Pellet efficiency

[Timmytree]

We often hear that heavier pellets are more efficient in PCPs and lighter ones better in springers. Is it time that theory was chucked out of the window? Personally I think it's more to do with pellet fit and hardness for a PCP and similar for a springer but add to that the balancing act between piston weight/preload and seal tightness.
I've just spent an hour in the barn firing pellets through the combro (still in one piece!) with the S200 and the Prosport, pellets used were my favourite AA Fields and Falcon Accuracy plus which PaulrBarnard, the previous owner of the S200 found most accurate.
You all know my PS has been intensively fiddled with, now I've had a little play with the S200 so testing was needed.
5 shots through the PS first to get things moving and then 12 over the chrono, discount 1 high and 1 low to leave a string of 10.
AA Fields.
776. 776. 774. 776. 775. 775. 776. 774. 776. 774. Gives me 11.2 ftlbs.

Falcon AP
819. 818. 822. 818. 818. 819. 819. 818. 819. 820. Gives me 10.9 ftlbs

Next the S200. Middle of the sweet spot at 130 bar.
AA Fields
783. 782. 782. 782. 783. 781. 784. 782. 784. 784. Gives me 11.4 ftlbs

Falcon AP
824. 821. 820. 819. 822. 820. 824. 821. 824. 823. Gives me 10.9 ftlbs.

So for me at least, the AA Fields are more efficient and give more power in both rifles. The S200 suggests the theory is right and the PS proves it is wrong!
I have to admit that the Falcon AP feel very nice in the PS, slightly better than AA Fields but nowhere near as accurate at anything over 40 yards. It looks like I might have to try a tin of the AA Field Express although I do begrudge the price of the damn things. Either that or I have to start having to play with piston weights again to try and make the Fields feel as nice during the shot cycle.

[gary martin]

good work Tim.
i am of the opinion that the theory that you are trying to prove/disprove is a general rule of thumb. in my EV2 the general rule heavy greater efficency holds true. In my pro sport its a little grey. i have not tried heavies through it, but with medium 8.44 & light 7.9 the difference is not worth splitting hairs over, just a matter of preference to which i believe gives the most consistant feel and performance in accuracy terms.
please let us know any more of your findings with greater/reduced piston mass.
Gary.

[Timmytree]

You're right Gary, it is a general rule of thumb but influenced by so many factors. Everyone quotes Bisley Magnums as producing the highest power in a PCP, imagine a pellet like the Bismag but made of the softer lead used in AA Fields! Maybe this just reinforces the fact that nothing can be taken for granted when testing pellets. I honestly expected the Falcon AP to be higher powered in the PS simply because the shot cycle felt so sweet and they are so light. Maybe what it does prove is that the AA Fields are amongst the most efficient pellets out there, a good BC at range but surprisingly quick out of the barrel too.
Regards
Tim

[gary martin]

Tim, the pellets i use in the PCP are soft lead. JSB Heavy 10.28 grain, my barrel loves them. i may give them a chrono run through the pro sport now you have got me thinking. my pro sport is running 11.2 ft/lbs with 8.4/7.9, if it gets close with the heavy 10.28 s you may be onto something. will let you know, i shall re-chrono with 7.9s and then with 10.28s on same day.
Gary.

[roadrunner]

The 7.9 jsb or AA express show a rise in energy of about .4 flb and feel really nice and are quick down range thats compared to AA fields in 4.51, my issue though is wind,at best where i shoot its a heady breeze unless i shoot a dusk which is not really the time for pellet/target practice so ive settled back on the fields as they cheat the wind better

[gary martin]

whilst testing with the PCP some time ago after changing to JSB Heavy 10.28g pellets, in the PCP the heavy pellets gave an extra 0.4 ft/lb of energy.
Timmy Tree had posted his theory about the perception of power output/pellet combo, i decided to give a test with the pro sport. the pro sport is in std form other than a polish of spring ends and proper grease applied to the internals.
pellets tested were JSB Express 7.9g and JSB Heavy 10.3g. a ten shot string was shot with each pellet after putting twenty pellets through first to settle the rifle in.
the express 7.9g gave an average velocity of 773.6 fps equating to 10.5 ft/lbs muzzle energy.
the heavies 10.3g gave an average of 673.9 fps equating to 10.39ft/lbs muzzle energy.
so the results in this instance live upto the general logic that spring piston give higher output using light pellets. but after a 0.4 ft/lb difference in the PCP to 0.11ft/lb in the piston rifle, maybe Tims idea that the piston mass may have an effect could be true. the std P/S has a heavy steel weight behind the piston, could a lighter one/heavier one effect efficiency?
the difference being so small did surprise me. the heavy would retain more energy down range and be less effected by side wind drift. the shot cycle was sweeter with the express. i did not test accuracy which of course is the greatest part of any equation, but the idea that timmy has, is certainly worth investigating further.
Gary.