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

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

Joined: February 17th, 2010, 3:30 am

June 12th, 2012, 4:18 am #1

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]

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]

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

[/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]

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]

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
Last edited by rsterne on June 12th, 2012, 4:24 am, edited 1 time in total.
Quote
Like
Share

Joined: June 5th, 2006, 12:49 am

June 12th, 2012, 5:42 am #2

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

Joined: August 16th, 2004, 7:32 am

June 12th, 2012, 6:34 am #3

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]

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]

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

[/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]

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]

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

Nice work!

Quote
Like
Share

Joined: November 28th, 2002, 6:26 pm

June 12th, 2012, 2:39 pm #4

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]

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]

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

[/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]

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]

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



http://www.network54.com/Forum/79537/me ... iency+mark

Congratulations!

Steve
Quote
Like
Share

Joined: February 17th, 2010, 3:30 am

June 12th, 2012, 3:24 pm #5

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....
Last edited by rsterne on June 12th, 2012, 3:29 pm, edited 1 time in total.
Quote
Like
Share

Joined: November 28th, 2002, 6:26 pm

June 12th, 2012, 3:31 pm #6

...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/me ... 3fps+stdev

Steve
Quote
Like
Share

Joined: February 17th, 2010, 3:30 am

June 12th, 2012, 4:29 pm #7

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
Quote
Like
Share

Joined: February 9th, 2006, 10:35 pm

June 12th, 2012, 4:58 pm #8

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.
Quote
Like
Share

Joined: October 14th, 2006, 12:30 am

June 12th, 2012, 5:02 pm #9

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]

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]

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

[/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]

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]

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








Vines
Quote
Like
Share

Joined: November 28th, 2002, 6:26 pm

June 12th, 2012, 5:13 pm #10

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
...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
Last edited by pneuguy on June 12th, 2012, 5:16 pm, edited 1 time in total.
Quote
Like
Share