Power Plenum on .25 cal., 600mm slug liner and 33.5gr NS slug

To my understanding increased plenum volume isn’t going to gain more power unless the current plenum volume is being dumped before the pellet exits the barrel. If restrictions (ports) are limiting your power you need to attack those first. If valve opening time is limiting your power you need to attack that first. Only then will you get to the point where plenum volume will have an effect on power.

On the other hand, at power settings below maximum, there might be the capability to increase efficiency with a larger plenum because a more consistent dump of air can occur at a lower reg setting allowing one to shoot to lower bottle pressures. This effectively yields more capacity from the existing bottle volume.

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You are absolutely correct. But my experience shows the upgrade kit of PP “alone” will never catapult a 34 gr slug pass 900fps. As such, i will end up shooting pellets because pellets are stable than slugs at the speed that is less than 900fps. 
I doubt people bought the pp kit just for the gained number of shoots.

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To my understanding increased plenum volume isn’t going to gain more power unless the current plenum volume is being dumped before the pellet exits the barrel. If restrictions (ports) are limiting your power you need to attack those first. If valve opening time is limiting your power you need to attack that first. Only then will you get to the point where plenum volume will have an effect on power.

On the other hand, at power settings below maximum, there might be the capability to increase efficiency with a larger plenum because a more consistent dump of air can occur at a lower reg setting allowing one to shoot to lower bottle pressures. This effectively yields more capacity from the existing bottle volume.

Click to expand...

You are absolutely correct. But my experience shows the upgrade kit of PP “alone” will never catapult a 34 gr slug pass 900fps. As such, i will end up shooting pellets because pellets are stable than slugs at the speed that is less than 900fps. 
I doubt people bought the pp kit just for the gained number of shoots.

Click to expand...

I dont understand that as a stock mk2 before bigger plenum with just opening up transfer ports on barrel and probe was able to get 34gr pellets to 950 without much difficulty.



also in .22??



i Think that the caliber is a Big factor 

if you have a .25 shooting 34gr it Will have easyer getting it to shoot at that speed then a .22 with a 34 gr becouse of the bigger size barrel.


i really just want to know what speed you can get out of a Stock impact with PP in different calibers

Click to expand...

To my understanding increased plenum volume isn’t going to gain more power unless the current plenum volume is being dumped before the pellet exits the barrel. If restrictions (ports) are limiting your power you need to attack those first. If valve opening time is limiting your power you need to attack that first. Only then will you get to the point where plenum volume will have an effect on power.

On the other hand, at power settings below maximum, there might be the capability to increase efficiency with a larger plenum because a more consistent dump of air can occur at a lower reg setting allowing one to shoot to lower bottle pressures. This effectively yields more capacity from the existing bottle volume.

Click to expand...

You are absolutely correct. But my experience shows the upgrade kit of PP “alone” will never catapult a 34 gr slug pass 900fps. As such, i will end up shooting pellets because pellets are stable than slugs at the speed that is less than 900fps. 
I doubt people bought the pp kit just for the gained number of shoots.

Click to expand...

I dont understand that as a stock mk2 before bigger plenum with just opening up transfer ports on barrel and probe was able to get 34gr pellets to 950 without much difficulty.



also in .22??



i Think that the caliber is a Big factor 

if you have a .25 shooting 34gr it Will have easyer getting it to shoot at that speed then a .22 with a 34 gr becouse of the bigger size barrel.


i really just want to know what speed you can get out of a Stock impact with PP in different calibers

Click to expand...

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Without any modification...

MK1 first generation regulator, .30 caliber...600 mm barrel....reg 150.....hammer spring adjustment wheel at max...JSB 44 grains pellets = 890 fps

Will get my PP installed soon with a 700 mm slug liner barrel and i am sure I will fine tune it and get 950 + fps with 44 grain slugs at 120-130 regulator pressure.

The only modification i plan to do is using the original 52 mm hammer spring and maybe remove 2 or 3 coils on the return valve spring bumper.

There is no other magic things .

Just make sure to fine tune your Impact properly and do not rush.

Period.

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Good luck. With those modifications "you mentioned only" and the PP, your jsb 44 gr will be less than 920fps (the recommended speed for slugs). I am expecting you to post your result. I and some of of the readers will follow up from you and read all your post. Your failure to post means you failed. Walk the talk..

When you max all the numbers and the limit of adjustments, is that "fine tuning"? In computer terminology, you overclock your CPU. That is not fine.

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Hi Bob.

Thank you. But i need a stronger hammer spring to counter that pressure. If only i could buy a ready made spring, i might do it.

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