How much air?

[angrybear]

yeah there's a big difference - plenty of posts on this forum about the bore and stroke of tx200s and hw97's, something like 26mm bore x 80mm stroke, about 40cc of air.
A 12 ft PCP would need something like 3 times that much air, maybe a bit more for a .177.

Note that doesn't mean springers are necessarily 3 times more efficient than PCPs though!

BB

65.3cc's by my maths ,

As I said above, in a PCP the energy that you have put in to the springers spring when you compress it cocking the rifle for each shot, does not exist so that stored effort/energy has to come from extra compressed air.

For a given pellet in a given bore & barrel length, the energy (from the compressed air) required to reach a specified muzzle velocity will be exactly the same ( vol A), so the shot is equally efficient.

BUT to replace the energy from the spring you need another 150%ish of vol A (vol B).
All vol B does is push vol A in to the breach it then exits the muzzle as wasted air once vol A has shot the pellet out.

In a gas ram vol B is contained inside the ram, but You again have to impart the energy in to the gas by physically cocking the rifle to compress the gas for each shot.

[RobF]

65.3cc's by my maths ,

As I said above, in a PCP the energy that you have put in to the springers spring when you compress it cocking the rifle for each shot, does not exist so that stored effort/energy has to come from extra compressed air.

For a given pellet in a given bore & barrel length, the energy (from the compressed air) required to reach a specified muzzle velocity will be exactly the same ( vol A), so the shot is equally efficient.

BUT to replace the energy from the spring you need another 150%ish of vol A (vol B).
All vol B does is push vol A in to the breach it then exits the muzzle as wasted air once vol A has shot the pellet out.

In a gas ram vol B is contained inside the ram, but You again have to impart the energy in to the gas by physically cocking the rifle to compress the gas for each shot.

Check your maths

Volume of a cylinder = π x R² x L

3.1416 x 1.3² x 8 = 42.27 cc

That's mine.

I think there's an assumption that air is like a liquid and that the pellet is pushed all the way down the barrel by a consistent volume. That's not the case and it's a highly complex system to do with pressure waves and flow, which aren't the same things.

I agree the comparison with springers and other plants is flawed because of the stored energy of the power plant (Spring/Ram)

[angrybear]

Check your maths

Volume of a cylinder = π x R² x L

3.1416 x 1.3² x 8 = 42.27 cc

That's mine.

I think there's an assumption that air is like a liquid and that the pellet is pushed all the way down the barrel by a consistent volume. That's not the case and it's a highly complex system to do with pressure waves and flow, which aren't the same things.

I agree the comparison with springers and other plants is flawed because of the stored energy of the power plant (Spring/Ram)

26mm x 80mm or as we want it in cc's 2.6 x 8 so - pi x D x L

3.142 x 2.6 = 8.1692 x 8 = 65.3536cc's swept volume

[BTDT]

26mm x 80mm or as we want it in cc's 2.6 x 8 so - pi x D x L

3.142 x 2.6 = 8.1692 x 8 = 65.3536cc's swept volume

3.142 x diameter = circumference. Circumference x length = surface area of the cylinder in square cms.

Try 3.142 x radius x radius x length for volume in cubic cms.

[angrybear]

Yep, You beat me to my correction confusing my circumference of a circle, with my surface area of a circle.

silly old bear