I gathered some data today and ran it through an online ballistics calculator. I used this site for the BC calculations: [www.eskimo.com].


1/25/09 BC testing
Patuxent River

28.7 °F 56% 30.35 in (Steady) Partly Cloudy ESE at 2.0 mph 11:51 AM EST

Elevation 105 feet, all shots taken with Prairie III regulated at 3250 PSI

.32 Bishops 94gr
3 yards; 755.3 FPS
42 yards; 661.4 FPS

JBM Ballistic Coefficient (Velocity) Output
Input Data
Near Velocity: 755.3 ft/s Far Velocity: 661.4 ft/s
Distance: 117.0 ft Drag Function: G1

Temperature: 28.7 °F Pressure: 30.35 in Hg
Humidity: 56.0 % Altitude: 105 ft

Std. Atmosphere at Altitude: No Corrected Pressure: No
Calculated Parameters
Atmospheric Density: 0.1 lbs/ft³ Speed of Sound: 1083.4 ft/s
Ballistic Coefficient: 0.042 Time of Flight: 0.165744 s
25 Jan 2009 09:02:00, JBM [http://www.eskimo.com/~jbm]


.32 Falcons 77.2gr
3 yards; 786.7
42 yards 678.7

JBM Ballistic Coefficient (Velocity) Output
Input Data
Near Velocity: 786.7 ft/s Far Velocity: 678.7 ft/s
Distance: 117.0 ft Drag Function: G1

Temperature: 28.7 °F Pressure: 30.35 in Hg
Humidity: 56.0 % Altitude: 105 ft

Std. Atmosphere at Altitude: No Corrected Pressure: No
Calculated Parameters
Atmospheric Density: 0.1 lbs/ft³ Speed of Sound: 1083.4 ft/s
Ballistic Coefficient: 0.038 Time of Flight: 0.160396 s
25 Jan 2009 09:03:28, JBM [http://www.eskimo.com/~jbm]




.32 Cans 114gr
3 yards; 683.7
42 yards; 626.0

JBM Ballistic Coefficient (Velocity) Output
Input Data
Near Velocity: 683.7 ft/s Far Velocity: 626.0 ft/s
Distance: 117.0 ft Drag Function: G1

Temperature: 28.7 °F Pressure: 30.35 in Hg
Humidity: 56.0 % Altitude: 105 ft

Std. Atmosphere at Altitude: No Corrected Pressure: No
Calculated Parameters
Atmospheric Density: 0.1 lbs/ft³ Speed of Sound: 1083.4 ft/s
Ballistic Coefficient: 0.061 Time of Flight: 0.178935 s
25 Jan 2009 09:04:21, JBM [http://www.eskimo.com/~jbm]


.32 Boat tails 112.2gr
3 yards; 692.8
42 yards; 662.6

JBM Ballistic Coefficient (Velocity) Output
Input Data
Near Velocity: 692.8 ft/s Far Velocity: 662.6 ft/s
Distance: 117.0 ft Drag Function: G1

Temperature: 28.7 °F Pressure: 30.35 in Hg
Humidity: 56.0 % Altitude: 105 ft

Std. Atmosphere at Altitude: No Corrected Pressure: No
Calculated Parameters
Atmospheric Density: 0.1 lbs/ft³ Speed of Sound: 1083.4 ft/s
Ballistic Coefficient: 0.122 Time of Flight: 0.172715 s
25 Jan 2009 09:05:04, JBM [http://www.eskimo.com/~jbm]

I used this data in Chairgun to develop some graphs. I have other data telling me what velocity these rounds will fire at higher power settings and it will be interesting to see if the graphs are close to reality. I found that Chairgun is limited to the smaller slugs and also develops different BC values with the same inputs. Given that Chairgun would not keep my environmental data and would not accept heavy weights and did not ask for humidity... I decided to use the JBM values. For the heavier slugs I used Point Blank ballistic software to graph bullet drop. This software is free but is for powder burners so it doesn't offer the resolution that Chairgun does. We need software designed for big bore airguns...

As far as the BC values go: The Falcon came out a little better than I expected as did the Can. The Bishop is right about where I expected it but the Boat Tail really came out great. I'll have to check the Pepper Grinder and Totem Pole on another day.



Edited 1 time(s). Last edit at 01/26/2009 06:15PM by Jerry.

Sweet, thats really getting some hard data on things. I've got a program that figures muzzle energy, but nothing like this.

Jerry,

Good stuff!

Are you trying to one-up me with the data collection Jerry?

Excellent, excellent stuff. It'll be very interesting to see how the BCs of the .32, .45, and .46 Bishops compare.

-- Jim

Interesting reading, Jerry...

Your .32 bullets conserved their energy level very well. Small bore (.177) pellets should lose much more energy, if compared; and especially so, if they'd be light .177 pellets of diabolo type.

BTW, what was/is the mass of each bullet type you used?

Sepeteus,
I just edited my post to include the weight of each of the slugs.

Jim,
If somebody would let me borrow their .45 I might try to do that comparison! What did you use to figure the BC for your slugs?

I used one of the online calcs. I'll have to find it again and post a link.

-- Jim

Nice work Jerry.
Have you had any other feedback on the Raptor BC, to compare with my Chairgun-derived figure of .055?
And got any pics of those various slugs you tested?
Cheers
Neil

Hi Neil,
I've not recieved any other feedback on the Raptors. It is very rare to get any feedback at all much less real data! I'm thankful you did the testing you did. BTW, do you still have the numbers you used back when you tested? If you had the temperature, elevation, barometric pressure and humidity I could run the numbers through the JBM site. I'm suspect of the Chairgun values because that program doesn't ask for all the variables.

I've not posted pictures of the Barnes slugs as the designs are proprietary. The Boat Tail is my design though and I'll share it here:

Note: This slug is fired with the flat end forward and that is the way it was shot to gather the BC data above. It is too short to be shot the other way around in the Prairie or Woodsman. If it were 1/8" to 3/16" longer it might engage the rifling properly with the ogive forward but that will have to wait on another day. This particular slug was cast last night in a quick sesion by me. I see that it has a bad wrinkle in it. A 50 yard slug...

Hi Jerry
I must admit that I didn't get as technical as measuring humidity etc, so you can take it that my measurement is an approximation....though with average temperature/altitude etc figures in place I have had very good results using the Chairgun BC figures for my Falcon; granted that the program does allow for the weight of the small bore pellets but not for big bore.
A good way of determining how well Chairgun performs with big bores will be testing a scope tape created through the program. I have made up one or two and when I finally get back to shooting my .45's I will report on this. In the meantime I have been distracted by the arrival of my new .50 cal, which I will share soon.....
Cheers
Neil

Can't wait to hear about the new .50!

It's now in the Gear Shack, Jerry

WOW jerry, that is some great info. Looks like you put in some hard work and came up with some hard data. Very nice.

Hi Ced,

Thanks for the comment. It really wasn't that much work since I had the gun set-up and ready to shoot already. I just had to get the chrony out and put it on my new tripod. I've been going for a long time without a proper tripod and finally picked one up at WalMart. I'm sure it is not much compared to what photographers use now but this tripod has a bunch of features, seems nice and sturdy and was cheap. That let me take a bunch of shots and then just tote the chrony out to the target wall and repeat the sequence. I'm going to have to check a few more slugs. It should lead to some fun shooting sessions comparing the predicted values with reality. I hope to have at least one slug map out as well as Neil's Falcon. Then I can make a scope knob tape.