Testing 3 .177 barrel lengths on the 2240 platform

[Poorman Plinker]

Here are the results of testing three different .177 barrels on a 2240 platform. Do not generalize these results that were first posted on the Crosman/PoormanPlinker facebook group as they relate only to a factory 2240 and only to factory Crosman barrels shooting factory pellets.

The velocity was measured 16" from the muzzle and a weakness of the study is that the shooting stand had to be moved to accommodate the various barrel length distances from the chrono. Crosman Premier Pointed 7.4g pellets were used and 6 shots were wasted before each test to help level the co2 charge. A total of 15 shots were then fired after which a new powerlet was used. Temperature was 75 degrees (+&- 1) and humidity was 79%.

The only gun modifications were changing the 2240 barrel band for 2 Disco barrel bands (one placed against the trigger frame and the other 3/8" from the tube end) and the factory brass bolt had been replaced with a factory steel bolt, both of the same dimension. Barrels were tested from the longest to the shortest barrel. Shots were fired with only the time necessary to load the next round and aim between shots.

It should come as no surprise that both the peak and average velocities increased as the barrel length increased. What does come as a surprise is how the shot count within 15 fps changed.
What is generally considered most important is the velocity gain...
Posted as barrel length/average fps of 15 shots:
10.25”/546fps  - 18”/642fp  -  24”/644fps
 
By examining the fps as it relates to the change in length in inches one could infer that a complete demise of acceleration would occur past 24”. The following are the fps difference from the longest to the shortest barrel: 24” fps - 18” fps = 2 fps, and;18” fps -10.25” fps = 96 fps. There seems to be not much velocity advantage to having a 24” barrel compared to an 18” barrel in .177 using co2.

The shot count within 15 fps went from highest (14) in 10.25" and (13) in18", and; to the lowest (10) in the 24". The Standard Deviations of the 10.25” barrel was 7 compared to 6 in the other two barrels. The difference in SD seems incongruous because the 10.25 had the highest number of shots within 15 fps, however it did have the largest overall spread. The 10.25 inch barrel was the only one in which the velocity was very peaky, erratically going up and down. The two other barrel's velocities started low and rose to a peak and then declined much more uniformly. In this test the 18” barrel seemed to perform the most level of the three.

[ev-in-az]

This subject gets revisited with various opinions and data from time to time, let me add more information

https://www.pyramydair.com/blog/2007/07/how-barrel-length-affects-velocity-in-a-co2-rifle/velocity-in-a-co2-rifle/

https://www.pyramydair.com/blog/2015/02/crosmans-2400kt-carbine-part-5/

A multi pump 1377 does however show an increase in muzzle velocity with a 24" barrel compared to an 18".

[shanejohnson2002]

Old post, I know...but I have gone back and forth between CO2 and HPA conversions on this platform in both .22 and .177, so I have some experience here.

It has been my observation that CO2 in a .177 runs out of "steam" at around 18", whereas an HPA-converted 22xx or 17xx can see real velocity gains all the way out to 24" (with diminishing returns, of course).

My .22 has only ever been 18", but the difference between CO2 and HPA was phenomenal...about 100-150 fps, if I recall correctly. And all I did was remove the valve stem and insert a HiPac.

YMMV.

[Poorman Plinker]

Hi Shane,

I am going to figure out how to compress my photos some day and post the charts I have on CO2 vs. HPA and .177 vs .22.
There are so many variables my results will be mine only...
Sorry so slow to reply just up to the gun rails with work.
Poorman

[avator]

You gentlemen know you're going to wake the sleeping giant with this thread right? Mr. Sterne is gonna bring out his spreadsheets...

[rsterne]

No I'm not, but I will throw in an observation.... My experience with CO2 is that in .22 cal a 24" barrel has significantly more velocity than an 18", but the difference is not as great as between 18" and 12".... I have not done the testing in .177 cal to comment.... I would make one other observation, however.... All testing must be done at the same temperature, and with the same RATE OF FIRE.... because CO2 cartridges cool a lot during use.... It would be best to leave 1 full minute between shots when doing this kind of comparison.... but it is critical that you use the same time increment between shots in all tests, or you can skew the results in favour of the more widely spaced shot string....

Bob

[avator]

Bob, your name was the first thing that came to mind when I read this thread. I have read your experiences over and over concerning volume, expansion and such. You've, no doubt, forgotten more about this topic than I'll ever know.

[Poorman Plinker]

 Now that you mention it... there are many problems when comparing "average" FPE. Average over what? A 12% decrease in velocity? (my favorite) Until the gun runs out of CO2? Until the velocity reaches a predetermined speed? (I use this too) Or First shot? or Highest speed per shot string? Then there is the shooting sequence/procedure (as Mr Sterne mentioned)...is there cooling? What is the ambient temp? You catch my drift...