converted 2240 to .177 and am getting less shots/cart

[Can-o-cide]

I cut 3/16" off the hammer spring on the 2240 and the shot count went up from 35-40 to 60-65 good shots per powerlet. I bought a 1377, and switch barrels and breeches so I have a 1322 and a 1740 now. When I was shooting today, I noticed I wasn't getting many shots, so I counted and the 1740 is getting about 50 good shots per powerlet.

there is no leaks, I left a full cart pierced in the gun for an hour, and again only got 50 shots per powerlet.

it is hot here. The gun was sitting in the sun, but it was partly cloudy and 95*F today.

after shooting 50 shots, I remove the power let, and there is either a typical amount of co2 released, or maybe a tad more, not sure.

the power lets are coming from a box of 40 that I bought awhile back, and some carts are completely empty and the necks of the carts are bent on some carts. It's possible that I grabbed some partially empty carts, but unlikely since I got exactly 50 good shots for 5 carts in a row....

what's going on here? I was expecting 90+ shots....

EDIT

I checked the hammer spring, and I definitely did not accidentally switch hammer springs.

with the 2240, I was not getting a co2 spray with a fresh cart. With the 1740, I'm getting a spray for the first 10 shots or so.

I think the problem is that the 1740 needs more of the spring cut off to see an increase in shot count compared to the 2240. That or the hammer spring is too short for the 1740 and the valve isn't opening enough with the co2 pressure being so high because it's so hot.

I personally feel that 3/16" isn't enough for the 1740, and that I need to cut more off to increase shot count. I think this because the 2240 by design is a gas hog, and converting it to .177 makes it even worse. With a co2 gun, the valve should close before the pellet leaves the barrel. With the smaller volume of the .177 barrel (both .22 and .177 barrels I use are 10") and the slight increase of velocity, the .177 pellet will be further down the barrel than the .22 when the valve closes, but not too far so that the .177 has more volume behind it than the .22.

I think the co2 spray with the .177 is what is creating the loss. What I don't understand is why the .177 sprays liquid co2 and the .22 doesn't...

[rsterne]

You will have to tune it down more for .177, it's releasing (or trying to) the same amount of CO2 as before, with a lot of it blowing out the barrel after the pellet leaves.... I have a 2250 with a 14.5" barrel that gets 120 shots per cart. at 500 fps in .177.... and shoots the same velocity at all temperatures from freezing to 75*F.... You get fewer shots when cold, however....

Bob

[Can-o-cide]

I was editing my post when you posted...

thanks man, I was hoping you'd answer because I know you have a lot of experience with shortening the hammer spring (and many other things!)

i guess I'll have to keep two springs if i want to switch the barrels back and forth

[longhunter]

I was editing my post when you posted...

thanks man, I was hoping you'd answer because I know you have a lot of experience with shortening the hammer spring (and many other things!)

i guess I'll have to keep two springs if i want to switch the barrels back and forth

or, you could get a rear velocity adjuster. Alchemy Airwerks makes a really nice one. ( shameless plug ) . I put one on my 2400KT, before I put it up for sale. the range of adjustability is pretty wide. if you order one, ask David for the one that HE makes. it's got more adjustability than the other two versions he carries. ( his words ).

[Can-o-cide]

For $35 those aren't a bad deal...

EDIT
what I have decided to do is cut the hammer spring some more. If I ever switch back to .22, I'll try it out and if I'm getting poor performance I can always shim back to whatever I cut off, or I can make my own PA using the .22 rimfire case and bolt through the endcap method.

I just cut another 1/16" off the spring (I.e. A half coil) and will report the shot count when I get a chance. I'm looking for as close to 100 shots/powerlet as I can get so that I use only one cart per typical shooting session. I haven't found any information posted about spring length versus shot count for a 1740, so it'll be good to compile this info. Rsterne has a post on this, but only reduced the spring by 1/8", so further lengths will be good to know.