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PostPosted: Thu Jan 16, 2014 9:54 pm 
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Location: Central West River Nova Scotia
Pretty awesome number,s Bob.quite humbling.

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PostPosted: Fri Jan 17, 2014 12:05 am 
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Location: Coalmont BC
It's pretty amazing what you can do with an 18" barrel, in .177 cal, shooting 7.8 gr. pellets.... When I built that gun (which I still have) I wasn't going after any records, in fact I didn't know there was such a thing.... I was trying to get a CO2 gun to "self-regulate" like a PCP does, so that the velocity was relatively constant over a wide range of temperatures.... You can see how well I accomplished that, the three horizontal strings are at 46*F, 62*F and 75*F, all that really changes is the shot count, many more shots at the higher temperature.... I fact, the velocity was higher at 46*F than at 75*F.... Although it's not on that graph, I also tested the gun right out of the fridge, at 35*F, and the velocity was nearly the same as at 75*F.... but "only" about 70-80 shots.... I had to keep putting it back in the fridge to keep it cold, so never got a completely accurate count....

The hammer I was using was made by ustilago, called a "Dual Power Hammer", and it looked like this....

Image

As you can see, it has two cocking positions, the one of the left produces the same stroke as a stock Crosman hammer, and the other one has only about half the travel.... There is a built in RVA.... The previous graph shows the normal behaviour of a 22XX when using the "high power" position, the short curves on the upper left, at the same three temperatures.... Those shots were all done at power level "9", and on the graph below are the velocities for the other settings.... What I noticed was that the 45*F and 68*F curves crossed over at "Low Power 9", so that's how I discovered the ability to have a CO2 gun self-regulate....

Image

After I accomplished what I set out to do and published the results here on the CAF, one of the other members told me that I had broken Steve in NC's 552 FPE record on a single 12 gr. C2 cartridge.... pretty much a bonus, as all I was interested in was getting a CO2 gun that wasn't sensitive to temperature....

Image

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Jan 17, 2014 10:19 am 
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Hi Bob,

That hammer looks like it has a full length spring guide - where does it go during the cocking stroke? Is there room for it to back up into the threaded brass velocity adjuster?


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PostPosted: Fri Jan 17, 2014 11:57 am 
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The hammer doesn't use the cocking pin, it is a rear cocking design.... You pull on the round knob, which is threaded onto the rod / spring guide to pull the hammer back, to either the first (low power) or second (high power) notch.... All the bolt does is load the pellet, it no longer cocks the gun.... When the hammer is installed, you can see the rod, as in the lower photo of the gun, even when the gun isn't cocked....

Joe, I apologize for high-jacking your thread, but I was getting PMs about this stuff.... which started as a response to your question about number of shots per cartridge....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Last edited by rsterne on Fri Jan 17, 2014 12:57 pm, edited 1 time in total.

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PostPosted: Fri Jan 17, 2014 12:33 pm 
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Location: Central West River Nova Scotia
rsterne wrote:
The hammer doesn't use the cocking pin, it is a rear cocking design.... You pull on the round knob, which is threaded onto the rod / spring guide to pull the hammer back, to either the first (low power) or sedond (high power) notch.... All the bolt does is load the pellet, it no longer cocks the gun.... When the hammer is installed, you can see the rod, as in the lower photo of the gun, even when the gun isn't cocked....

Joe, I apologize for high-jacking your thread, but I was getting PMs about this stuff.... which started as a response to your question about number of shots per cartridge....

Bob

No problem Bob. Glad to nkow more about the 2240 and anything else you have to say.

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