Ballistic Coefficient for Kodiak Match .177

[wkoslo]

I can't seem to find the ballistic coefficient for the Beeman Kodiak Match extra heavy .177 cal, 10.65 gr pellet. I see 10.5 gr listed in a variety of online sources but not the heavier pellet. I'm guessing the profile of the pellet has stayed the same, just the wt has changed? Would there be any difference in BC between the two?

 

[Guest]

There would be a difference but it might not be immediately obvious. Temperature, humidity, and pressure, even choke in your barrel can make a difference to the measured BC of a pellet. So Chairgun Pro lists the following:

Beeman Kodiak (10.5) 0.0230
Beeman Kodiak Match (10.5) 0.0240
H&N Barracuda (10.5) 0.0250
H&N Barracuda Match (10.65) 0.0235

I've observed large variations in the third significant digit, sometimes even in the second significant digit, when measuring BC on my range. I would say if you average the above you will have something which is probably about as accurate as you are going to find anywhere else other than on the range with the chronograph on any given day.

 

[wkoslo]

Thanks for the info.

Walt

 

[Guest]

Walt;

I can add that I measured a BC of 0.0203 for the Barracuda Match (10.65 gr) in my D350. That gun pushes them at about 935 fps. That is in the near subsonic range so it might have dragged down the BC a bit, but it probably wouldn't hurt to include that measurement in your average of the above Chairgun data. I make that average 0.0236. The thing is (as I implied) measurements of BC can vary quite a bit with conditions, specific guns, and even different pellet lots. The good news is the drop of a BC of 0.020 at 50 yards computes to -6.5" for my rifle zeroed at 25 yards and a BC of 0.025 computes to a drop of -6.2" for the same muzzle velocity and zero range. We are talking 3/10 of one inch at 50 yards. That ain't much and it tends to be swamped by zeroing errors, range estimation errors, wind estimation errors, etc... A 30 fps increase in muzzle velocity with that pellet, rifle combination has the same effect, drop goes from -6.5 to -6.2 inches. You get the idea. The third decimal place is essentially a crap shoot unless you are shooing indoors, under controlled conditions, from a bench.

Mike

 

[Yrrah]

Oldspook has given a good summary.
This morning Sept 3 in OZ I have taken the time to run some 10.65 gr Barracuda .177 Match past my Labradar radar chronograph from the RAW TM1000 benchrest gun with LW choked barrel. You may notice a trend as the velocity moves down further from Mach1.
Velocities are rounded; 19dC, 987 mB, 65%RH. Range from 0 yards to 23 yards
Vel; BC (average from all data points of approx 2 per yard).
894; .0198
872; .0199
862; .0204
857; .0202
848; .0203
843; .0209
815; .0209
813; .0213
Playing with temperature inputs seems to indicate a BC increase of approx 0.0001 per dC.
# A different barrel and ambient conditions may give other results as most now know.
# There was a trend for the drag coefficient to peak at around 10 to 14 yards then reduce from there. Stability may be best at a longer range so BC average may be higher over a longer range. My research on .25 cal JSB Kings from a BSA barrel indicated average field tested BC still improved to 100 yards and to 200 yards as initial instability damped out. ... Other pellets at other velocities can become unstable beyond 40 to 50 yards and demonstrate spiral flight with deterioration of Cd and BC.

There are rough rules of thumb but no simple answers to simple questions in this game. The more I explore the more fascinating I find it to be. .... Best regards, Harry.