shots per fill/charge carbine v rifle

[Jaracas]

ive done a search but cant really get any real info on this.

i can understand there being a muzzle velocity difference between two rifles, one being a carbine and one full length, due to the fact that the blast of gas is trapped behind the pellet for a longer period of time during its exit.

but what i cant get my head around is the lower shot count per identical fill of a carbine.
surely the reservoir behind the pellet still holds the same volume of gas in the carbine and rifle? ergo every pellet would have the same amount per shot? meaning that the amount of pellets per charge would be the same, but the carbine would be less efficient?

excuse my ignorance here

[Charlts]

ive done a search but cant really get any real info on this.

i can understand there being a muzzle velocity difference between two rifles, one being a carbine and one full length, due to the fact that the blast of gas is trapped behind the pellet for a longer period of time during its exit.

but what i cant get my head around is the lower shot count per identical fill of a carbine.
surely the reservoir behind the pellet still holds the same volume of gas in the carbine and rifle? ergo every pellet would have the same amount per shot? meaning that the amount of pellets per charge would be the same, but the carbine would be less efficient?

excuse my ignorance here

Carbine's generally have smaller cylinders than rifles, hence the lower shot count.

I'm not 100% on this but I would imagine a shorter barrel would require a larger air blast to give the same MV as a longer one hence the drop in power when I fitted an S400 carbine barrel to my mates classic.

Ryan

[kevG]

the shorter barrel needs more blast of air to make up for being shorter,plus the air tube will be shorter and hold less air,thats two reasons

kevG

[kevG]

Carbine's generally have smaller cylinders than rifles, hence the lower shot count.

I'm not 100% on this but I would imagine a shorter barrel would require a larger air blast to give the same MV as a longer one hence the drop in power when I fitted an S400 carbine barrel to my mates classic.

Ryan

i will have to type faster

kevG

[Jaracas]

just i have two qb78's (well, one is an xs) and they are identical apart from one having a carbined barrel, i get roughly the same shots per carts and they are both around the same power, the carbine chronod at 11.7 and the standard at 11.4, thats why i cant get my head around it, lol, if anything, i get maybe half a dozen less on the standard length.
both are qbtune btw

[Slacker24seven]

the shorter barrel needs more blast of air to make up for being shorter,plus the air tube will be shorter and hold less air,thats two reasons

kevG

Exactly.

My .22 S10 Carbine does 150-ish shots per fill; whereas a full length one will do 200.

Quite a bit of difference between the two barrel lengths though, the inner barrel of an S10C is really rather short

[AirArmsDavid]

the shorter barrel needs more blast of air to make up for being shorter,plus the air tube will be shorter and hold less air,thats two reasons

kevG

Where is the pellet's maximum velocity then? Surely it's at an unknown point in its journey having started at zero, speeded up through the blast of air and then slowed down again due to air friction.

And if there's less barrel to cause friction wouldn't that need a smaller blast of air? Or does the air it emerges into have a higher coefficient of friction than steel?? I doubt that.

Assuming steel causes more friction than air, surely the LONGER the barrel the higher blast of air to provide the same MV, if MV = speed emerging from the barrel end?

[Fluffybuck]

just i have two qb78's (well, one is an xs) and they are identical apart from one having a carbined barrel, i get roughly the same shots per carts and they are both around the same power, the carbine chronod at 11.7 and the standard at 11.4, thats why i cant get my head around it, lol, if anything, i get maybe half a dozen less on the standard length.
both are qbtune btw

Perhaps one gun has more efficient valving than the other.
I have two HW100K's in .177. One gives 65 shots per fill. The other gives 45.
One must have been assembled by HW's top smithy, while the other was probably done on a friday afternoon by a work experience kid.

[Fluffybuck]

Where is the pellet's maximum velocity then? Surely it's at an unknown point in its journey having started at zero, speeded up through the blast of air and then slowed down again due to air friction.

And if there's less barrel to cause friction wouldn't that need a smaller blast of air? Or does the air it emerges into have a higher coefficient of friction than steel?? I doubt that.

Assuming steel causes more friction than air, surely the LONGER the barrel the higher blast of air to provide the same MV, if MV = speed emerging from the barrel end?

PCP's can keep accelerating a pellet for probably 60cm of barrel - and probably more, but I have never laid my hands on a barrel longer than 60cm.
PCP's are incredibly wasteful of the energy in the air blast - hence the loud muzzle crack.
So a long barrel on a PCP allows more time for the energy in the air blast to transfer to the pellet.

Springers don't usually accelerate the pellet after the first twelve inches - and often less than that.

[AirArmsDavid]

PCP's can keep accelerating a pellet for probably 60cm of barrel - and probably more, but I have never laid my hands on a barrel longer than 60cm.
PCP's are incredibly wasteful of the energy in the air blast - hence the loud muzzle crack.
So a long barrel on a PCP allows more time for the energy in the air blast to transfer to the pellet.

Springers don't usually accelerate the pellet after the first twelve inches - and often less than that.

Whilst you were writing that I was talking to John Bowkett as it was bugging me! He said precisely the same thing - are you related!!??

One difference he mentioned was with regulated or tuned guns where the rifle barrel length has been included in calculations and so the blast provides the correct energy.

[saclang]

Whilst you were writing that I was talking to John Bowkett as it was bugging me! He said precisely the same thing - are you related!!??

One difference he mentioned was with regulated or tuned guns where the rifle barrel length has been included in calculations and so the blast provides the correct energy.

I am so glad you added this info as next week I plan to have a chat with JB and a shorter barrel was one issue that was bugging me

Steve

[Rich]

Getting just enough air - and only just - to get the pellet up to speed at the instant it leaves the muzzle is the holy grail that Daystate are pursuing with their latest published technology.

A typical 12fpe knock-open PCP will use something like four times the amount of air that a springer will.

What gives the springer the advantage here is that the air is compressed by the piston adiabatically, that means it gets hot and this leads to the air "swelling" just at the time the piston is compressing it, so the rise in pressure behind the pellet is much higher than might be thought.

A bicycle pump gets hot when you use it, and after a few seconds pumping you start to feel it. The compression phase of a springer being fired happens so quickly that this heat is not absorbed by the metalwork and goes into the air instead.

[Fluffybuck]

Whilst you were writing that I was talking to John Bowkett as it was bugging me! He said precisely the same thing - are you related!!??

One difference he mentioned was with regulated or tuned guns where the rifle barrel length has been included in calculations and so the blast provides the correct energy.

Related? No. I have never met him.
Although I have high regard for him and his abilities, I have probably slated BSA guns a few too many times to be on his Christmas card list.

Optimising barrel lengths to powerplants has been a "on-and-off" study of mine in recent years.

[Jaracas]

i'm going to swap barrels and see what transpires, lol

[sharky]

The reason why your seeing differant results with you 78's is because they're co2 powered which is differant to pnuematic powered rifles. Co2 behaves totally differant to compressed air.