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G7 > G1 ; resistance to BC change

 
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Old 05-04-2011, 09:17 AM
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G7 > G1 ; resistance to BC change

Rather than inventing my own wheel , I read then evaluate and IF warranted CHANGE. Yes, there is resistance to change but Bryan Litz's Second Edition Applied Ballistics For Long-Range Shooting (which includes the G7 or G1 software program CD inside the backcover) is so informative and shooter readable, I am changing. Specifically, for LRH I'm shooting VLDs and changing to software using G7 BCs for ranges where the retained velocity is less than 2,000 fps. AND this second edition contains 225 independently measured BCs (hint not company advertised). That's what I think I know, anyone out there know something better ? What is LAG TIME, DANGER SPACE and who is John Galt ?

Somewhere Between Ignorance & Arrogance,
CRaTXn
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Old 05-04-2011, 01:09 PM
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Re: G7 > G1 ; resistance to BC change

I've called Bryan's book "revolutionary" before. Because it's high time the shooting sports industry get with the program and accept that for almost all long range bullets, the G7 is the way to go, and that the average shooter is not too dumb to know the difference between G1 and G7.

That said, there are some bullets for which G1 is better. If it's flat based and blunt, G1 is likely to be a better fit than G7.

To bring home the point, I wrote a ballistics calculator using Bryan's data (sadly, only from the first edition - I don't have a copy of the 2nd yet). (You can find it at Bison Ballistics Calculator - it's free for all to use). I've set it up to automatically choose the best drag function. (Almost all are G7, but I think that says more about the bullets Bryan selected than the overall superiority of G7 in general).

So no, you're right on. It's time for a long overdue change. Best tool for the job and all that.
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Old 05-04-2011, 02:06 PM
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Re: G7 > G1 ; resistance to BC change

Thanks for the feedback from someone whose knowledge base sounds extensive. Speaking of "bases" yes "flat bases" but your remark of "and blunt" I am going to take that to mean "spitzer" ogive nose as that is what the German Krupp bullet of 1888 that I understand the G1 was based on had ...as opposed to what we Americans would take "blunt" as a dumdum / flat or ball / round ogive nose...is that correct from what you know. Thanx for the Bison Ballistics program offer I will take advantage of it. Using the G1 for my VLD is indeed BS in BS out.I don't have the 1st Edition of Bryan's book but if this is like most things; it's better the second time around.
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Old 05-04-2011, 02:17 PM
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Re: G7 > G1 ; resistance to BC change

A real life example are some of the Barnes bullets. All of those in my calculator use the G1 (as is appropriate). It's not an exact sort of thing - long and pointy with a boat tail generally means G7. Flat base with a shorter, less pointy nose generally means G1, but you really need to test them to know for sure which will be better.
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Old 05-04-2011, 02:41 PM
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Re: G7 > G1 ; resistance to BC change

CRaTxn,

The standard bullet used in most of these early tables is essentially quite similar; a 2 caliber radius, flat based, and 3 calibers in length. Not terribly sharp, but certainly not a flat nose or round nose, by any means. This is the basic profile for the standard in the Krupp, Gavre, Mayevski, Ingalls an G1 tables. It's fairly blunt in comparison to the average hunting or modern match bullet, most of which have an ogive of around 7-8 calibers. The VLD styles generally run anywhere from 12-15 calibers, if that helps.
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Old 05-04-2011, 03:04 PM
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Re: G7 > G1 ; resistance to BC change

Thanx Kevin that is a succinct answer...am I correct in differentiating nose ogive as separate from meplat?
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Old 05-04-2011, 04:38 PM
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Re: G7 > G1 ; resistance to BC change

The meplat is the small flat at the end of virtually any bullet, normally .050" to .060" on a match type hollow point, depending on how small of a knock out punch the maker is using. They close them up as much as possible, but it's virtually unavoidable that there will be something of a flat at the tip. From that point back, it's ogive, until it blends into bearing surface. Very noticeable on Secant ogives, not so much on Tangent ogives. You might take a look at Hatcher's Notebook for some more info on these earlier tests. Everyone today seems to assume that the G7 profile and long ogive bullet is a newer development. Not so. Some of the older drag models, such as the Hodsock, British 1929 or Aberdeen "J" projectiles were quite streamlined. I just got Bryan's newest version last week and haven't had a chance to get through it all yet, but I bet he mentions these somewhere in the historical descriptions.

Either way, Hatcher's is a must read for any firearms buff.
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