CO2 barrel length

CO2 barrel length experiments.

Test rifle: Talon SS (co2)

An externally rusty spare 24” Crosman 2260 barrel was fitted with black delrin bushings and fitted to the Talon frame. After cutting the breech to remove the transfer port and recrowning, the barrel was a fraction over 23” long.

The barrel was cut and recrowned for each length; the first cut was 3” to 20” even. From 20” on, cuts were made in 2” increments until 12” was reached.

ALL the other parts (spring, hammer, valve, etc.) were the same for each length tested. This rifle had already been fitted with a lightened hammer, and that hammer was retained though out the tests. Crosman premiers (14.3gr.) used for all tests. Vel. readings are from 5 shot averages (and rounded to whole numbers). No end cap was used. Test temp. was stable at 71 degrees for all tests and the rifle was allowed 2 min. between each shot to stabilize temperatures.

(Test was carried out from inside my workshop, which can be heated and checked with a thermometer to maintain stable temperatures. This limited the lighting, and required the chronograph to be placed 7 yards down range, so vel. listed need to be adjusted to reflect muzzle vel. A good ball park adjustment would be +20 fps for each figure.)

Power setting:

5 10

23” 628 668

20” 625 648

18” 611 631

16” 604 618

14” 598 611

12” 576 602

Just goes to show the unpredictability of co2. Some steps showed as much as 8.5 fps change per inch while other steps only showed 3.3 fps change per inch. Overall, it’s close to 6 fps per inch.

(1) If considering a drastic change in barrel length ( + 6” of change), think 6 fps per inch would be close.

(2) If you are contemplating a small change in length (2”), don’t be too surprised to find the amount of increase to be unpredictable.

(3) Unlike other published tests, did not find that there was a reduction in velocity when barrels longer barrels were tried. The Talon’s valve undoubtedly moves more co2 than the valve on the test guns used in those reports.

Some notes:
Once the barrel length became shorter than the frame, the noise became quite loud. A 12” barrel with out an end cap seems to use the frame as a noise enhancer.

Considering the use I’ll put this co2 powered rifle to, settled on a 16” barrel. Used a 2nd Crosman 24” barrel (this one not so ugly on the outside) to make the 16” barrel. WHAT shot well certainly changed,b ut 25 yard groups with favored pellets are within 1/16” of the 12” AirForce barrel. Luck of the draw, can’t expect every $14 Crosman barrel to shoot well. This 16” barrel needs larger diameter pellets with deeper hollow skits to shoot well.

With the power setting at #5, averaged 602fps at 7yards (call that 620fps muzzle vel.) and works fine out to the 25-30yards my back yard allows. A new, two baffle, 2 3/4”” longer than the frame, end cap seems to quiet this 12 foot pound rifle quite nicely.