Tuning Diana Chaser .177 pistol, 150 shots

[nobody1]

I like CO2 air guns as .177 pistols, lower powered and with lots of shots for target shooting.

I prefer CO2 pellet (as opposed to BB replicas) pistols, and my favorites are Diana Chaser and the Crosman 2240.
Diana Chaser is better all around than the 2240.

I have tuned a .177 Chaser pistol to shoot 150 shots on 1 CO2 cartridge.

With 7 grain pellets the first 90 shots were in the 340-360 FPS range, and shots 90 through 150 were in the 360 to 430 FPS range.
Yes, the velocity climbed up to about shot 135 and peaked at 425-430 FPS then went down and reached about 340 FPS at shot 150.
The temperature was in the 60-70 range.

I have almost got bored shooting all those shots in one session but wanted to count the number of useable shots.

To tune it that way I used a shorter and stiffer hammer spring, so short that it rattles in the air gun.

 

[marflow 777]

so when make a post like this, you tell us how it was done and most of us can follow along and understand
BUT tell us the spring you used and where you got it
DETAILS are important

 

[nobody1]

I have replaced the spring last year.
I do not remember the dimensions.

The main thing is to have a ticker wire than the original hammer spring.
If the original hammer spring has 0.8mm wire then try using 1mm wire.

Initially cut the new hammer spring (with a ticker wire) close to the original hammer spring.
Shoot a few shots and measure the velocity.
At first the velocity may be higher.
Keep cutting the hammer spring (less than 1 coil) and measure the velocity.

When you get to the velocity range you want then stop cutting.

 

[marflow 777]

well, that is how all R&D work is done no mystery there.
i will leave my 6 Chasers as they are

 

[Treefrog]

That's impressive! What's the total ft/lb yield?

The best I've been able to get so far is 55 useful shots from a single cartridge and 93 from two (in a .22 rifle). That's 352 and 716 ft/lbs respectively.

Cheers,

J~

 

[beerthief]

That's impressive! What's the total ft/lb yield?

The best I've been able to get so far is 55 useful shots from a single cartridge and 93 from two (in a .22 rifle). That's 352 and 716 ft/lbs respectively.

Cheers,

J~

feet per second not foot pounds energy

 

[Hold_Over]

Are the mechanics of the chaser similar to or the same as the airbug?