Educate me - G-1 or G-7

Discussion in 'Long Range Hunting & Shooting' started by memtb, Jul 17, 2018.

  1. memtb

    memtb Well-Known Member

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    I credit most of you folks with far more wisdom than I, so I need some guidance. If I’m using Barnes TTSX or LRX Bullets on a ballistics calculator....should I use the G-1 or the G-7 program. I attempted to use the Barnes site, and may be more confused than before looking! Any and all help is appreciated.....Thanks in advance! memtb
     
  2. ShtrRdy

    ShtrRdy Well-Known Member

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    It looks like the BC posted on the Barnes website is a G1.

    What caliber and weight are you considering? Maybe it has a G7 in the Bryan Litz book.
     
  3. memtb

    memtb Well-Known Member

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    .375 cal. 270 grain LRX....Barnes lists it as .499 BC I’d like to run it on a program, just to get an idea of potential down range performance! Thanks for whatever you can come up with! memtb
     
  4. MudRunner2005

    MudRunner2005 Well-Known Member

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    For flat base bullets use G1. For boat tail rifle bullets use G7.

    G7 is more accurate for boat tail bullets, which is why we recommend using it over the G1 BC for this type of bullet. Pistol bullets and flat base rifle bullets the G1 BC is used.
     
  5. memtb

    memtb Well-Known Member

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    I guess this is where I’m confused..... how did Barnes assign their BC? Based on the G-1 or the G-7, or does it matter? memtb
     
  6. MudRunner2005

    MudRunner2005 Well-Known Member

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    G1 was the original. Then some guys started calculating G7 BC's, and realized it works better for boat tail bullets, so most of the companies that manufacture LR bullets, will give both a G1 and G7 BC, along with an SD (Sectional Density) number.

    Barnes has never been known to have very high BC bullets... Therefore I'd assume they use G1, like most manufacturers. If you want a guaranteed answer, it probably wouldn't hurt to shoot them an email asking them. Then you'll know for sure.
     
  7. memtb

    memtb Well-Known Member

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    Thanks.....I’ll contact them! memtb
     
  8. Bravo 4

    Bravo 4 Well-Known Member

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    That would be a G1, if it were a G7 of .499 then that would make it have a G1 of over 1.0! No way any Barnes bullet can do that, no way any 270gr .375 bullet made has a G1 that high. Look at it compared to a .375 bullet that does, like the 450gr Cutting Edge MTH.
    I wish the Barnes had a BC that high, if so they would be the most popular .375 bullets made for LR shooters. I bet I could get them easily over 3600 fps in my Snipetac and they are cheap compared to the CEBs, Hammers, and Chinchagas I’ve used.
     
    Last edited: Jul 17, 2018
  9. Bravo 4

    Bravo 4 Well-Known Member

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    If you want to see what the difference is between a bullet using a G7 compared to the stated G1, take the G1 BC & multiply it by .512. This will give you a good number to start with on the G7. In this case a .499 G1 makes a .255 G7. Punch that into a ballistic calculator and see the difference.
    Ex: in this case I put in 3,000 fps velocity and @ 1,000 yards the difference is some very small numbers...as in 3 fps difference. The difference will get bigger as range increases.
    The particular BC for that bullet fired from your rifle/load has a greater potential to be different than what they advertise. Enough so that the differences in the two drag functions of G1 vs G7 aren’t even worth worrying about. If you plan on shooting ELR, maybe you can get better results with the G7.
    I read this years ago and try to use this for truing most LR calculators. Use the advertised (especially if others find it somewhat true) BC to 500 yards and adjust velocity, then start adjusting BC to match extended ranges. Seems to work pretty well at least to 1000.
     
  10. memtb

    memtb Well-Known Member

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    Thanks to all, and especially Bravo 4 for his detailed explanation! I would like to run it out to a thousand (likely never more), just “because”. I already had a load developed for the 250, and had my turrets built for them, and was trying to get a “reasonably” accurate “guesstimate” as to the differences out to around 1 K. Wanted to see if a change to the 270 LRX could be justified!
    Thanks again, memtb