I don't see any harm or anything odd about just wanting to know from experimental testing and validation. If one never does any hands on experimenting, just reading some one else's test reports, what fun is that?
I don't see any harm or anything odd about just wanting to know from experimental testing and validation. If one never does any hands on experimenting, just reading some one else's test reports, what fun is that?
My Anchor is holding fast!
Thank you for your comments, and also in the other post. Your comments did not however clarify for me if ballistic coefficient is really determined experimentally and then the impact of the various factors estimated through analysis, or if it is rather calculated and any real world deviance attributed to other factors. Specifically you say that ballistic coefficient is the sectional density divided by the coefficient of form...and I understand that the sectional density can be calculated, but how is the coefficient of form determined?
Actually the BC is derived from a comparison of the TOF (Time Of Flights velocity retardation rate; computed or measured) of the bullet to the TOF retardation of the "standard projectile" (most often the "G1") by division. Most BCs we find these days are based on computer models used in a computer program. Those often times, if not most of the time, are higher than actual measured BCs based on actual TOF.
I will find it interesting to see what the OP's radar actually measures the BCs at. I also measure BCs via the M43 Oehler by measuring the actual TOF of the bullets across 100 yards. Just two days ago I shot the 30 XCB bullet at 2900 fps out at 600 yards. Using the actual measured BC the Applied Ballistics program's elevation from a 100 to 600 yard zero was spot on. Using the computer generated BC in that program the elevation would have not have been correct. I agree the OP's experiment should prove interesting and informative.
Larry Gibson
“Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
― Nikola Tesla
I think that it is quite interesting to compare the apples and oranges. Look at the conversation that it has started.
Powder, load and platform shouldn’t change the result of the stated goal. Speed will be measured at both ends.
Still looking forward to results
I want to know how the chorno's were setup. At 325 yards you're going to have about 10 to 20 feet of drop and at least a couple feet of wind drift to deal with.
Why 325 yards? Wouldn't the BC calculations from 50 or 100 yards yield the same results.
I am not sure why that range. I do know the messy bear commonly shoots at a steel ram outside his front door that is about that distance. I would assume one crony at 10-12 feet. As is typically how he sets things up. And the second one sits behind a steel plate with a hole cut into it.
I do know from looking at the plate that it has proven to be necessary. Not “every”shot at that range might make the 10” hole
I see a few of us (in general) here have a hard time with someone experimenting like this. Who cares if it's been done before, even a million times. Who cares. I'll sit back and "eat my popcorn" and appreciate the time, effort, and risk it took someone else to gather data like this. No need to belittle. Fun!!
Dang right!
This should rank right up there with our chronographing revolvers with no barrel test! Pointless, but dang fun and interesting!
JBinMN,
No problem! Cheers!!
BCs also change in velocity ranges. Mass of a projectile carries energy and velocity, Also sub sonic and super sonic affect velocity loss differently. Heres a good comparison to look at 308 762 nato in most loads 168 grn bt at 2650-2700 fps top range is around 1200yds a 50 bmg 700 grn bt at 2600 fps range is out to almost 3000 yds. These are 2 bullets close in form and velocity with the major difference being weight.
If you think you need an excuse to get out and so some shooting, its as good a reason as any. Or if you are just after iformation you can read about it.
https://en.wikipedia.org/wiki/Ballistic_coefficient
http://www.sellier-bellot.cz/en/prod...t-calculation/
Have mercy.
A haw, haw, haw, haw, a haw.
A haw, haw, haw
Jim,
Yes, the Coefficient of Form for the G[1, 2, 5, 6, 8 & L] and Krupp drag tables can be calculated.
The Coefficient of Form for the G7 series is best determined by measuring real world performance data. However the G7 Form Factor can be approximated by calculating a G1 factor and then dividing that value by 2. (The G7 is based on a standardized boat tail bullet with a 10 caliber secant ogive and a diameter of 0.50" whereas the G series is base on a projectile with a 1.00" diameter.)
As described in the link to the Form Factor in my previous post, the Coefficient of Form, or Form Factor (for the G? series of drag tables) may be calculated for pointed, jacketed bullets, with a tangent ogive nose profile, using a function of the ogive radius expressed in calibers.
*****
The basic function used to calculate the Coefficient of Form:
R = the radius of a tangential ogive divided by the diameter of the ogive base.
Form Factor = 2 / R * Square root of [ ( 4 * R - 1 ) / 7 ]
Proportional form factor modifications are required for any variation in meplate diameter.
*****
The radius of a tangential ogive can easily be calculated as described in the link to the Ogive Radius
*******
The function used to calculate the length of a tangential ogive radius.
NL = length of the curved portion of the nose.
D = The diameter of the nose where the curved portion begins.
T = The diameter of the tip or meplate, whether rounded or flat.
L = The length, in inches, of the curve radius.
L = ( NL * NL ) / ( D - T ) + ( D - T ) /4
*******
As also described in the link to the Form Factor, using a highly modified form of the function used for pointed, jacketed bullets, the Form Factor for cast bullets with meplate values that are less than 50% of nose diameter, the Coefficient of Form may be reasonably estimated.
However, when calculating trajectory values for bullets with wide meplates [+ 50%], simply using the Sectional Density Value in place of the Ballistic Coefficient value will usually return a more realistic approximation of the trajectory.
As has been stated many times in this thread. A reliable ballistic coefficient value must be physically determined using actual trajectory values and,
as the title " G1 Ballistic Coefficient Estimator " implys, if trajectory values are not available or can not be determined, they can be closely estimated and used for comparison purposes when calculating the external and terminal ballistics values for a particular bullet design.
Hope this helps.
Last edited by Tom Myers; 03-12-2018 at 10:17 AM.
Respectfully,
Tom Myers
What’s the deal messy bear!? We are all hanging here waiting!
Dang! Had it typed out and timed out! Sorry guys been busy lately.
22- 1176 ave of 5 start velocity. Those 5 at 325 yd - 740 ave.
45- 1170 ave of 5 start velocity. Those 5 at 325 yd- 836 ave.
Messy
Great post Tom. Very cool
Thanks Tom! Yery interesting! I wonder what Lee says the b.c. is on that bullet?
Messy bear,
Lee Lists that Bullet as having a Ballistic Coefficient of 0.210
I acquired that mold some time ago to use in my 45 Long Colt revolver but never got around to trying it. Gonna have to do that this summer.
The only thing I have used it for is to make up a bunch of soft slugs fire-lap my Pedersoli Sharps 45-70. They worked great for that. No more leading.
Your test firing returns a B.C. of 0.1918.
My Cast Bullet Design and Evaluation software estimates a B.C. of 0.1798.
That suggests, to me, that this bullet, with your load, in your firearm is very stable throughout the trajectory.
Good work!
Respectfully,
Tom Myers
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |