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+---- Thread: Bullet BC for 45 cal. (/thread-1878.html)
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Bullet BC for 45 cal. - Eric Johanen - 05-12-2016
Friend is going to work up charts for me using ballistic programs he has and I can provide him with chrono data but have no idea for the ballistic coefficients for bullets we use. Any ideas as to BC for 535 grain Money nose bullets, 545 grain Creedmoor type noses and 540 grain paper patch Money nose bullets. Or a 535 grain Postell nose? Would like to see how the charts compare with actual sight settings I am using for long range shooting.
RE: Bullet BC for 45 cal. - Don McDowell - 05-12-2016
Go to Handloads.com and use the ballistic calculator there, it will give you a rough bc for the bullets.
RE: Bullet BC for 45 cal. - Eric Johanen - 05-12-2016
Thank's Don but almost everything there is archived and will not display...Shows error! Nosed shape for the ballistic calculator just has round nose and I don't think that is close enough for my friend to work with.
RE: Bullet BC for 45 cal. - Don McDowell - 05-12-2016
Hmm haven't looked at that for awhile..
RE: Bullet BC for 45 cal. - Old Jim - 05-12-2016
MLV's book says the 457132 @536gr. = 0.402;
and the Lyman 457125 @520 gr. =0.363;
and the Saeco 745 @534 gr.=0.399
YMMV
Jim
RE: Bullet BC for 45 cal. - bruce moulds - 05-12-2016
eric,
it is next to impossible to calculate b.c. using the various calculators available to us, as they do not take into account the drag due to various nose forms and grease grooves in theit various forms or lack thereof.
I suspect that the mlv figures were derived from shooting with 2 chronographs at closer ranges.
this puts the readings in the highest drag area of the transonic zone of most cartridges, which can lead to lower b.c. readings than for average flight., although correct for the ranges shot.
the best way to establish b.c. has proven to be shooting at 3 or more ranges to establish sight settings.
you will need to know your sight radius to convert to true moa, and the muzzle velocity.
with these figures, you can run jbm ballistics repeatedly trying different g1 b.c. numbers until a trajectory matches yours.
you will need the barometric conditions and elevation above sea level for accurate numbers.
doing this will give some interesting surprises, like how much grooves and rings reduce b.c., with the corresponding increase in wind deflection.
if possible, 3 good ranges are 300, 600, and 900 yards or meters.
this is because good long range bullets are transonic out to about 700 yards, and you will go past this.
keep safe,
bruce.
RE: Bullet BC for 45 cal. - Eric Johanen - 05-13-2016
Thank you Bruce. I can get the elevation numbers over the course of this season at matches I shoot. Rest of the input data should not be too hard to obtain. Thinking about this as a result of the Lodi, WI. Creedmoor I just shot and one of my squad mates was really stumped by the elevation difference switching from a 545 grain creedmoor nose to a 535 grain money bullet nose. His 45-70 needed almost 18 minutes of lower elevation to hit paper at 1000 yards. Did not expect it to be that much so working up a chart will be an interesting project. I think he required 10 minuets change at the 800 yard line.
RE: Bullet BC for 45 cal. - Don McDowell - 05-13-2016
Eric, not sure if Hornady still has their ballistic calculator, but it works out fairly close. But none of them can account for headwind/tailwind, light and mirage.
RE: Bullet BC for 45 cal. - Gunlaker - 05-13-2016
Eric I use the JBM Ballistics software and a BC of .510 for my 535gr PP Money bullet. The numbers were very close to what I used at Byers and Ben Avery. Certainly enough to get me on paper very quickly. The hard part was staying there :-). Like Don said, throw in some interesting conditions and the numbers change pretty quickly anyway.
Interestingly, my first attempt at using JBM Ballistics software at long range was at my first 800m gong shoot. I was shooting nearly the same bullet, a 444540 PP Money out of a .45-110. The JBM software predicted I'd need 10 minutes more elevation than I actually needed. I am not 100% certain why the difference as both bullets fly at nearly the identical speed. Maybe the fact that I use Fg and a lube cookie in the .45-110 minimizes nose upset and results in a higher BC bullet after it exits the muzzle?
Chris.
RE: Bullet BC for 45 cal. - Eric Johanen - 05-13-2016
I think you are right Chris. When using a money bullet nose with my 45-70, 77/78 grains of OE 1.5 and a 20/1 alloy shot very well. Same bullet in my 45-90 with 97/98 grains of OE or Swiss 1.5 not as well. I think there is some bullet slump and when I switched to a 16/1 alloy there was a big improvement. The money bullet nose is sure flatter shooting than a round nose profile like a creedmoor design. From the reports, the elliptical nose also is pretty flat shooting. It will be interesting to see what my friend comes up with after I get him some good data to work with. I know I did not expect almost 80 inches flatter at 800!