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  1. #1
    newshooter
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    Default Ammo Questions-308 vs. 338 Fed

    I am a new member and glad I found this site. My questions to the gun guru are:

    If the 338 federal is merely a necked up 308 win, then how come a 180 grain 338 can travel faster than a 180 grain 308? For example, a 180 grain 308 travels at 2620ft per second vs. 2830ft per second for the 338 fed. If it is the loading, then can one loads up a 308 to a higher pressure without an issue? Thanks in advance.

  2. #2
    h2oking
    Guest

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    You have asked a very intelligent question and I don't have a clue. Just kidding. Pressure is usually described/measured as PSI (pounds per square inch)think about it for a moment. If you were to push lets say 100 pounds of pressure on an area key word here of one inch square and then push another 100 pounds of pressure on the square inch next to it you are applying 100 pound per square inch of area but you are actually pushing 200 pounds. So, because a 180 grain .338 bullet has more area to push on than a 180 grain .308 bullet it will be pushed faster because of the larger area. To be exact on how much more area can be calculated by PI(3.142) X the radius squared to find the area of both bullets.
    Now lets go back to my 100/200 pound example; if you were pushing 100 pounds on just one square inch, what ever you were pushing would only see 100 pounds pushing it. However, as you go up in area more pounds are pushing even it at equal PSI. A larger diameter bullet of the same weight as a smaller diameter bullet will always go faster than the smaller bullet assuming both are being push by the same PSI. I hope that helps, if I need to explain it further I would be glad too.

    Ron
    Last edited by h2oking; 09-12-2008 at 01:22 AM.

  3. #3
    newshooter
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    Default

    Thank you very much. Your answer make sense to a certain extend. If I understand the logic correctly, then a 100 grain 308 (if they make one) will travel faster than a 100 grain 243, right? Sorry for another not so smart question.

  4. #4
    tke805
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    the h20king gave you a great answer and i'll let him answer your second ques. i only want to add that types of powder, barrel length and powder burn rate all factor into the equation as well as the angle of the shoulder on the brass and the o.a.l of the chamber/bullet.lots of factors to add huh?

  5. #5
    h2oking
    Guest

    Default

    It was a very smart question, it is not a simple answer unless you are familar with physics which I am. I would bet you could teach me a thing or two on a myriad of other subjects and to me that is what this forum is all about. Yes, assuming they were being pushed with the exact same pounds per square inch. Most high powered rifles are loaded to around 55,000 PSI so in my example both are assumed to loaded at the same PSI.

    tke805, you ended your sentence with a question mark so I assume you were asking me if what you mentioned was a factor and the short answer is no. The reason being I was only comparing the laws of physics as they apply to pressure measured in PSI and not comparing burning rates of powder, rifling twist or barrel length. If you have a question about that I have been reloading for over 50 years so at least I think I have learned something and I love to share so fire away.

    Ron
    Last edited by h2oking; 09-12-2008 at 04:21 PM.

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