Barrel length vs volocity

[slivershooter]

Hey guys, I have been otherwise occupied for some time and just now getten back to my AG's.  Got a question that maybe has been answered many times but I'll start a fresh thread here.  At what length does the length of a barrel become a drag on the pellet in a Co2 gun.  I can see that much is wadted on a short barrel and volocities are higher with a longer barrel, But there is a point that the psi's are dropping.

[breakfastchef]

This is a decent resource that addresses your specific question.

http://www.pyramydair.com/blog/2007/07/how-barrel-length-affects-velocity-in.html

[BillK]

I  wonder if 18" is best why Crosman makes 24" barrels.  Seems if you have enough power the longer the better.
Makes me wonder....

[T191032]

Do some searching around here on the board, several of us had done some testing with various lengths. 

[breakfastchef]

I  wonder if 18" is best why Crosman makes 24" barrels.  Seems if you have enough power the longer the better.
Makes me wonder....

Going to guess that after 18", there is no more additional expanding pressure from the initial blast of CO2 out of the valve, and the final 6" of barrel length adds drag to a non-accelerating pellet.

[KevinP]

Going to guess that after 18", there is no more additional expanding pressure from the initial blast of CO2 out of the valve, and the final 6" of barrel length adds drag to a non-accelerating pellet.

well said ...   

[BDS]

Purrty-much... the gas expansion has a finite level (barrel length) given the small volume of co2 available.

[BillK]

Perhaps .22 is different from .177 .  Back in Nov. 2013 Airriflenut was changing/checking barrels on his .177.  The 24" shot 703fps while the 18" shot 677fps. 
I guess I'll have to put an 18" barrel on my 2260 and see what the difference is.
Seems if the valve is low power than a longer barrel would/could slow down a pellet from the added friction of the longer barrel.  So, is a 2240 valve powerful enough for a 24" barrel?
This is getting above my ability to conceptionalize.
.

[tinker]

The best I ever got out shooting CO2 was a 724fps average out of a 24" .22 barrel shooting 14.3gr. pellets.  The rifle was bulk fed using a 9oz. bottle and an Archer tank block mounted with 4 screws.  The valve was a gas hog and I got just 6 shots out of a 12 gram cartridge.  Using a shorter barrel it couldn't break 700fps.  No I didn't get a hundred of shots either.   Not to efficient build.  The CO2 usage was too high for the fps I got.  I think I used a lot of the parts for my 1st Disco build!

Glen

[targettgii]

Tinker I believe that those are the key words bulk fed or hpa.I think (my own opinion here)having not done any testing that a higher volume power supply would enhance the longer length barrel rather than hinder it.And with a 12 gram power supply you get so much power behind the pellet then that is it.

[agninja]

Perhaps the longer 24" barrel is for the sake of accuracy, if not additional power. Though I can't imagine there being much of an appreciable difference for either. With the 24" being simply too long and unwieldy for such a small platform, I would never get one anyway.

[tinker]

Yes the key was bulk fed Tom.  Even with the 24" barrel she spewed CO2 out the barrel just like a stock 2240 with a fresh cartridge with every shot! 

[slivershooter]

Thanks for the input guys. I kinda had the feeling that at some point, longer barrel lengths would be a drag cause the UMFF is gone.

[targettgii]

i was just saying what I was thinking like I said it was my opinion an untested one at that.

[BDS]

Tinker noted the key fundamentals with co2. It's a fine line between optimum velocity and shot count, especially with co2. With a nominal pressure of 830 psi regardless of volume, the amount of gas used per shot starts to become "waste" as a function of "filling" the longer barrel for each shot.

On barrel length vs. accuracy, many of the best quality airguns have 12" and 14" barrels and are one-hole shooters, (HW, FX, Air Force etc).