How To Work Out Come Ups Without Knowing BC?

[STAMarine]

I have a metric s*** ton of 1963, 1964, and 1972 M118 LC 173 gr Match that I got from my father. I know this ammo isn't as accurate as the Fed GMM 175 I usually shoot, but it's free, I see no reason to waste it, and I can only get out to 859 yds on my farm due to terrain anyway. I can get velocity with my Labradar, but I don't know the BC of this round. I usually just input my info in Hornady's Ballistic Calculator and then confirm at range, but is there a way I can find out the BC for this ammo so I won't have to start out cold at each chosen yard line?

[georgeib]

I would start at the .494 G1 and see how close that gets you. That's the claimed BC. Should be close. Another sheet claims it as .530, but that seems really optimistic.

[sinister]

I'd just run a ballistic drop table using JBM Ballistic, free on-line. The 175 Sierra Match King in the bullet library should get you close. As posted above, a G1 BC of .494 should be close (what the Army used with 173s loaded in M1 30-06).

Plug in your variables (barrel length, velocity, twist, sight height over bore, temperature, etc.) and it'll calculate a table you can start from.

https://www.jbmballistics.com/cgi-bi..._drift-5.1.cgi

[STAMarine]

Thank you both! I'll try it out this weekend and will see how things go.

[sinister]

Good luck!

M118 "White Box" Match was leagues ahead of the later "Special Ball."

More like Special Olympics Ball. Couldn't call it "Match" because it wouldn't pass GI acceptance standards.

Save your brass -- you can reload it later with 168s and 175s later if you can find IMR 4895, 4064, Reloader-15, or Varget.

[STAMarine]

Good luck!

M118 "White Box" Match was leagues ahead of the later "Special Ball."

More like Special Olympics Ball. Couldn't call it "Match" because it wouldn't pass GI acceptance standards.

Save your brass -- you can reload it later with 168s and 175s later if you can find IMR 4895, 4064, Reloader-15, or Varget.

Will do. I have reloaded my precision ammo in the past, but we had a son in September so I haven't had time to reload. Shooting the 173 will save me alot of cash over buying my standby GMM.

Of course, when I say I've reloaded my "precision" ammo, I'm still not doing any better than GMM anyway, it's just cheaper.