Cr2240 owners with chronographs

Message

TCooper · #1 Post by **TCooper** » Thu Oct 20, 2005 1:40 pm

Years ago I tested my TAU-7 pistol for temperature sensitivity. At 55F and 70F I was getting the same velocity. The famous LD Mark1 pistol also functions well at low temps with fairly stable velocity from 45F to 95F. The Mac-1 web site gives the details ( http://www.mac1airgun.com/ldpistol.html ). As Tim states "Valve duration is balanced w/ pressure by passing low volumes of high pressure or high volumes of low pressure to yield a nearly flat performance across the pressure spectrum."

Balancing a valve will help with cool temperature performance. I know the TAU-7 has a very light valve return spring and I can easily compress it between two fingers. It's like the tension of a ballpoint pen spring. The hammer spring is not overly strong. This helps create the situation that Tim describes in the above quote.

Maybe some Cr2240 owners can do a test. Chronograph your pistols at room temperature (70F/21C). Then either put your pistol outdoors (with thermometer) or put it in the fridge. Check velocity again and report results. Balancing your springs and working your ports may improve the performance in this area.
Another note about the TAU-7 is it's ability to deal with rapid fire shooting. My review shows the results from rapid shooting... shoot as fast as I can load. No change in velocity. Maybe test your Cr2240 in this manner and report results (rapid fire with warm pistol at room temp).

I am not trying to knock the Cr2240 but just get some interesting and desired information. Mod work may improve your results, or not.

Thanks,
Todd

TCooper · #2 Post by **TCooper** » Thu Oct 20, 2005 1:51 pm

Maybe someone can try some QB-78 rifles with the two tests.

- Cool temperature testing
- Rapid fire testing

Thanks,
Todd

ETA · #3 Post by **ETA** » Thu Oct 20, 2005 3:15 pm

I know for sure the QB and the 22XX guns will be affected by temperature.
The QB and 22XX have similar designs that have massive hammers compare to many other CO2 guns. On top of that, they also have huge contact area for the hammer to slide on. Any change in viscosity in the lube will slow down the hammer, so does the expansion and contraction of the hammer and tube body that it slides in.

Fine tuning and balance for consistency is also going to be tough for these guns, again, because of the massive hammer and large contact patch. You need big changes in spring force to over come the inertia and friction of the hammer.

#4 Post by **sniper** » Thu Oct 20, 2005 4:29 pm

ok, this my very stock 2240 just got it from LeBaron with the first cheap powerlet from WM just going in. Room temperature is 69.8 F. The shot is taken every 30 seconds max. or less.

520.3
515.2
517.7
512.1
499.9
531.8
522.8
487.3
478.0
479.8
471.4
475.5
473.6
476.6
472.3

razpizdiay · #5 Post by **razpizdiay** » Thu Oct 20, 2005 7:13 pm

say what?

it shot above 500fps stock? omg... makes me laugh, so much for their "restrictions"

TCooper · #6 Post by **TCooper** » Thu Oct 20, 2005 7:57 pm

Hi Sniper,

What pellet are you shooting to get over 500fps? You seem to have a very "hot" 2240. Someone once did a test for me and got 415ish with 14.3gr pellet at 69F. Your pistol is screaming!

Maybe you can put your pistol outside for 30 minutes and immediately test it again??? Post results, along with the temperature outside.

Thanks,
Todd

TCooper · #7 Post by **TCooper** » Thu Oct 20, 2005 8:00 pm

Hi ETA,

Maybe the Cr2240 would benefit from a fluted piston or delrin buttons on the piston. These tricks would reduce contact area.

Does the Cr2289 have the same hammer as the Cr2240? If so, then the the 2289 should be effected by temperatures... if the hammer design is a problem.

Thanks,
Todd

ETA · #8 Post by **ETA** » Thu Oct 20, 2005 8:34 pm

TCooper wrote:Hi ETA,

Maybe the Cr2240 would benefit from a fluted piston or delrin buttons on the piston. These tricks would reduce contact area.

Can be done, but not easy.
I thought about doing it some time ago, reducing the weight and contact area of the 22XX hammer. Unfortunately there is a fair bit of obstacles in the design. The trigger relies on the front of the hammer as a stop and needs to be very close. The hammer is a big hunk of harden steel, needs to be annealed to work on.
So day when I get more time.

TCooper wrote: Does the Cr2289 have the same hammer as the Cr2240? If so, then the the 2289 should be effected by temperatures... if the hammer design is a problem.

Thanks,
Todd

The 2289/1377 hammer mechanisms maybe the same, but the principle is a bit different. The whole air charge is dumped at once, so the control of the hammer is not critical, as long as there is enough force to dump the whole charge. The valves in these guns are also smaller, lighter and lightly sprung.

#9 Post by **sniper** » Thu Oct 20, 2005 8:38 pm

Hi Todd,

I always use the RWS Hobby for testing because it's light and cheap. Ok, I will run another test later with 14.3 CR Dome. Usually the 14.3 would cost the fps about 20 - 30.

The 2289 hammer spring is stronger than the 2240, it would blows more co2 and less shots out of a powerlet.

jezX · #10 Post by **jezX** » Thu Oct 20, 2005 11:42 pm

doesn't the tau7 use air ?? . anyway . co2 will drop about 250 psi when put in 60 deg' . this will affect the speed greatly . if you shoot with 850 psi and drop to 600 ,you lose probably 50 fps.
i think my stock 2240 was shooting in the mid 450f/s with wods 14.3gr on a nice day.

ETA · #11 Post by **ETA** » Thu Oct 20, 2005 11:57 pm

jezX wrote:doesn't the tau7 use air ?? . anyway . co2 will drop about 250 psi when put in 60 deg' . this will affect the speed greatly . if you shoot with 850 psi and drop to 600 ,you lose probably 50 fps.
i think my stock 2240 was shooting in the mid 450f/s with wods 14.3gr on a nice day.

The TAU 7 uses CO2.
A well design CO2 or PCP will operate as Todd quoted from Tim at MAC1: "Valve duration is balanced w/ pressure by passing low volumes of high pressure or high volumes of low pressure to yield a nearly flat performance across the pressure spectrum."

The TAU7, and many well designed CO2 and PCP will operate at a very constant velocity over a broad range of pressures. It is worst with unregulated PCPs, at least CO2 is self regulating if you let its temperature stabilized. I guess you can get away with not so good designs with CO2.

#12 Post by **sniper** » Fri Oct 21, 2005 4:06 pm

14.3 gr. CR Dome - 436.3, 438.0, 444.8, 435.5, 432.0, 434.1, 434.4, 436.7, 436.0, 434.7.

Average ft.lbs = 6.04 ft.lbs

Hobby 11.9gr = 6.77 ft.lbs

razpizdiay · #13 Post by **razpizdiay** » Fri Oct 21, 2005 4:48 pm

ah, that makes sense,

since my 2240 was shooting at around 440 stock (with 14.3's). got to get used to the fact that you use 11.9gr's.
by the way, where do you buy them? from D&L? is there a store in toronto that sells them?

#14 Post by **sniper** » Fri Oct 21, 2005 5:11 pm

razpizdiay wrote:ah, that makes sense,

since my 2240 was shooting at around 440 stock (with 14.3's). got to get used to the fact that you use 11.9gr's.
by the way, where do you buy them? from D&L? is there a store in toronto that sells them?

ah ... you want your gun to go wild on fps, use RWS Hobby.
Yes, D&L has them for $9.25, AL's gunshop in Hamilton $8.95, they're 500/tin, if you want some I could get them for you from AL's. Everytime I go there I pick up at least 5 tins. Now I got over 20 tins in stock.

razpizdiay · #15 Post by **razpizdiay** » Fri Oct 21, 2005 5:47 pm

$9 for a tin? i remember you mentioning that you use them because they are cheap... i figure there are 250 in a tin... thats far away from being cheap considering the fact that crosmans are <$4 for a tin.

well, i will just include a couple of tins in my next D&L order (i probably am going to get another steel breech).

thanks for the proposition though