Many calculate, estimate, and guesstimate bullet B.C. but the only way to know for sure is by measuring them over extended ranges, Today that is done with Doppler radar. B.C. varies continuously with velocity. A bullet does not have a single B.C. Anyone who has read Bryan Litz's books of long range shooting and seen how much discrepancy exists between published B.C. and real world measured B.C. will never believe advertised B.C. again.
Bagtic the only problem is, the Doppler Radar is seldom used for the bullets we shoot with black powder for accurate data.
I'd b surprised if I was not 0.5 or better. When using the JBM Ballistics software for the Money bullet launched at 1350 fps I found that using 0.5 predicted significantly higher sight settings than I experienced at distance. ( Part of that is because I think the G1 drag curve is not a good approximation at the lower speeds experienced at the greater distances ). I imagine that the prolate is the same or better with respect to aerodynamics.Originally Posted by kokomokid
Chris.
FWIW, a buddy of mine is switching from grease groove money bullets to a 504 gr Prolate in his .45-70. He has found that sight elevations from a 200 yd zero to reach 800 is much less with the latter bullet. I was surprised because I have never measured super high BCs for my bullets (always done over 100 yds), but that is in comparison to internet BCs which are, I believe, vastly, vastly inflated by a few folks. I don't think a prolate will be over .55 BC at best. Regardless, it will simply shoot championship accuracy.
Brent
I've never tried measuring the BC using two chronographs. I've just been using the JBM ballistics software and adjusting the BC numbers until they "best fit" the sight settings, while factoring in weather conditions. There is likely significant uncertainty in he numbers, but I've found that 0.5 was a pretty decent fit for my 535gr GG Money bullets IIRC, but with the PP bullets to 800m, the software predicted 10 minute higher sight settings than I actually needed.
I'm guessing that the prolate bullet might be a touch better, but only because my .38 PP bullet needs less elevation to go from 100m to 200m than any of my .45 cal Money bullets shot at similar speeds. That again is a pretty crude guess though
In the end, I bet that in real world conditions with top class shooters, that no one would notice a practical advantage with one over the other. Probably they'd both work well enough to win when used by someone better than me
Chris.
One thing none of the ballistic calculators can take into account is mirage and wind, either or both can change the elevation setting needed.
It's not uncommon for a paper patched slick to need less elevation on a sight staff than a grease groove bullet in the same cartridge. It can be anywhere from a few minutes to as many as 15-20 minutes less for a paper patched bullet.
Long range rules, the rest drool.
Don, it' pretty easy nowadays to make a ballistic calculator that takes into account the wind. I wrote one ( it's actually a work in progress still ) and it'll allow you to modify the wind at any point in the trajectory as many times as you like. Nowadays it's no big deal to recompute everything 10,000 times a second if you like. How closely you can get it to match reality is another thing of course
I wrote it to see if I could get better predicted sight settings for my rifles than I get with the JBM software, and for curiosities sake. I've been toying with making it into a bpcr computer game, but that's a much bigger job.
Chris.
Chris I don't know which program Dick Savage used to use, but he would run all the data thru the thing, show up at the gong match in Alliance and the darn thing would be awfully close. I've used the one Hornady has on their web pages, and it doesn't do to bad of a job.
But still none of that will speak to us like the actual trigger time.
Long range rules, the rest drool.
Yeah that's a fact. It'll be a long time coming before anyone wins a black powder match with a computer
Chris, what language are you writing your code in?
Brent I'm using C#, although I might switch to C++.
The code I'm writing is not very sophisticated, I'm just integrating the equations of motion from McCoy's book using an RK4 integrator and the G1 drag tables he includes. It's just a 3 DOF simulation right now but I will add spin drift to it at some point in time when I figure that part out.
My plan is to add some code to perturb the G1 drag curve to see how well I can make it match my sight settings. I have a feeling that it's probably just a matter of reducing the drag a bit at the lower velocities. I haven't shot enough at longer ranges to have a lot of data though.
Chris.
that sounds like fun. I have been teaching myself Python as a poor alternative to Pascal. I'm beginning to think I should have just thrown in the towel and gone on to C++.
the problem with data from longer ranges (and even some sorter ones) is that there are almost certainly several different winds between you and the target. Most of them, you have no idea are even there. So, the variance in the data are hard to ascribe to anything in particular.
I'm about to head out to Oak Ridge for a match. It has some especially interesting winds in that the bullet flies over a gully and is way above the flags when shooting from the 1000 yd line. Pretty much a guess what the wind is up there, but at least it is probably less turbulent.
good luck with the code writing.
Python is a neat, but strange language. I used it maybe 15 years ago for a little bit. It was definitely interesting. Nowadays for small applications C# might be the best way to go, although C++ has a definite performance advantage depending on circumstance.
I know what you mean regarding unseen winds. The 800m gong at Heffley Creek is more than 200 feet higher than the shooting line and we have some very interesting terrain that usually causes the wind flags to point in opposite directions in the afternoons. It's anyone's guess what's happening way above the flags, but I'm sure you are correct about less turbulence. In that case I bet there is an advantage to the guy who can shoot the fastest
Chris.
Ah yes, there is something to be said for breaking a shot fast, but there is a lot more to be said for breaking a shot on target. I don't muff many, darn few, but I did muff one the last time I shot long range nationals. It would have been a 100-5x for national record but I pulled it out into the 8 ring at 3 o'clock and told my spotter so before the bullet arrived at the target.
The way it goes. This coming weekend, I'll be shooting the Long Range game with muzzleloaders - really a combined, mid/long range match, 200,300, 600, 1000. It is a "call your own wind" game and one that is slow just because it is with muzzleloaders. Last year I had 90-5x in the bag at 200 with the last shot to go. I took an extra couple seconds and shot a 9 at 9. It was a wind that came by while I was in the gun. My spotter and one other guy saw it and they knew what would happen. Too bad, they said that would have been a record if I had taken a 10 or better with it.
I'm a slow shot, but I think it works for me.
Brent.
There are a lot of last shot muff shots if one likes to admit it or not. I had a last shot muff shot at the Quigley when I shot a 41 that would have place me above the 13th place I finished at
I will be shooting at Effingham next weekend if I can get away.
These look like shooters:
KAL 45 PP 1.55 Elliptical_zpsm8ibmf9j by Sharps45 2 7/8, on Flickr
The one on the right should work, but it is dangerous to judge a bullet's potential from a picture. In the end, it is the mathematics that count.
They look like my .44's.
The one on the left is the KAL .432 505 gr elliptical and the one on the right is my Brooks mould .433 485 gr Prolate.
Hey Sharpsman, What twist are you shooting a 1.55" bullet?
Chill Wills
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