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

 
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Old 02-06-2009, 08:48 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Nicely done. I shoot a 7WSM for F-Class running the Berger 180s at 2,900+ fps and in some circumstances, it seems like an almost unfair advantage in teh wind. I love it!

The question I have is more related to this kind of site and others of similar perspective. When you essentailly remove recoil from the equation (as in I'm using a muzzle break) and add in a need for energy delivered at the receiving end of a long range shot (meaning killing and knock down power at ranges out beyond 800 or even 1,000 yards), we seem to gravitae away from the 6.5 and 7mm bullets back to the heavier bullets, even if they are slighly lower in BC and form factor. Is it possible for you to update your article and include the .338 bullets in the analysis?

JeffVN
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Old 02-06-2009, 09:08 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Thanks for reading my article and for the comments guys.

britz,
Thank you for your critical analysis. It's good to challenge ideas that don't mesh with observations. Let's put your comparison of the .30 cal 190 and the 7mm 168 under the microscope.
I agree that the .30 cal has 18% more (base) surface area and only 13% more weight than the 7mm, which means the 190 can be expected to have a little higher muzzle velocity. As you point out for two magnum cartridges, the difference is about +50 fps in favor of the .30 cal for these bullets.
The 'disconnect' between the above math and my position in the article is that the 7mm 168 and the .30 cal 190 are not equally proportional for their weights. In other words, the 7mm 168 is quite heavy for 7mm, whereas the 190 is a middleweight for .30 cal. If you scale all the dimensions of a 7mm 168 grain bullet to .30 cal, the bullet would weigh 214 grains. The 190 grain .30 cal bullet scales to a 149 grain 7mm bullet.
In order to do this scaling exercise, multiply the bullet weight by the cube of the caliber ratio. In equation form: 168 * (.308/.284)^3 = 214. You have to cube the caliber ratio because weight is proportional to volume, which is proportional to the cube (lengthXwidthXheight).
This is similar to the principle you used to scale the base area of the bullets. Area is proportional to the square of the caliber ratio. (.308/.284)^2 = 1.18, or 18% difference.
So in your example with the 30 cal 190 and the 7mm 168, the reason why the 30 cal can achieve higher velocity is because the 190 is proportionally lighter for the caliber than the 168 is for the 7mm.
Another thing to put under the microscope is the advertised BC's for these two bullets. I've measured BC's for many bullets using the same method that's repeatable within +/- 1%. The measured BC of the .30 cal 190 MK is 0.527 (average from 3000 fps to 1500 fps). This is practically identical to what Sierra advertises for this bullet. The curve ball is the 7mm 168 MK. Using the same measurement technique, I measured a BC of 0.565 (average from 3000 fps to 1500 fps), which is about 13% higher than advertised! It's not hard to believe if you consider the sectional densities of the bullets (0.298 for the 7mm vs 0.286 for the .30 cal). BC is mostly dictated by sectional density, with a correction based on form factor. If both bullets had the same form factor, you could expect the 7mm to have a 0.298/0.286 = 1.04 times higher BC than the .30 cal. In fact, the 7mm has a measured BC that's 0.565/0.527 = 1.07 times higher than the .30 cal, which means the form factor is about 3% better for the 7mm. Looking at these bullets side by side, it's believable.
When I visited the Sierra plant in Missouri this past fall, I pointed out that they were underselling the BC's on their 7mm bullets. They said "we know". I asked why they don't correct the advertised number. A shrug is all I got.
I hope this helps to answer your concerns about the apparent contradiction between my article and your observations with the 30 cal 190 and 7mm 168 bullets.

threethreeeight,
You make a very good point about kinetic energy favoring larger calibers. I wrote that article for the context of target competition where (as you pointed out) KE is a non issue.
There is something to say for the smaller calibers though...
Consider a 150 grain and a 200 grain bullet impacting a target at the same speed. The 200 grain bullet will hit with 200/150 = 1.33 times more KE. Now consider the effects of velocity. If the 200 grain bullet hits at 1800 fps, it will deliver 1437 ft-lb of KE. The 150 grain bullet would need to hit at 2078 fps to deliver the same energy, which is only 2078/1800 = 1.15 times the velocity of the 200 grain bullet. The point is that KE is more dependent on velocity than weight. If a lighter, but higher BC bullet can strike with more velocity, it helps to make up for the fact that it's not as heavy as a larger caliber bullet.
Just some more food for thought.

Buffalo Bob,
There are 230 grain .30 cal's on the drawing board (Hunting VLD and BT Target) right now. They'll need to be made on the same press as the .338's, so it's gonna be a while but the need has been identified and they're coming.
I'd be happy to talk about Palma shooting with you, but I can't guarantee you'll beat your daughter! Statistically, girls are hands down better shooters than guys!

Take care guys, and thanks again for your comments,
-Bryan
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Old 02-06-2009, 09:13 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Bryan, I am so pleased to have you on our site!
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Old 02-06-2009, 09:32 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Bryan, Thank you for the wonderful argument. Now I kinda wish I'd have gone with a 7mmwsm lol! As Len said, It is great to have you aboard! Aw shucks, I still gotta soft spot in my heart for a nice 30 ca.
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Old 02-06-2009, 11:24 AM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Thanks for the excellent article, Mr. Litz! I too am pleased to see you here.

I've been shooting the 6.5s (.260, 6.5-284 & 6.5-300WWH) for quite some time, and am considering a good 7mm for my next build, based on the much same opinions you put forth in your article.

A good friend and shooting partner shoots a .300WinMag with Berger 210s at about 2,950, while I most often run my 6.5-284. We shoot to 1,200 yards regularly and our trajectories are nearly identical, but he seems to enjoy a little less wind drift. The single biggest reason I would have for going to the .300WinMag or similar cartridge would be IF I needed the extra terminal energy and I can say for sure that his bullets are much easier to spot at 1k+ than my little 142s. Otherwise, I'm sticking to the easier to manage stuff in the 6.5 to 7mm range.

BuffaloBob, I feel your pain . . . my own beloved daughter beat me at the last Quantico F-class match in January, using my own .260 no less! I will definitely work harder at it this weekend. We have back-to-back matches, a local tac match on Saturday, then the QMCB F-class on Sunday, so I'll have two chances. If she continues to win, I may decide that it's time to move her up into a .300 RUM or .30-378 with 240s, LOL.
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Old 02-06-2009, 02:05 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Quote:
Originally Posted by Buffalobob View Post

I did not know you were the national Palma Champion, may be you can give me some help so my daughter doesn't beat me so often.
Buffalobob,... I found this on youtube - hell,...with open sights and no rest,... I can shoot this good with my eyes closed, as long as I'm actually asleep and dreaming.

YouTube - Palma shooting at 800 yards


Quote:
Originally Posted by bsl135 View Post
I'd be happy to talk about Palma shooting with you, but I can't guarantee you'll beat your daughter! Statistically, girls are hands down better shooters than guys!

-Bryan



I wouldn' t say that my daughter is a better shot than me, but for some strange reason, my guns shoot tighter groups when she's is behind them. I always blame it on the wind. The big question is, why does the wind die down when it's her turn every damn time?









Paul
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  #14  
Old 02-06-2009, 03:16 PM
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Re: What's Wrong With .30 Caliber? By Bryan Litz

Holy Smokes, there weren't even any new holes being made there at the end. I would just say his spotter or scorer is just about as incompetent as me. Can't count past ten without taking his shoes off and doesn't even remember how many there are supposed to be.
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