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?
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?
A profile picture of the bullets would help?
Larry Gibson
Put your bullet profiles in here http://tmtpages.com/calcbc/calcbc.htm
I'd use a BC of .15 on the 32-20 bullet and a BC of .27 on the 38-55 bullet.
Larry Gibson
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
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.
Lyman's books have BC's & depictions of various cast & jacketed bullets.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |