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Thread: FT/LBS data for shortened rifles required please

  1. #1

    Question FT/LBS data for shortened rifles required please

    Hello all i don't have a chrono yet so I was wondering if anyone out there might be able to help?
    my 243 has a 17 1/2" barrel and shoots 65gr vmax with 40gr varget and 90gr speer hot-cor with 34gr Rel15
    my .223 has a 14 1/2 barrel and shoots 55gr vmax with 25gr of varget
    my 308 has a 18 1/2 barrel and shoots 125gr nosler bt with 47 gr varget and hornady 130 sp with 44gr of h4895
    all these loads shoot excellent but as i don't have a chrono or ballistics data chart(yet!! i'm on the vino at the minute so they might be purchased after a couple more glasses) could anyone advise what fps and lbs/ft these loads would be doing??

  2. #2
    Not really. Conjecture would be the best anyone could offer. If you can guess at the speed, this formula has always worked for me:

    WT x Velocity (Squared) x .000002215 = Ft/lb ME.

  3. #3
    cheers Muir done a few guesstimates will use your formula tomorrow had one too many vinos to do it at the mo
    thanks again

  4. #4
    I multiply fps squared by grains and divide by 450240

  5. #5
    thanks for the formulas chaps
    are the ballistic calculators any good for giving me the info on my shortened barrels or should i just get a chrono and use your formulas?
    cheers again

  6. #6
    And another way also
    Too Old Soon Too Late Smart

  7. #7
    buy or borrow a chrono

  8. #8
    Of course you'll notice both formulae require the velocity..... your going to have to shoot some rounds over a chrono. to get speeds for your load/rifle combinations.

    +1 with Lister Chrono. a must.

  9. #9
    No substitute for chrono to get truly accurate data but Quick Load program is pretty good for getting a fairly good idea of how a load is likely to perform and takes in to account barrel length. Suggest you invest in both when funds permit. I have an 18" barrel .308 and quick load data very close to reality over chrono.

  10. #10
    A chrono will be a far more useful tool than QuickLoad.
    Just to put into context if one does not know how to calculate muzzle energy what use will QuickLoad be if basics are not understood?
    This is not meant as a slight, just pointing out that £150 could be better spent elsewhere.

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