do fit very tight in the breech. When shot, i can see AND hear the pellet strike a bit faster than any other pellet I have tried. Im going to run a chrony test this afternoon with a variety of pellets, but I guess my question is, have the Gamo pellets become a ‘balance’ and/or the most efficient use of the power plant where the air pressures and pellet friction equal out?!?! Honestly, I was quite surprised how much better the ‘physical’ performance jumped with these over the H&N lightweight offereings. As an added bonus, the accuracy of the gamos wasnt to shabby. With a tight fit raptor pellet, they struck pretty much what I aimed at. Looser ones not so well. This isnt a gun i care to shoot groups with at long range (30 yards), but more as a tin can plinker for guests to shoot as an introductory into our hobby. But I also want them to be able to hit what they aim at and enjoy shooting without getting too frustrated with a pellet not getting to the target. Anyways, this is what I have experienced with a large TP’ed Diana 240. Thanks again for the great topic of discussion. Lots of good food for thought. tjk
Marty,At this point I have inside info about Hector's anti-bounce piston system, so I need to be careful about emphasizing any particular approach. I suggest you ask Hector directly. That is, unless it has been patented; in which case anyone can read about it, but not copy it commercially without prior agreement. If there are airguns on the market using the system - patented or not - you can talk about them openly.The only thing I will offer is that the opportunity for improving the TP is much more limited than for screwing it up . That the efficiency gains using some form of anti-bounce piston are more significant, in my opinion.
The TP in the rotating breech a BSA Super Star has a slight taper.
Hmmm - was the taper the result of the lack of recoil? The mystery thickens...
Quote from: MartyMcFly on May 07, 2021, 04:32:28 PMHmmm - was the taper the result of the lack of recoil? The mystery thickens... That air rifle looks heavy. The higher the ratio of rifle to piston weight, the less "recoil" is will have. Ditto, the lower the energy stored in the spring. A "full power" 11.4 FPE is hardly stressing anything very much...