Improved Cartridge Question

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by J300UM, Apr 30, 2008.

  1. J300UM

    J300UM Well-Known Member

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    I have a question about my new rifle (300 rum improved). I'm assuming my gain in case capacity is going to be toward the top of the case near the shoulder. With that being said, am I waisting my time with the new cartridge by using longer bullets that protrude into the case quite a ways? Or will I still be able to take advantage of the extra horsepower to push heavier bullets? I want to load my rounds to fit in the mag if that has any influence on your answers. Thanks!!!
     
  2. jwp475

    jwp475 Well-Known Member

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    I don't think that an Improved 300 Rum will gain enough aditional powder space to make much of a difference. A 10 percent increase in powder capacity will give a 2 1/2 percent increase in velocity at the same pressure. The RUM case doesn't have much taper to begin with. You could install a longer magazine and seat the bullets out farther and gain a bit of capacity that way. That is what I did with a 338 laupa I had a detachable box mag installed that allows me to load to 3.885" COAL insted of 3.6"...
     
    Last edited: May 3, 2008

  3. Mikecr

    Mikecr Well-Known Member

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    No magic, capacity is capacity.
    And nothing is free...
     
  4. .280Rem

    .280Rem Well-Known Member

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    Why would anyone "improve" a 300RUM for cryin' out loud?
     
  5. Varminator 911

    Varminator 911 Well-Known Member

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    Improved 300 RUM

    The 300 RUM is at it's best with the longest, highest BC bullets. Therefore you need a longer magazine and probably a longer throat to use all that case capacity. You also need a long barrel.

    The only way to truly improve a 300 RUM is to open up the neck, ie 338 Edge.
     
  6. J300UM

    J300UM Well-Known Member

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    Improving the 300 rum was something my gunsmith talked me into. I was fairly ignorant at the time and it sounded pretty cool to me. If I knew then what I know now, I would have definately had the gun chambered to 338 edge. Im waiting on a smokin deal for another 300 or 338 rum to use to build an edge. Btw, thanks for the critisism... I mean advise.
     
  7. James Jones

    James Jones Well-Known Member

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    The 300RUM is already overbore so any addition increase in capacity will yield very little increase in speed , once you get past the 300 win mag size cases you pretty much reach a point of deminishing return , yes you will gain some speed but for the ammout of powder increased its minimal.

    That being said their are more benifits of the Ackly improved case desgine than just added case capacity for speed , the sharper shoulder angle and decreased body taper reduce bolt thrust a good bit and also slow case streaching to nearly none. Your chamber isin't a problem with the bullets seating depth , you will still be able to seat the bullets to the same depth even with the increased capacity , I would however have your gun fitted with a Wyatt's mag box and that will allow you to seat your bullets out a good bit further and this will let youuse VLD's and still feed from the mag
     
  8. .280Rem

    .280Rem Well-Known Member

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    It wasn't a criticism, it was a valid question, as I think you now know. I'd go have a talk with that smith of yours! I'd talk refund, or maybe some free work! Sounds like he just made up a reason to take your money!
     
  9. P KUNDA

    P KUNDA Well-Known Member

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    The case is big to start with

    A longer magazine would be a sensible the way to go, if one is going to all that trouble to enlarge the case capacity.

    Peter
     
  10. Lightvarmint

    Lightvarmint Guest

    You can probably find you some dual diameter bullets that will allow the bullet to be seated farther out prior to touching the lands. That way you can take full advantage of the new powder capacity of the case.

    James
     
  11. britz

    britz Well-Known Member

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    Easy fella ;)

    Like Jones said, there are other advantages to the improved version. He isn't the first one to do it and won't be the last. Case capacity is case capacity. I agree with the others that getting a longer mag put in to allow you more room for longer bullets is the way to go.

    Good luck with your rifle and happy shooting.
     
  12. J E Custom

    J E Custom Well-Known Member

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    J300

    I wouldnt be two hard on your smith because he probably thought
    he was helping you out.(Not defending him )but he should have
    explained how much bang you were getting for your buck.

    You did'nt hurt your self and second thoughts are your worst enemy
    when building a custom rifle. Most all smiths have an opinion as to what
    is best for its intended use and I am no different "BUT" I do tell the client
    the advantages and disadvantages of each choice and then let him/her
    make the decision.

    As to the term "IMPROVED" I have owned several P O Ackleys that were
    built by himself and they were originally based on cases with fast tapered
    bodies and 25 to 35o sholders. These rounds were truly Improved by
    blowing the body out to a minium taper that minimizes bolt load and
    improves brass life. Also by changing the sholder taper to 40o or more
    it added volume but most important was that it improves/changes the
    burn rate and pressure wave inside the case making it more accurate
    most of the time.

    On the more modern case designs they are now doing this for the same
    reason. Efficiency, capacity,bolt loadwith higher pressures, and accuracy.

    So as some of the others have said you may not gain much velocity but
    it should be better if only by a small margin.

    So the term Improved should in some cases be called Inlarged,Changed,
    Wildcat'ed, Modified But not "Improved".

    So my recommendation is to shoot and enjoy your new toy and I can
    tell you that you will be empressed if the smith did his part.

    J E CUSTOM
     
    Last edited: May 10, 2008
  13. jwp475

    jwp475 Well-Known Member

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    J E Custom is spot on in his post... I thought that the original post that started this thread was asking advice before the build, and that is how I based my intial response.
     
  14. J300UM

    J300UM Well-Known Member

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    Thanks for the replies! Sorry that I was kind of a smart a$$. It seems like every time I post a question here, people seem more intent on bashin what I have or the questions I have then actually answering them. There is a ton of knowledge here and I would like to aquire some of that. I certainly dont expect answers but I do appreciate the ones I get. Maybe I took some of the replies the wrong way. Again, thanks!