HPA pressure (long)

Talon SS CO2 on HPA

Wondering what pressure HPA tank to get? Debating ordering one and decided to find out
what pressure would be best for my set up.

Have lightened the hammer, trying for a sharp quick “blast” of co2 rather than a long “burrp” as the 12” barrel just doesn’t go any faster past a spring tension setting of “4” with the stock hammer. By lightening the hammer, it runs out of speed at a setting of “8”. Same velocity, but a bit quieter from the short sharp hammer strike. Normal setting is at “6” for back yard use. Top hat was adjusted to the maximum that would allow the bolt to close with just a hint of “slack”.

This is the HPA test set up:

Drill is to turn the on/off to “on”, pump the small chamber up to the test pressure, turn the on/off to “off”, vent the pump, and shoot one shot. Do that 5 times at each test pressure for a short average vel.

Spring tension set to “6”
Lightened hammer
Test pellets were 5mm Benjamin/Sheridan 14.3gr. Cylindrical

Results;
CO2 at a normalized temp. of 84 degrees = 588Fps/ 10.9 foot pounds

800PSI = 563fps / 10 fpe+
1000PSI = 605fps / 11.6 fpe+
1200PSI = 655fps / 13.6 fpe+
1400PSI = 685fps / 14.9 fpe+
1600PSI = 711fps / 16 fpe+
1800PSI = 470fps / 7 fpe+

So what the devil happened between 1600PSI and 1800PSI?

For the first time the valve had pressure left over after the shot. At lower pressures, all the air was used…past 1600PSI, the valve just wasn’t knocked open by the lightened hammer.

Retesting showed that at 1800PSI, the gun would give 3 shots…one at 470fps, one at 685 fps, and one at 270 fps.

So if I want to keep the same hammer set up, and want co2 type vel. in the winter months when co2 is nearly useless, would go with an HPA tank in the 850-900PSI out put range.

If i wanted the max. speed this hammer-valve set up can give, would go for something in the 1500-1600PSI out put range.

Am sure that by adjusting the spring tension to 11 or 12, would get better vel, for the higher pressures; going back to a stock hammer would help as well.

But if you’re wondering what HPA out put to order, this is an easy test to do.