wunnerin

[tuckerdog]

where can i find bc's( ballistic coefficents) for cast boolit designs. I know these will be approximates

[Crawdaddy]

Leeprecision.com in their mold section

[tuckerdog]

looked, under what heading

[JSnover]

Under Bulet Casting... Select rifle or pistol, then single or double cavity. When the mold page opens it will be the top bold number under each image.

[tuckerdog]

DUH! I guess I never noticed. Thanks
It's true what they say.. us redheads are just blonds with high blood pressure

[darkroommike]

Lyman Reloading Handbook 49 has the sectional density and ballistic coefficient listed for each bullet type load data.

[JohnH]

In all this I'm not chastising, just sharing my experience...

The problem with ballistic coefficients and the reason why Sierra quit publishing them is that BC changes as the velocity changes. As well, elevation above sea level plays a lot more havoc than one might expect. I live in Alabama and shoot Pdog (prarrie dog) in Oklahoma. My elevation is 1600 fps and it is between 4000 and 4500 in OK. (IIRC) I can zero here at 200 and be pdog dead on at 300 out there. Here I wouldn't even touch the animal with a 200 zero. Sea level is important in the equation as this is what all the data is generated at. BC as we know it is based on work a man named Krupp developed. As the bullet shape veers from the standards Krupp set out, so does the actual flight of the bullet as compared to what the BC describes. VLD bullets (the Scirocco is an example) outperform the Krupp standards noticably. (Yes I know that's not a boolit)

The Lyman #47 manual starting at page 176 gives BC data for many of their boolits. As an example of what I'm saying, the 31141 is shown at velocities of 2200 and 1600 fps. The BC is shown as being .220 at high velocity, .250 at intermediate velocity and .280 at low velocity. The 311284 is shown at velocities of 1800-1400 fps and BC is shown as being .332 .331 and .335 for high, intermediate and low velocity. The 311299 is shown at velocities of 1800-1400 and the BC is given as being .377 .358 and .390 at high intermediate and low velocity. Spreads for the 22 calibers are over .040 over a 1000 fps test velocity range.

I discovered how horrid all this is about 4 years ago when I loaded my 25-06 with WC860 and the Speer 120 grainers for hunting deer that season. I clocked the loads at 2700 fps and then went to www.realguns.com and ran the ballistic program on the bullet and the known velocity. Shooting at a doe at a lasered 220 yards, I racked up 3 misses. The following year I took a doe at the same spot using a 243 with a 100 grain Remington Coreloct... one shot. The difference? Going to a two hundred yard range and sighting it in at that range. I learned a lot out in OK the summer between those two hunts.

Sierra says it well in one of their manuals, a person shooting pdogs will learn more in a few days about shooting than many deer hunters learn in a life time. Up untill that experience I would have arm chaired argued about BC till the sun burned out. Today, I still play with BC numbers and ballistic charts and programs but in the end if I want to know what a boolit is doing, I go shoot it at the range at which I want to know what is happening.

[tuckerdog]

JohnH... I agree with you. BC is only a reference to use as a starting point. The real deal is in burning lots of powder. I've never used bc with boolits only jacketed and thought it would be fun to play with. I am constantly (to my wifes agrrivation) finding different things to tinker and mess with

[JohnH]

Forgot to add that if you got a Lyman mold and want the BC, give me the number. If it's in the chart I'll let ya know.