An Idea! Will It Work? Has It Been Done?

An Idea! Will It Work? Has It Been Done?

Joined: March 17th, 2007, 1:07 pm

August 20th, 2011, 2:42 pm #1

Ive been thinking of ways to improve the power on my 2250 which has a shortened barrel. Its obvious the co2 is wasted as the pellet leaves the barrel. I was wondering if I use a hollow probe and drill out the center this would allow the gas to expand a little before the pellet starts its journey and use more of the gas available before it exits the barrel?

[/IMG]

Or would the power be reduced because the initial blast may be lower? Anyone tried it? Any thoughts?
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Joined: April 1st, 2009, 3:18 am

August 20th, 2011, 2:57 pm #2

Try it to see. C02 is an expanding gas, so the trick may work. It's always worth a try in this hobby.

"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."

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Joined: November 28th, 2002, 6:26 pm

August 20th, 2011, 3:04 pm #3

Ive been thinking of ways to improve the power on my 2250 which has a shortened barrel. Its obvious the co2 is wasted as the pellet leaves the barrel. I was wondering if I use a hollow probe and drill out the center this would allow the gas to expand a little before the pellet starts its journey and use more of the gas available before it exits the barrel?

[/IMG]

Or would the power be reduced because the initial blast may be lower? Anyone tried it? Any thoughts?
...dead volume, etc. But whatever you call it, any unnecessary space (i.e., that doesn't at least contribute to free gas flow) between valve and pellet allows unwanted pressure drop and is generally a bad thing for power and efficiency.

Steve
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Joined: March 17th, 2007, 1:07 pm

August 20th, 2011, 3:17 pm #4

The idea came from seeing paintball gun expansion chambers. These have fins which allow the co2 to expand more rapidly. Although I think they give consistancy gains under rapid fireing rather than power gains.
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Joined: November 28th, 2002, 6:26 pm

August 20th, 2011, 3:50 pm #5

...(which would be more properly called: "heat exchangers") actually install upstream of the valve (i.e., between gas supply and valve). So they don't contribute the pressure-squandering dead volume and headspace you'd get if you added unnecessary volume downstream of the valve (i.e., between valve and breech) as in your sketch.

Steve
Last edited by pneuguy on August 20th, 2011, 3:55 pm, edited 1 time in total.
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Joined: March 17th, 2007, 1:07 pm

August 20th, 2011, 4:11 pm #6

Completely overlooked that fact.
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Joined: April 12th, 2002, 5:26 am

August 20th, 2011, 5:10 pm #7

Ive been thinking of ways to improve the power on my 2250 which has a shortened barrel. Its obvious the co2 is wasted as the pellet leaves the barrel. I was wondering if I use a hollow probe and drill out the center this would allow the gas to expand a little before the pellet starts its journey and use more of the gas available before it exits the barrel?

[/IMG]

Or would the power be reduced because the initial blast may be lower? Anyone tried it? Any thoughts?
chamber and a lighter striker.
Last edited by classicalgas on August 20th, 2011, 5:10 pm, edited 1 time in total.
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Joined: March 17th, 2007, 1:07 pm

August 20th, 2011, 5:30 pm #8

Ive already done some basic valve mods. (removed threads and bored valve cap, angled port etc) My goal is 12ftlbs but would be happy with 10ftlbs. Im currently at 8ftlbs. Perhaps a tall order using capsules? There is definatly still room for a little improvement but I cant see where im gonna get an extra 4ftlbs without thinking outside the box?
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Joined: July 6th, 2005, 5:26 am

August 20th, 2011, 6:14 pm #9

A short barrel is more at home with air. A flow through bolt, a really quick opening valve and a long barrel is the only things I know of for increased FPE. The valve stroke need not be very long but it needs to open faster than a stock valve as in a light striker and a strong spring. bulk is a must also. My 2260 is at 20FPE. john
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Joined: September 25th, 2006, 2:19 pm

August 20th, 2011, 7:39 pm #10

...dead volume, etc. But whatever you call it, any unnecessary space (i.e., that doesn't at least contribute to free gas flow) between valve and pellet allows unwanted pressure drop and is generally a bad thing for power and efficiency.

Steve
Considering the *striker mechanism and the heavy ex valve spring, I am thinking the lift and duration of the ex valve is independant of the realitivly low reservoir pressure used in this rifle. Therefore I would think that the lift and duration would be same at lowest reservoir pressure as at high reservoir pressure.

That leaves a huge "lost volume" transfer passage to possibly pressure up (at lowest reservoir pressure) before the shot ball even moves. The ball would stay put owing to it's own inertia, static friction and possibly a bit of intentional restriction at the breech to prevent the shot ball from rolling out of the barrel since a patch was not used.

So when viewing the plan view of the Girandoni, could it be that the huge transfer passage we see was actually necessary/required for the proper function of this rifle?

* I am aware that there is a differance of opinions on how the striker mechanism functions. I am assuming that the striker disengages from the ex valve and with a stout ex valve spring, the lift and duration remain constant throughout the gambit of reservoir pressure variations.

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