Hello everyone, I have a 50 (.510) Caliber Umarex Hammer that I am shooting Mr Hollowpoint 385 gr out of. I recently ordered a ATN X-Sight 4K Pro and ATN ABL 1000 for it. The rounds I’m using do not have BC information. I went to the GunData website to try to get close to what the BC should be for my round but I am not confident that the 0.346 BC it gave me is correct. The ballistic coefficient calculator did not ask for fps. I guess that is not needed. If someone can guide me on this, I would really appreciate it. Thanks!
Finding Unknown BC for Air Gun Rounds
- Thread starter Cameo557
- Start date
Find a friend with a LabRadar or shoot through a regular chrono at two seperate distances and calculate it with those velocities. Even with knowing your BC to the decimal point, your ATN will still need numbers tweaked to work properly with the ballistic calculator fyi.
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1) Start with the published figure. Get everything set up with your rifle CORRECTLY using that figure.
2) Now zero and shoot a group at 50 yards (5 shots will do).
3) Set everything up for second range say 100 yards. Shoot a group.
4) IF the group is low decrease the BC until the second group prints on the bull.
5) IF the group is high increase the BC until the group prints on the bull.
Done deal ...
Check at a third range if you want more precision.
Edit note that does presume you have a pretty good idea what your muzzle velocity is.
2) Now zero and shoot a group at 50 yards (5 shots will do).
3) Set everything up for second range say 100 yards. Shoot a group.
4) IF the group is low decrease the BC until the second group prints on the bull.
5) IF the group is high increase the BC until the group prints on the bull.
Done deal ...
Check at a third range if you want more precision.
Edit note that does presume you have a pretty good idea what your muzzle velocity is.
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