Finding the BC on Cast Bullets

[Ellisace]

I'd like to get into some long range shooting with the 45-70 (300-400 yards) but unfortunately I don't have the space to shoot that far yet. I'm planning on taking a shooting expedition sometime this Spring.

In the mean time I'd like to find out what the BC is on some of the bullets i'll be shooting (a 405 from Oregon Trail and 500 and 730 from Mattsbullets). By goal is to get some ball park numbers so when I get out in the field I'll hopefully get on target faster. Any advice?

[Yodogsandman]

Welcome to the forum!

Ask the manufacturer or look in their advertising. They're the only ones that know what molds they use.

[flyingrhino]

Take a look at this.
http://tmtpages.com/calcbc/calcbc.htm

[OS OK]

I see BC's listed here, guess you could get an estimate by comparison..http://leeprecision.com/bullet-casting/hand-gun-bullet-molds/

[Scharfschuetze]

For the 405 grain OT boolit, it's a BC of about: .300

Maybe slightly less, but if use that figure, you'll be pretty close out to several hundred yards.

I don't know what your velocity goal is, but at 1,300 fps you should be looking at a trajectory of about:

100 to 200 yards: + 12 or 13 MOA
100 to 300 yards: + 31 or 32 MOA
100 to 400 yards: + 61 or 63 MOA

I use that boolit on occasion in Trapdoor Springfields (Replica and Original) with a duplication of the US Army's infantry load at 1,300 fps. It shoots pretty well.

For my cast boolit to duplicate the Frankford Arsenal loads of the US Army I use Lyman's 457193, a plain base design sized to .460."

Have fun on that shooting expedition. I make one or two of those a year back to the Rocky Mountain States.

[CastingFool]

I had the same question so I looked online, found a formula. May be the same one FlyingRhino posted.

[country gent]

The most accurate way to get good BCs is to figure them yourself to your load and actuall velocity. You need velocity at 2 diffrent ranges muzzle and 100-200yds farther is better, perferably of the same shot. The Lab Radar chronograph makes this easy as it can be set to give readings from muzzle corrected to 200yds in increments. There are programs online that allow these numbers to be used to actually calculate the BC and drop tables. Keep in mind BCs do change a little with velocity, Hieght above sea level, atmospheric conditions. 2 chronographs set up one at 10 ft and the other at 200yds giving the velocites from each shot at each distance shows the velocity loss and allows the bc to be figured very accuratly. It takes some time and work but will give you very accurate drop and winfd tables

[flyingrhino]

Using LabRadar you can get multiple downrange velocities. I use mine to calculate BC's.

[Tom Myers]

I'd like to get into some long range shooting with the 45-70 (300-400 yards) but unfortunately I don't have the space to shoot that far yet. I'm planning on taking a shooting expedition sometime this Spring.

In the mean time I'd like to find out what the BC is on some of the bullets i'll be shooting (a 405 from Oregon Trail and 500 and 730 from Mattsbullets). By goal is to get some ball park numbers so when I get out in the field I'll hopefully get on target faster. Any advice?

This Ballistic Coefficient Estimating software works quite well. You can learn more about the program at this link.

Precision G1 Ballistic Coefficient Software (http://tmtpages.com/cast_bc.htm)

Hope this helps.




http://tmtpages.com/balimg/cast_bc_mod.gif



http://tmtpages.com/balimg/cast_bc_calc.gif


http://tmtpages.com/balimg/castbc_secant.gif

[Goober]

Just be cautious to choose the right 'standard' as G1 is not a good comparison for typical long range bullets. G7 will have a much close drag profile across all velocities.

Depends on the bullet profile you are measuring.


This Ballistic Coefficient Estimating software works quite well. You can learn more about the program at this link.

Precision G1 Ballistic Coefficient Software (http://tmtpages.com/cast_bc.htm)

Hope this helps.




http://tmtpages.com/balimg/cast_bc_mod.gif



http://tmtpages.com/balimg/cast_bc_calc.gif


http://tmtpages.com/balimg/castbc_secant.gif