I could use some help with BC values on 38-55 and 32-20

[D-gunner]

I am currently shooting Jamison 32-20 Win 115 Grain RNFP....... AND,,,,,,,, 38-55 Win 255 Grain RNFP. They are not able to tell me the Ballistic coefficients of these rounds. Can anyone out there help me with these numbers?

[Larry Gibson]

A profile picture of the bullets would help?

Larry Gibson

[Norbrat]

Put your bullet profiles in here http://tmtpages.com/calcbc/calcbc.htm

[D-gunner]

198034

[Larry Gibson]

I'd use a BC of .15 on the 32-20 bullet and a BC of .27 on the 38-55 bullet.

Larry Gibson

[Larry Gibson]

Put your bullet profiles in here http://tmtpages.com/calcbc/calcbc.htm

That calculator works fairly well with jacketed bullets. However, most all BC calculators as such always give a higher BC with cast bullets than they actually pan out at. I measure BCs; the M43 Oehler PBL measures time of flight between muzzle screens and screens in front of the target at 100 yards. The "calculators" do not take into account the turbulence/drag created by the lube grooves. I've not found any measured BC of a cast bullet be the same as calculated. The measured BCs are always a bit lower.

Larry Gibson

[country gent]

BCs arnt a solid thing either as they do change for the same bullet slightly with velocities ranges. I would think Larry G's are pretty close on my guess. I have the Lab Radar chronograph and it gives 5 readings down range to work with figuring BCs. It is interesting to see the velocity drop over 200 yds in increments to the target.

[D-gunner]

Thanks Larry! This will really help me out. Maybe with some study I can learn the charts.


I'd use a BC of .15 on the 32-20 bullet and a BC of .27 on the 38-55 bullet.

Larry Gibson

[lotech]

Lyman's books have BC's & depictions of various cast & jacketed bullets.