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Barry McGee's Custom 2300

Cothrane stainless tube, left handed breech, power adjuster,
Lothar 10" barrel, H.P.A.sports co2 cap, Clague ldc,1701 trigger group,
Stace trigger, Rick Andres grips and a Mueller quick shot reflex sight.

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Some old data of interest - 600+ FPE from 12 gr. CO2

June 11 2012 at 10:18 PM
rsterne  (Login rsterne)
Crosman Forum Member
from IP address 66.244.241.34

A few years ago I built a 1750 Carbine.... I used an 18" barrel in .177 cal, Crosman steel breech, and a Dual Power Hammer which featured two cocking positions plus a built in RVA.... After a bit of playing around, I found that I could achieve a large measure of self-regulation in the valve using the low power setting by adjusting the RVA.... What I mean is, that it was relatively insenstive to temperature.... Here are the results at the RVA setting with the best balance, at three different temperatures.... JSB 7.8 gr. Express pellets were used....

[IMG][linked image][/IMG]

Note that on high power, the velocity drops with temperature, as expected.... However, on low power, the velocity is pretty constant over nearly a 30*F temperature range.... In fact, the velocity is slightly lower at 75*F than at lower temperatures.... What DOES change is the shot count.... At 75*F, I achieved over 600 FPE from a single 12 gr. CO2 powerlet.... Here is the hammer....

[IMG][linked image][/IMG]

and here is a photo of the completed Carbine....

[IMG][linked image][/IMG]

This shows the adjustment range of the RVA with both power settings.... Note how the velocity curves cross over at about Low-Power 8 or 9.... That is the "self-regulating" range....

[IMG][linked image][/IMG]

and here are some shot strings at various settings.... Note how the average velocity is higher at High-Power 4 than flat out.... and 50% more shots to boot....

[IMG][linked image][/IMG]

Anyway, I just thought you might be interested.... This was pretty much my only serious CO2 gun.... It ended up having the DPH removed, the hammer spring clipped, and is tuned for about 120 shots (70*F) at just under 500 fps as my Canadian-legal indoor target gun....

Bob


    
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 11, 2012 10:24 PM


 
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CO222
(Login CO222)
Crosman Forum Member
118.149.96.66

Congrats, a new record? Very few have made 550,

June 11 2012, 11:42 PM 

search "horsepower second" to see the other contestants. Very well done.

 
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Lon
(Login bigbore)
Crosman Forum Member
108.132.154.44

475 fpe was the best string I could find...

June 12 2012, 12:34 AM 

although that was a 14" barrel. I think I've done better but this was all I could find right now.

Nice work![linked image]

[linked image]

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
98.69.198.150

Very impressive, Bob - especially in .177! 552 is the best I've done, and...

June 12 2012, 8:39 AM 

...that was aided by a much bigger bore volume (.22) and probably more advantage yet from tandem cartridges.

[linked image]

http://www.network54.com/Forum/79537/message/1280101832/110+shots+from+24gms+of+CO2+---+12fpe+QB78+beats+Horsepower-second+-+12gms+efficiency+mark

Congratulations!

Steve

 
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rsterne
(Login rsterne)
Crosman Forum Member
66.244.241.34

I didn't know it was a record!....

June 12 2012, 9:24 AM 

but that's pretty cool.... I've never tried the same thing in .22 cal but in theory there should be a bit more total FPE hiding in there....

And here I thought the coolest part was that it was self-regulating over a wide temperature range....

Bob

PS, I shot two shots per minute....


    
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 12, 2012 9:29 AM


 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
98.69.198.150

CO2 self-regulation is indeed "cool" (no pun) but often lost....

June 12 2012, 9:31 AM 

...in the enthusiasm for over-springing our CO2 hammers to take max advantage of warm weather, but then have to bundle them off to storage when the weather gets cool.

There are alternatives...

http://www.network54.com/Forum/79537/message/1297468401/CO2+-+30F+to+80F+-+530fps+average+%2B--23fps+stdev

Steve

 
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rsterne
(Login rsterne)
Crosman Forum Member
66.244.241.34

Yes, mild CO2 tunes have advantages....

June 12 2012, 10:29 AM 

I like the looks of your velocity vs. temperature graph in that thread.... 460ish to 560ish between 26*F and 86*F is perfectly usuable.... I didn't explore as wide a temperature range, but the part I did work on showed a similar velocity trend to your experiments.... definitely on the top of the "sweet spot"....

It's interesting that you used a heavy striker with an HDD, whereas I just used a light striker, small travel, and light preload.... and yet we achieved similar results.... Any ideas how you could achieve self-regulation and double the FPE? (other than by increasing the caliber).... It's curious that we are both in the 500 fps range even though in different calibers....

Bob

 
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airgunandy
(Login airgunandy)
Crosman Forum Member
206.208.93.60

Re: Yes, mild CO2 tunes have advantages....

June 12 2012, 10:58 AM 

My oldest son has tuned his Sheridan paint ball markers (single 12 gr powered, similar to Benji EB series, but .68 caliber with a repeater mech) so they still work well in cold weather. He seldom plays paintball in sub-freezing weather, but 40 degrees doesn't seem to bother his shooting or the guns'. Not sure what paintballs weigh, but it would seem to need more oomph than a .22 pellet, although to be legal he has to keep it around 300 fps. I believe he uses a lightened striker and non-stock springs.

I plink, therefore I am.

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
98.69.198.150

Not just mild tunes - low pressure tunes. The logic behind the heavy hammer is...

June 12 2012, 11:13 AM 

...the notion it's hammer momentum that determines valve duration and gas volume release, but hammer kinetic energy that determines the pressure of maximum volume. Therefore, in order to get a velocity "bell curve" centered at relatively low pressure (a.k.a., for CO2, low temperature) you need a high ratio of momentum to energy.

And the way to get that while still retaining useful muzzle energy, since Momentum = (2 x Mass x Energy)1/2, is to increase hammer mass while decreasing hammer spring energy.

Steve


    
This message has been edited by pneuguy from IP address 98.69.198.150 on Jun 12, 2012 11:16 AM


 
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SteveV
(Login stevevines)
Crosman Forum Member
68.52.174.240

Pardon me for pointing out the obvious, but don't you mean 600 fps?

June 12 2012, 11:02 AM 

Seems that some of us are playing fast & loose with our terminology lol? 600 foot pounds of muzzle energy from a co2 pistol?








Vines

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
98.69.198.150

Nope - FPE. Bob is referring to the sum of the energy of all the shots he got...

June 12 2012, 11:15 AM 

...from one charge of gas.

Steve

 
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SteveV
(Login stevevines)
Crosman Forum Member
68.52.174.240

Okay, now I get it....

June 12 2012, 11:50 AM 


 
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Curt
(Login curt44319)
Crosman Forum Member
69.221.167.6

Re: Nope - FPE. Bob is referring to the sum of the energy of all the shots he got...

June 13 2012, 2:07 PM 

Which is actually quite high !
Approaching 30% of the theoretical maximum in the powerlet !

http://www.network54.com/Forum/275684/message/1335737040/

 
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Rich D.
(Login Arkmaker)
Crosman Forum Member
74.170.102.119

Holy Cow!!

June 12 2012, 11:39 AM 

and I am looking to get just half that (60 shots) at 425/450 fps from one cart!!! Man, I have a long way to go! You the man when it comes to Co2, there is no denying that!!!
Rich

 
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Larry
(Login breakfastchef)
Crosman Forum Member
75.139.94.168

I Meant To Tell You About This Thread

June 12 2012, 4:51 PM 

The information fits in perfectly with your 22xx project. But now, with a 1701P in hand, you are likely not going to be messing much with the 22x.

 
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Rich D.
(Login Arkmaker)
Crosman Forum Member
74.170.102.119

Oh yes, I will!!! I have been wanting to do that experiment for the longest time!!

June 13 2012, 8:39 AM 


 
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Z731
(Login Z731)
Crosman Forum Member
108.57.24.28

RVA and DPH ?

June 12 2012, 7:38 PM 

I give up what are they short for ?

 
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rsterne
(Login rsterne)
Crosman Forum Member
66.244.241.34

Rear Velocity Adjuster and Dual Power Hammer.... n.t.

June 12 2012, 7:56 PM 

Bob

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
98.69.198.150

And let's not forget the ever-popular GOBJ.

June 12 2012, 8:47 PM 

Gratuitous Opaque Bewildering Jargon. happy.gif

Steve

 
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dan house
(Login dan_house)
Crosman Forum Member
71.210.114.92

hehe Im a computer guy

June 12 2012, 10:45 PM 

got no room to talk about TLAs and FLAs......




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