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Thread: O.A.L. vs C.O.A.L.

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    Default O.A.L. vs C.O.A.L.

    I'm going to work up some loads with Barnes TSX. Barnes load data uses C.O.A.L while some other load data sources give over all length. Discrepancies are in thou., but I'm wondering what the C. is. Cartridge Over All, Completed? Can anyone enlighten me?

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    Moderator hunt_ak's Avatar
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    I believe they are the same and interchangeable...

    Over All Length
    Cartridge Over All Length

    I could be wrong, though...

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    Default Length

    Only real important thing - unless you are loading for others - is to make certain the rounds will relaibly feed through the magazine and chamber O.K. in your rifle.

    In general seating the bullet out as far as possilbe will give better accuracy and less pressure.

    Quote Originally Posted by ytlogger View Post
    I'm going to work up some loads with Barnes TSX. Barnes load data uses C.O.A.L while some other load data sources give over all length. Discrepancies are in thou., but I'm wondering what the C. is. Cartridge Over All, Completed? Can anyone enlighten me?
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    I have had best results with TSX's loaded between .075 and .125 off the lands. I have had great results with Match Kings close to the lands but not Barnes.

    The COAL versus OAL is the same thing. Keep in mind that the number in the manual is for their test barrel and chamber. It won't produce your best results unless you get very lucky.

    Both compressed loads and loads with the bullet touching the lands can produce high pressures. One versus the other can't be generalized in one direction.

    Start with minimum load data and work up towards max looking for best group. Take the load that looks good and vary the seating depth .025 and .050 each side of the recommend COL. If you have ogive measuring equipment start at .025 off for initial Barnes loads. Step out in .025 increments after you find your best charge and you will find your sweet load.

    Just curious, what rifle are you loading for and what components are you using?

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    I will be loading these for .270win. I will be using 140 gr. TSX, H4350, Federal large rifle primers and either Winchester or Federal brass, mostly fired once, some more times and all full length resized. I have a tang safety Ruger 77 and a Husky. As tvfinak says, most important is that the load will feed and chamber and in my case for both rifles. My daughter or wife will typically carry one when we are hunting and for our purposes, optimum usability is more important than maximum accuracy.
    I haven't loaded any Barnes bullets before and I understand that the spec's are different than jacketed bullets. Barnes also says that the ogive is different on the present bullets compared to earlier x bullets. I don't have a Barnes book, but they have good load info on their website and that's what I'm figuring to use. Their COAL is less than the minimum OAL in my Lee book and the COL from Hodgdon, for jacketed bullets. That set me to pondering about terminology.

    My question seems kind of academic, but I start to wonder about the use of different acronyms, meaning the same thing, in a practice that strives for precision.

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    Member marshall's Avatar
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    H-4350 will be just fine in the 270Win. Full length resizing is conservative but safe. If you have the tools to measure the distance from the head to the mid way point on the shoulder of fired brass from each rifle I would adjust the dies for a .002 shoulder bump on the shortest one. That would allow for chambering in both rifles and reduce brass wear.

    After sizing all your brass and trimming to length, perhaps 2.530" weigh 10 of each brand of case to get an average weight. I'm guessing here but I would say the Winchester will weigh less than the Federal. Do your load testing with the heavy brass. That will assure your powder charge will fit in both brands. Heavy brass of equal size and prep means less room for charge.

    "My question seems kind of academic, but I start to wonder about the use of different acronyms, meaning the same thing, in a practice that strives for precision."

    No big deal:

    COAL = cartridge over all length
    OAL = overall length

    It's obvious what they are talking about. The loaded round is a cartridge. The overall length is a measurement of the finished product. The precision comes from many other areas. IMO you get the most accuracy from case prep, powder charge and consistency.

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    Thanks for your replies. I kind of figured that was what the C was about, but not sure. I have a few more things to work with now.

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    In general, COAL/OAL for a magazine-fed bolt action rifle is defined by that particular rifle's magazine length and by where the rifling starts (throat). Don't pay attention to any sort of published COAL for magazine fed bolt action rifles.

    Another general rule - for accuracy and consistency with cup/core bullets, seat them at a depth to where they "kiss" or nearly touch the rifling - maybe 0.010" to 0.020" for starters. Different rules apply for barnes monolithic bullets - they like 0.050" +/- 0.020".

    It may not be possible to seat the bullet out that far and have it fit in the magazine. This is a potential issue for most any short action chambering with bullet diameter >6.5mm.

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    My understanding is that the OAL(COL,COAL) is the minimum measurement required to ensure safe pressures. That's pretty much what I wanted to confirm: that all of the terms meant the same thing. Barnes site has excellent information about reloading their bullets and they do say to seat for a freebore of 0.030 to 0.070, starting at 0.050 and working either way to the optimum for the rifle. As you say, my hunting round OAL can't be longer than what will fit both rifles.

  10. #10

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    Quote Originally Posted by Vek View Post
    In general, COAL/OAL for a magazine-fed bolt action rifle is defined by that particular rifle's magazine length and by where the rifling starts (throat). Don't pay attention to any sort of published COAL for magazine fed bolt action rifles.

    Another general rule - for accuracy and consistency with cup/core bullets, seat them at a depth to where they "kiss" or nearly touch the rifling - maybe 0.010" to 0.020" for starters. Different rules apply for barnes monolithic bullets - they like 0.050" +/- 0.020".

    It may not be possible to seat the bullet out that far and have it fit in the magazine. This is a potential issue for most any short action chambering with bullet diameter >6.5mm.
    They give this dimension to assure it will fit in all magazines for different manufacturers, col is is simpely a standard loaded length that will fit all manufacturers gun's, it in know way is probably close to optimum for any gun?

    As Vek said you can customize this length by varying seating depth to find where your particular rifle likes the ogive, (the place on a bullet where it's diameter starts to engage the rifling), some into the lands a few thousand's to backed away a few, ONE SHOULD MENTION AT ANY DEPTH YOU SHOULD START WITH A REDUCED CHARGE, you can increase pressure by seating deeper in the rifling, the opposite can be true also, there is a possibility to raise pressure by seating deeper in the case, hope that helps.

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