Trying to calculate and print out trajectory information for the ammunition we use at work. I’ve spent 2 hours trying to find detailed info for Federal P223F (55g ballistic tip) and P223E (55g BTHP) to no avail (and yes, i’m aware these rounds are “less than ideal” for duty use).
http://www.federalpremium.com/products/details/rifle.aspx?id=208
http://www.federalpremium.com/products/details/rifle.aspx?id=207
Try those…
ETA: Go to nosler’s webpage and you can get the coefficent for either bullet and plug it into your choice of ballistic calculator with your muzzle velocity to get a more real world working number.
Ballistic tip BC: .267
BTHP BC: .189
Wow, you guys are fast.
Thats a pretty big difference in BC. Glad I am doing this now
Thanks!
Unlike sectional density, there’s no set formula for ballistic coefficient. A lot has to do with how the bullet is tested, altitude, muzzle velocity, etc. Also, some bullet makers are not shy about tweaking published BC figures to increase sales. Older Sierra loading manuals go into great detail on the whole BC issue.
If you’re looking to compare drops or retained velocity, you’re far better off doing it with each individual rifle/sight combination.
What exactly are you trying to accomplish?
Okie John
I use the KAC BulletFlight Military iPhone app. It can calculate a G7 or G1 coeff from observed drop values.
I recommend asking people to let you know if the value is G1 or G7, as just a raw number without definition can be highly misleading, esp if you aren’t familiar with the values.
I know of no mfg that posts BCs using G7 drag formulas.
For the 55 BT variant, just use the posted BC from Nosler’s website. It won’t be that far off. And just find a close proximity to the BTHP from Hornady’s/Sierra’s/Nosler’s websites. Again, they won’t be that far off.
And lastly, don’t treat each published BC as gospel. They are good guides, but there are enough variations in velocities between different guns, and test techniques between mfg’s that it’s not a good idea to compare comapny A’s figures with company B’s figures. Maybe the first two digits, but the third digit, fuggedaboutit.
Here is a good resource for this kind of info.
Nor I, but there is lots of M855/M193 stuff on the net with G7, and pluggin that into a G1 model will make for interesting results, as I have seen.
Just a broadening of perspective, not diminishing your input.
Great point I would not have even thought to mention it, I guess I consider it more advanced knowledge.
BigLarge
What are you doing with the info? Just interested in your departments intent, always glad to see LE agencys thinking ahead.