Barrel length

[Blackdog]

What barrel length will give you the maximum FPS?

[Davio]

What gun?  CO2 or pump?  What caliber?

[Blackdog]

That would be a 2289 Backpacker.

[Flex]

What barrel length will give you the maximum FPS?

Like Davio says it depends on several factors. I've asked this question before too and have done more than a little bit of research. The bottom line remains "it depends" BUT it seems like many choose 18" as an optimum barrel length. What surprises me is, if that is true, why would Crosman NOT offer it as one of the available barrel lengths? I did buy the 14" barrel from Crosman to replace the 12" one that came on my 2289. I modded a 2240 by mounting an 18" .177 cal barrel (cut down from a 24" barrel from Crosman). I'm thinking of doing the same with a 24" .22 cal barrel so that I can swap calibers and lengths between the 2240 and the 2289. I paid less than $20 for the .177 cal barrel from small airgun shop and the .22 cal 24" barrel is ~$15 from Crosman. It's not all that difficult to cut and recrown. I did it with basic hand tools "down in the Man Cave".

BTW, I've been following a few of your posts and it's starting to look like you didn't do a very good job of hiding your wallet .
Flex

[BDS]

A 2289 is more affected by pumps and air pressure than barrel length (different dynamics than co2 optimum length). But.. a 14 will be slightly better than the stock barrel. My 2289 is amazingly accurate with the stock barrel so I have left it alone, and most 2289s I have read about this past year are also great right out of the box. Crosman got it right with this new version of the old backpacker.

[BillK]

With my limited experience and knowledge I say 24".  Not the handiest length for something other than a stocked rifle but it seems to produce the most FPS.

[Davio]

Air rifle barrel length lets the pellet accelerate. If your barrel length is less than what your gun needs for acceleration length, then you have thrown away some velocity.  If the volume of gas in the barrel increases to its maximum and there is remaining barrel, then it is no longer accelerating and the additional barrel length can cause drag (loss) of acceleration.

CO2 expands much more than air, so it can often utilize and have higher fps per inch gains from longer barrels. HPA and PCP (air) higher pressures will utilize additional barrel length more than a mundane stock 13xx valve with 10 pumps. So the stock 2240 will get some gain from a longer barrel.  But it will be marginal compared to the obvious seat of your pants gains that a BOSS valve and righteous porting can utilize in a 21" or 24" barrel. 

On your Backpacker with 12" barrel and stock valve?  Leave it alone.  If you make mods for more pumps and larger dumps then maybe you would get some gain by going to 18".

[DBOdude]

going by this posters results .......

http://www.network54.com/Forum/275684/thread/1318040664/1377+to+1322+upgrade,+my+results.++Need+stronger+hammer+spring-

in .22 cal. using 10 pumps or more the 24 inch barrel got significantly more fps than 10 and 14.5 inch barrels .
results are more impressive using a flat top piston and valve .

[BDS]

going by this posters results .......

http://www.network54.com/Forum/275684/thread/1318040664/1377+to+1322+upgrade,+my+results.++Need+stronger+hammer+spring-

in .22 cal. using 10 pumps or more the 24 inch barrel got significantly more fps than 10 and 14.5 inch barrels .
results are more impressive using a flat top piston and valve .

Ya but what Davio said... In stock form, barrel length is a small improvement if any, the OP has a 2289 in stock form.

[DBOdude]

so from 455ish to 513ish ..... . i dont have a chrono but my stock dbo hit harder with the 24 inch .22 barrel than the stock 12 incher , and the 24 incher was a little quieter . and with the F/T P&V the 24 hits harder and is slightly quieter than the 12 .... not that it sounded particularly with either shorter barrel . i dont know if my numbers were similar to the post i linked to , but i know it hit harder and FWIU results from similar mods can vary on different guns . i expected more and i got it so i'm happy . i think i'm gonna go to .177 though .