When to use G1 vs G7

Discussion in 'The Basics, Starting Out' started by goebs66, Jun 7, 2015.

  1. goebs66

    goebs66 Well-Known Member

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    Hey fellas, so just when I thought I had all I needed to dial my scope for 1000 yard shots, Leica 1600B, Kestrel 3500 and Shooter ballistics app. I found out about the difference between G1 and G7 ballistic coefficients... Now my head is spinning trying to figure out which one my ammo uses and what that number is... I've been reading that Bryan Litz book Applied Ballistics for Long Range Shooting has tons of testing on ammo and the G1 vs G7 differences and which one to use for specific bullets. Is this book a must buy if I want to be accurate out to long ranges 700+ yards??
     
  2. chalkeye

    chalkeye Member

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    Use G7 if it's available for your projectile.
     
  3. jf239

    jf239 Well-Known Member

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    Brian's books will help inform you and give you the knowledge to increase the probability of hit, our decrees the probability the probability of a miss. Cab you do it with out reading them? Probably, if everything falls into place. Just like everything litz explains the g7 form factor will increase the potential accuracy by being calculated off of a bullet that is closer to the same dimensions as the bullets most shoot for long range accuracy. G1 is based off of a flat base bullet, not the boat tail bullets we all use. Just this will get your theoretical trajectory closer to what it will be in real life. Which in turn will help you put rounds on target. IMHO, I read and study everything I can about ballistics, shooting, accuracy, performance, success, problem solving and much more. By doing this it helps prepare me to make informed decisions when I'm having a problem or in a clutch situation behind the rifle
     
  4. Ridgerunner665

    Ridgerunner665 Well-Known Member

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    I don't think ANY modern spitzer type bullet fits the G1 profile...it looks like an artillery shell...no modern bullets look like that, with the short pointed nose.

    G5 appears to be the best fit for most non VLD type hunting bullets...G7 fits VLD type bullets best...

    Put simply, G1 is quite a ways behind the times...

    With that said, I doubt you'll see G5 BC's printed on bullet boxes anytime soon.

    I don't mean to cloud the issue any more than it already is, but the best bet for putting rounds on target at 700 yards...is to work your way out there from say 300 yards, taking notes along the way.

    In other words...work out your own true BC numbers...use G7 drag functions for VLD type bullets, but I'm not sure G7 fits bullets like the Nosler Accubond or Swift Scirroco any better than G1...those bullet shapes are sorta in between...and that is G5.
     
  5. bigngreen

    bigngreen Well-Known Member

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    I would say Litz book is a solid help and good info written in a way that every one from the layman to ballistic geek will learn from it but it is not necessary to be able to shoot.
    I'll disagree with the previous statement about shooting and finding your own BC, if you use a quality G7 BC like is on the side of a box of Berger bullets and your not within stupid close then you have other issues. You can shoot every 100 yards and force a program to give you the corrections you need BUT when you have a dramatic elevation, temp or range change you'll be of again because your forcing it. When you nail your input data you don't need to force a program!!
    There was a time back when Exbal was the ticket that it would take 5-6 stepped G1 BC's to express the trajectory of a 300 gr SMK to a mile, now I can take the single G7 number from Litz and take it a mile + with expectations of only needing to tune my velocity a little, but nailing all my inputs with a quality G7 lets me narrow down my tuning to just a couple slight variables.
     
  6. goebs66

    goebs66 Well-Known Member

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    Ok this clears thing up SO much! Thanks for the help! So if a box of ammo (current LR rifle is a 7mm rem mag) shows a BC I should assume its G7??
     
  7. bigngreen

    bigngreen Well-Known Member

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    No assumptions, a box of Bergers will have the G7 and G1 clearly marked because they also have the G1 there so you can compare to a bullet that is marketed with only a G1. For ballistics you want to use a G7 so you have three options, use the G7 on a box of Bergers, use a Litz BC that is proven for another bullet or figure out your own G7. Figuring out your own is the last option right now till you learn how to get solid inputs for every other bit of data and since your guessing on the BC you need to have a velocity with in a few FPS that you can trust to tune your BC to, much easier to start learning with a proven BC :D
     
  8. jf239

    jf239 Well-Known Member

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    Most are g1, pretty much if the number is anything over .35 or so with must ammo it is g1. Berger advertises g1 and g7 but most are g1. Both the shooter app and applied ballistics app can provide a g7 BC for most bullets even if the ammo provider doesn't. Litz has done all the hard work for us
     
  9. FearNoWind

    FearNoWind Well-Known Member

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    IMO, if you don't have it in your reloading library you need to get it. It's the single best book of its kind I've ever read.
     
  10. jf239

    jf239 Well-Known Member

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    Agree^