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Rifles, Bullets, Barrels & Ballistics Applied Ballistics


Is this a typo?

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Unread 03-06-2007, 11:09 AM
Gold Member
Join Date: Dec 2006
Location: FREE RUN, MS
Posts: 774
Re: velocity equilizations

We can control X, if we choose X as zero.

That is what our real world goal is. Finding X.
With a varible Y (distance).

So if we define X and Y.......B(3300) and A(3000) we simply gave B a 100yd head start.

Its amazing how huge a 300fps advantage is! [img]/ubbthreads/images/graemlins/grin.gif[/img]
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Unread 03-07-2007, 08:01 PM
Junior Member
Join Date: May 2006
Location: just east of the continental divide, MT
Posts: 18
Re: velocity equilizations

Thanks for the replies. Nyles check out sierras website for conformation of those numbers, and you'll see what I mean. Dzaw, I understand the law of diminishing returns, and what you say makes perfect sense. Just trying to wade through those numbers. Fifty I agree with you, as it only makes sense. However- when you run exbal to extreme velocities with different bullets to extreme ranges all the numbers catch up to each other. I cant remember the exact rounds I used, I think .338 am-7mm am- and 416 barret caught up to each other at 3000 yds. I'll try to do it again(it was a while ago). That may have been what triggerfifty was trying to say.

I would like to relearn bc as cd. According to JBMs website this is more reliable. Shoot I just read mccoys book 6 months ago, their is alot to this stuff and I know very little. One thing for sure the math is intense and god gave me an old public school apple computer for a brain to figure it out.
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Unread 03-07-2007, 08:38 PM
Silver Member
Join Date: Aug 2003
Location: McKinney TX
Posts: 408
No it\'s not a typo

I'm going to jump into this one with both feet...damn why can't I leave well enough alone!

IMHO, what the Sierra ballistic engineers put into their ballistic calculator is the wrong way to calculate ballistics. First they started with a G1 ballistic model by a Russian Col Ingalls Mayevski that is well over a hundred years old and is based on a 1”, one pound round nose projectile. What a great foundation for to calculate today’s modern flat base spire point, boat tail and VLD type bullets. The other reason they chose the G1 ballistic model is because it yields higher BC’s for bullets. The theory is, the higher the BC the more bullets we’ll sell.

Anyhow to get around the short comings of this century old calculation, they had to learn to massage that ballistic model to get better long distance accuracy out of their program. They did this by using multiple BC’s that can go up and down as the velocity decreases.

The US Army at the Aberdeen proving grounds have mathematically worked out more efficient ballistic models which don’t use G1 BC’s for bullets. CD’s are much more accurate, but having said that for small arms the G5 (standard boat tail), G6 (flat base Spire point), and G7 (VLD) ballistic models are hands down more accurate than what Sierra is trying to push. Some of today’s better ballistic programs such as the RSI Shooting lab support those other models.

Think about this, they are using the same ballistic model for any type of bullet. So all types of bullets no matter their design will have the same flight/ballistic characteristics…NOT!

A Sierra .308 175 grain BTHP has a published G1 BC of .505. The actual G5 BC for this bullet .316. Lower BC’s don’t sell well, but the mathematical calculations used for the G5 ballistic model are extremely accurate, a lot more so than that massaged G1 stuff they’re putting out.

Off my soap box, now let the flood gates open…damn why couldn’t I just have left well enough a lone???

Mathew 5:16

Distance is not an issue, but the wind will make it interesting!
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Unread 03-07-2007, 08:40 PM
Platinum Member
Join Date: Jan 2004
Location: Blackfoot, Idaho
Posts: 8,829
Re: velocity equilizations

Anyone have an in with the Mythbusters guys??
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!
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Unread 03-07-2007, 09:18 PM
Join Date: Dec 2004
Location: El Reno, OK
Posts: 1,922
Re: velocity equilizations

was reading a website last night about a guy testing the theory that a subsonic 22 LR bullet would not be disrupted by the transition and would carry more velocity to a 100 yard silloutte traget than the supersonic rounds which had to go through the transition.

[/ QUOTE ]

How about a link!!!
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Unread 03-07-2007, 11:34 PM
Bronze Member
Join Date: Sep 2002
Location: Pocatello, Idaho
Posts: 52
Re: velocity equilizations

I thought everyone new that about 22 projectiles. [img]/ubbthreads/images/graemlins/grin.gif[/img]

Law of diminishing returns (?) also applies here too.

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Unread 03-08-2007, 07:37 AM
Silver Member
Join Date: Aug 2003
Location: McKinney TX
Posts: 408
Re: No it\'s not a typo

To clarify my original post about using the proper drag model to calculate your bullets external ballistic, I thought I use a graph which shows all the drag models.

My ballistic program will let me calculate the exact BC of the bullet I’m shooting in my gun. It will also let me take my results and input the results to see what ballistic model best matches my bullet. With a little reverse engineering, I’ve been able to get my program to match my actual results to 1000 yards with .5 moa. The best I could get it to match using the G1 drag model was around 2.5 moa at 1000 yards.

These results were for my .308 I took moose hunting in Alaska, not that I was going to be shooting 1000 yards. They were for the Barnes .168 gr triple shock bullet BTHP.

The first graph shows all of the different drag models with my Barnes .168 gr triple shock in the upper porting of the graph. The G1 drag model I have an arrow pointed at is the modified and massaged G1 drag model used by many ballistic programs.

I then moved the Barnes .168 gr triple shock down to see which drag model best matched that bullet. As you can see it was an almost exact fit to the G7 drag model for VLD bullets. But you can also see, if I was using the G1 drag model that Sierra and most of the ballistic programs are using my results would not be very accurate.


Mathew 5:16

Distance is not an issue, but the wind will make it interesting!
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