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PostPosted: Mon Jan 19, 2015 6:37 am 
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Joined: Mon May 26, 2014 1:08 am
Posts: 480
Location: Thunder Bay
joe hickey wrote:
Regarding this topic, I have a question that I cant seem to find a suitable answer to. That is, In a spring powered air rifle, which is more desireable or a better use of air, 'faster' moving air, or, 'more', air behind the pellet.

Hi Joe.
Maybe this will help: A friend gave me a few non-working pellet rifles to play with. A relum telly, super telly, and a taurus, all made in Hungary.
The Super Telly is going to need a lot of TLC to shoot, but the other two are shooting well. All three have leather seals.
The Telly has a short stroke and a heavy spring. Cocking force required is about 28 lbs. The gun shoots 540 fps.
The Taurus has a much longer stroke and a very weak spring. Cocking effort is only 9 pounds. I can cock it with my little finger. Velocity is 550 fps.
Even with the obviously faster lock time in the telly, the taurus is by far the more accurate rifle. Sure, there are many other factors that contribute to the differences, but this example seems to bear out what others are saying, there is just no substitute for cubic inches.

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PostPosted: Mon Jan 19, 2015 8:38 am 
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OK so let me see if I'm understanding this correctly. In a springer, its volume thats most important. In PCP its pressure/air speed, And C02 its barrel length/hammer strike/volume ?

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PostPosted: Mon Jan 19, 2015 12:00 pm 
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Well.... sort of.... How much pressure for how long is the bottom line in all types of airguns....

The swept volume of a springer determines how much pressure can be developed (and for how long) for a given caliber, and ultimately pressure is what pushes the pellet, the volume maintains that pressure as long as possible.... Barrel length is relatively unimportant because the pressure pulse is so short.... pistols being the exception, of course (they may benefit from a longer barrel)....

In a PCP or Pumper, the pressure and barrel length determine the maximum possible power, for any given caliber.... The size of the porting determines to some extent how much of the reservoir pressure ends up pushing the pellet, and the valve dwell and barrel length determine for how long.... In a "pump-and-dump" the valve is open until the pellet exits, so barrel length is a major factor, (as is the valve volume, which determines the amount of air released).... true for all pneumatics....

In a CO2, the pressure depends on temperature but is still important, which is why CO2 changes velocity with temperature.... The dwell is often enough to waste CO2 in pistols by blowing CO2 out the barrel after the pellet has left, like most pumpers.... This may or may not be the case in a rifle, depending on dwell, so barrel length is very important.... In all forms of pneumatic (PCP, CO2, pumpers) the hammer strike (assuming it has one) determines the dwell.... and therefore the amount of CO2 (or air) used per shot....

Clear as mud?....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Mon Jan 19, 2015 12:15 pm 
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Location: Thunder Bay
There is quite a discussion going on on the yellow forum (network54) about piston bounce and combustion. Lots of good opinions and observations. There`s a good description of the controlled-combustion-piston-bounce hypotheses in contrast to detonation. It`s a good read, whether you agree with it or not.
Seems to fit with Òccam`s Razor!

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12 springers and a couple of pumpers.
2 lathes and lots of scrap metal.

I'm not multitasking. I'm doing something else until I remember what I was doing.


Last edited by ricksplace on Mon Jan 19, 2015 12:24 pm, edited 1 time in total.

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PostPosted: Mon Jan 19, 2015 12:20 pm 
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Location: Okanagan,BC
ricksplace wrote:
There is quite a discussion going on on the yellow forum (network54) about piston bounce and combustion. Lots of good opinions and observations.
I don't think I'm supposed to link another board when I'm on this one.


Go right ahead.

8)


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PostPosted: Mon Jan 19, 2015 12:26 pm 
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Joined: Mon May 26, 2014 1:08 am
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Location: Thunder Bay
Here ya go:
http://www.network54.com/Forum/79537/me ... od.SteveNC

Enjoy!


edit: the response from Steve in NC has a number of links in it.

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12 springers and a couple of pumpers.
2 lathes and lots of scrap metal.

I'm not multitasking. I'm doing something else until I remember what I was doing.


Last edited by ricksplace on Mon Jan 19, 2015 12:29 pm, edited 1 time in total.

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PostPosted: Mon Jan 19, 2015 12:28 pm 
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My thought has been why not make a bigger/wider piston chamber along with the piston and spring there for creating more volume. .....No :?: :?
similar principle to the piston in a car engine bigger piston = more power/compression with the same stroke.

In regards to spring bounce that all comes down to the actual spring itself, I believe this occurs in low end springer's much more then high end, you ever try to compress a good springer's spring ? you wont be able to budge it with your hands, that's why you always hear the term very little recoil or vibration just a solid thump from high end stringer owners, that's because there's a very good spring in the unit and has very little to no play in the tube, perfect example would be the HW97 for those who have shot one its just a solid thump. 8)

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PostPosted: Mon Jan 19, 2015 7:32 pm 
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Yep, larger diameter piston will increase the swept volume, requiring a larger, heavier, stronger spring (piston area goes up with the square of diameter, so does the force required to drive it).... The result will be a much heavier cocking effort, heavier parts, generating wayyyyyyyyyy more recoil.... Pretty much the difference between a magnum springer and a standard one, as that's generally the difference, a bigger chamber, piston and spring....

One of the reasons that the big HW springers are so smooth is the 10 lbs. weight.... Nothing tames a springer like piling on the pounds.... You could probably build a .30 cal springer that put out 50 FPE, but to tame it would require a gun weighing over 20 lbs. and a 3 foot barrel to cock it.... Possible, yes?.... Practical?.... that's up to you....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Mon Jan 19, 2015 9:11 pm 
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Posts: 1079
Location: Calgary, Alberta
rsterne wrote:
Yep, larger diameter piston will increase the swept volume, requiring a larger, heavier, stronger spring (piston area goes up with the square of diameter, so does the force required to drive it).... The result will be a much heavier cocking effort, heavier parts, generating wayyyyyyyyyy more recoil.... Pretty much the difference between a magnum springer and a standard one, as that's generally the difference, a bigger chamber, piston and spring....

One of the reasons that the big HW springers are so smooth is the 10 lbs. weight.... Nothing tames a springer like piling on the pounds.... You could probably build a .30 cal springer that put out 50 FPE, but to tame it would require a gun weighing over 20 lbs. and a 3 foot barrel to cock it.... Possible, yes?.... Practical?.... that's up to you....

Bob


I'm rather intrigued by this.

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PostPosted: Mon Jan 19, 2015 9:30 pm 
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rsterne wrote:
Yep, larger diameter piston will increase the swept volume, requiring a larger, heavier, stronger spring (piston area goes up with the square of diameter, so does the force required to drive it).... The result will be a much heavier cocking effort, heavier parts, generating wayyyyyyyyyy more recoil.... Pretty much the difference between a magnum springer and a standard one, as that's generally the difference, a bigger chamber, piston and spring....

One of the reasons that the big HW springers are so smooth is the 10 lbs. weight.... Nothing tames a springer like piling on the pounds.... You could probably build a .30 cal springer that put out 50 FPE, but to tame it would require a gun weighing over 20 lbs. and a 3 foot barrel to cock it.... Possible, yes?.... Practical?.... that's up to you....

Bob

you correct in all aspects Bob, the weight thing is a factor and it did kind of slip my mind or maybe I just didn't want to except the fact that it would have to be built like a tank literally, :(

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