Discussion in 'Technical Articles - Discussion' started by ADMIN, Feb 4, 2009.

What's Wrong With .30 Caliber?

  1. ADMIN

    ADMIN Administrator

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  2. tillroot1

    tillroot1 Well-Known Member

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    Bryan, great article, I agree with what you have to say, Thanks for taking the time to provide something for us to read! Ron Tilley
     
  3. britz

    britz Well-Known Member

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    Wow, that was a technical based article. Now I will admit to being a little intimidated by the knowledge base that the author obviously had, but I'm going to challenge some of what he said.

    If I understood correctly he said that a moderate 7mm will push a heavy weight bullet as fast as a Very large mag 30 cal will push a heavyweight bullet. And he said that the BC of the heavy 7mm and the heavy 30 are "vertually" the same.

    He also conceded that the 190 class 30 is comparable to the 168 class 284. I looked at the WSM's and the 7 pushing a 168 is going around 50 or so fps slower than the 300 will push a 190 according to Hodgdon's data (rough numbers of course but the point is that the 30 will push it slightly faster). I beleive this makes sense because of the PSI and the surface area that the respective bullets have. larger surface area and same weight = higher veleocity. Simply put, taking a 30 cal and a 284 cal in terms of Pounds per square inch the 7mm will require to be multiplied by 1.18 to equal the square inches of the .308.

    It is true that the 190 is heavier than the 168 also, but you only have to multiply the 168 by 1.13 to equal the 190. SO... if my rough math is right then the 30 cal will always have a slight advantage over the 7mm due to the fact that the increase in surface area being pushed increased faster than the weight of the bullet (in this class).

    ALSO, if you consider that the 190 has a higer BC than the 168 (@.53 to 49 respectively).

    HOWEVER, and a big "however" that is... Recoil is a major issue and I will definately concede that the smaller 6.5 and even the 7mm's give up small amounts of BC to reduce large amounts of recoil.

    VERY Cool article and a good brain teezer (hopefully I was somewhat close in my figures otherwise I'll have to stick my tail between my legs and run home lol!)
     
  4. britz

    britz Well-Known Member

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    upon further reflection, There must be something I'm missing or over simplifying because you can not dispute the fact that a 260 rem shooting a 140 grain bullet will hold the same tradjectory as a 300 win mag and a 190 smk. Same BC and same velocity. Much smaller bullet and smaller case.... Man! I hate being wrong! LOL
     
  5. Dano1

    Dano1 Well-Known Member

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    Yeah, and the 6.5x.284 pushes it even faster meaning a higher BC. Kind of makes sense as to why they are so popular.

    Very good article, I have to read it a few more times to understand it all especially the big "techical" words. :D

    I'm learning more every day....


    Dan
     
  6. threethreeeight

    threethreeeight Member

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    Thanks for the article it was an excellent read and very informative thank you,
    I wonder if it is not just down to the ballistics,is it because behind us down the track aways people would use a hunting calibre for long range target shooting,the smaller calibres you talk about indeed have the energy to hit a target,whether it be a balloon or paper or steel gong,however they can't match the Killing energy at those long long ranges of the 7mm and 30 calibres in a genuine hunting environment,They don't need the energy and so have developed smalller lighter recoiling calibres for their purpose.
    Regards.
     
  7. Buffalobob

    Buffalobob Writers Guild

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    I enjoyed your discussion of the 30 caliber bullets, especially the big freight train 240SMK. I ran a large number of calculations on the bullet fired from a 30-378 versus the 7 AM with the 200 grain Wildcat. The only thing you could say about the 240 SMK was it had 20% more weight when it landed but it was a dog in the air. My decision to go with the 7AM was what you said about recoil, I am just not one of the people who like to lie awake at night with a bruised shoulder and even a 308 will do that to you after 50-60 rounds.


    The only important question I have is now that we know that you know what we know, what are you going to do about it? Can we expect Berger to bring out a high BC 250-250 gr bullet? And will it with stand a muzzle velocity that will make it useful at long range?


    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. :D
     
  8. JeffVN

    JeffVN Well-Known Member

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    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
     
  9. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    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
     
  10. Len Backus

    Len Backus Administrator Staff Member

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    Bryan, I am so pleased to have you on our site!
     
  11. britz

    britz Well-Known Member

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    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.
     
  12. eshell

    eshell Well-Known Member

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    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.
     
  13. WildcatB

    WildcatB Well-Known Member

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    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





    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? :D



    [​IMG]





    Paul
     
  14. Buffalobob

    Buffalobob Writers Guild

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    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. :D