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What's Wrong With .30 Caliber? By Bryan Litz

 
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  #15  
Old 02-06-2009, 03:27 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

I'd like to try some heavier bullets but won't twist rate be a limiting factor? I currently have a .308 1:12.

Great article!

Jon
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  #16  
Old 02-07-2009, 09:24 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

great artical brian,down here in nz, the 7mm is the most popular for hunting considering most lr rifles are built light for packing in and the ballistic advantage that you coverd in your artical. most of us seem to shoot light projectiles compared to your artical as 162 gr amax is the most popular.
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  #17  
Old 02-08-2009, 05:01 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Brian, great article. I am a mechanical engineer and enjoy the technical discussion and your understanding of and experience with the subject. The scaled comparisons is exactly the type of information I need to assist in selecting a chambering begin my next rifle build.

I am just starting long-range target shooting at Quantico MCB in an effort to increase my long-range hunting ability. To that end, I have been practicing with a 300 WSM that I built as a compromise between elk hunting and target shooting. I shoot 190 SMK because of seating depth with my current throat and the fact that I want the rounds to feed from the blind magazine. I could increase the throat so that I can achieve max powder capacity with current 220, 240 gr VLDs, but I still want to chamber my favorite 180gr hunting bullets. I have made a study and also found that the heavier bullets are lacking in their form factor. I am glad to see that I arrived at a conclusion that is agreement with your more extensive experience and expertise.

After a couple and practices and shoots, I have been bitten by the target shooting bug and am now considering a purpose built rifle for target shooting competition. I was considering the 6.5 x 284 however the 7mm WSM is also interesting.

I make the following observations and comments with the understanding that Brian's article was directed at target shooting and not hunting. However another member made some comments/inquiries about downrange performance on game so I would like to weigh in on the hunting aspect of the .30 cal versus the smaller calibers while keeping in mind that the subject of bullet terminal performance on game is, due to lack of specific testing and data, a somewhat subjective and anecdotal driven subject.

While a smaller caliber bullet can certainly be selected for a high BC and launched at the required velocity to compete with or exceed .30 cals in the kinetic energy department downrange there are other factors to be considered. Terminal performance on game such as elk, moose, or bear is in addition to kinetic energy, heavily dependent on momentum which is a function of mass x velocity where mass has equal contribution to the momentum function value. If a lighter bullet strikes a bone with the same kinetic energy strikes as a heavier bullet but with less momentum, typically the lighter bullet will damage the bone, but deposit most of it's kinetic energy to the bone and surrounding tissue at that point since velocity is dramatically changed while the heavier bullet will likely damage the bone and continue on to the vital organs with more overall energy due to its' larger momentum value.

Thanks again Brian for the excellent article. I look forward to your next article.

P.S. I am glad to hear that girls make excellent shooters as I am trying start my daughter into the sport.
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  #18  
Old 02-09-2009, 09:37 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Jon,
Our heavy .308's are being designed to work in a 1:10" twist.

SlimT,
Thank you for your clear explanation of KE and momentum. As you acknowledged, the stated focus of the article was target shooting where neither are important, but they are very important for this (hunting) crowd.
The differences between KE and momentum are not obvious. My usual momentum consideration is recoil which is proportional to momentum and not KE.
Your explanation of how the two are different on impact is something I've never considered and is quite enlightening.
Score 1 for the heavy calibers!

Thank you,
-Bryan
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  #19  
Old 02-09-2009, 11:54 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Bryan, that was a great article and one I will reference often to shooters on another site. There is a long standing belief that heavier bullets drift less in the wind. No mention of bullet form is ever discussed.

Your article nicely compares all cals and weights that produce similar ballistics. And from real world shooting, that comes very close to my reality too.

What I would like to see in the bullet industry is some standard for generating BC values so that shooters can get a fair comparison of potential ballistics.

Of course, I understand as a marketing tool, that number can make or break a shooters choice thus affecting sales. But varying G forms, ogive shapes, ways of measuring/generating BC's, the number is becoming more opinion then fact.

Could get some increased competition in making more aero bullets?

I like what you are doing at Bergers and noticed the BC values are changing more in line with what we see when a primer is popped. Great stuff.

I have also quickly moved away from the 30cal to the 22 and 6.5. New High BC bullets and a general hate for recoil has made this choice easy. I can expect that as new bullets in larger cals exploit the shapes used in smaller cals, the playing field will once again be leveled.

Larger heavier bullets will offer higher BCs so LR performance will be superior when launched at the same speed. Of course, recoil will also be higher but that is the price you pay.

Look forward to more articles and info from you...plus new offerings from BERGER.

Take care.

Jerry

PS can you explain why there seems to be an upper limit on how heavy/long we can make a bullet? 22cal seems to max at 90gr, 6mm at 115gr, 140ish for the 6.5's, etc

Is it a material strength issue? would going to a lighter core help?

would be wonderful to see a 150gr 6.5 with a BC of 0.65 but no one seems to want to make a VLD bullet heavier/longer.
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  #20  
Old 02-09-2009, 02:16 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Quote:
Originally Posted by Mysticplayer View Post
What I would like to see in the bullet industry is some standard for generating BC values so that shooters can get a fair comparison of potential ballistics.

Mysticplayer,

This is a guess, and hopefully Bryan will correct me on this, but I think BC is a constant, and should be static from gun to gun, and even (when adjusted for) all other variables including pressure. However, in the real world, you'll get different measured values for different guns, different elevations (even when corrected for), plus other factors, for the same bullets. I think this is because, and again I'm guessing, the amount of time a bullet will take to stabilize, will change depending upon equipment and environmental factors. I've heard of a bullet that would stabilize at one elevation and key hole at another - same gun/load/bullet. I think all BC calculations assume that the bullet is stable right out of the barrel. But if it pitches and yaws for a while before is spirals tight, its velocity will decrease faster than it would if it was stable which should make a difference on measured BC.

Also, there is more than one way to skin a cat and I'm guessing that different bullet manufactures don't all use the same method for coming up with their BC's.

I enjoy Bryan's article's too. Hopefully he'll give us some more insight about differences in measured BC's.



Paul
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  #21  
Old 02-09-2009, 02:43 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Thank You Bryan,

Great article, one of the best I have ever read here, and there have been some great articles on this site.
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