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Thread: Coal

  1. #1

    Coal

    I've loaded some rounds for my tikka 243 for fox this coming harvest. I tend to shoot a 70gn nosler in the summer months because I find it gets though the stubble better than the 58gn vmax. I'm using varget at 41 gn and I'm getting an inch group at 200m . ogive is 20 though off the lands, I've never dabbled with changing round length. Will it improve the accuracy? I don't post very often so be gentle

  2. #2
    Quote Originally Posted by wag View Post
    I've loaded some rounds for my tikka 243 for fox this coming harvest. I tend to shoot a 70gn nosler in the summer months because I find it gets though the stubble better than the 58gn vmax. I'm using varget at 41 gn and I'm getting an inch group at 200m . ogive is 20 though off the lands, I've never dabbled with changing round length. Will it improve the accuracy? I don't post very often so be gentle
    It's a good question. I would try 40.8 gr, 41.0 gr and 41.2 gr to see if you can gain any benefit by tweaking the powder first. If 41.0 gr is your best powder load, then I would try seating the bullet deeper in 5 thou increments.

    Keep in mind that you are the man on the spot. Other things that can help group size include, having a consistent consistent shooting position, a target optimised for your scope reticle, to name a couple.

    Best regards

    JCS

  3. #3
    Quote Originally Posted by jcampbellsmith View Post
    It's a good question.
    It's only a good question if:
    a. You actually need better accuracy than 1" at 200m or
    b. You'd like to have a play-about that might improve the (already outstanding, IMO) accuracy, but will certainly result in consumption of time, components and barrel-life.

    If it is a good question, then JCS seems to be about on the money.

    Last edited by Dalua; 29-06-2015 at 20:29.

  4. #4
    Quote Originally Posted by wag View Post
    Will it improve the accuracy?
    How the heck would we know?
    I'm with Dalua on this one. An inch at 200 begs the question "Why?" ~Muir

  5. #5
    Because I'm interested And never done it. In your experience Muir has it made any of your rifles more accurate. There must be a point where a factory rifle set up cannot be improved. Have I reached this. No harm in trying to make something better. I don't have a garage full of every caliber known to man. I have the time and interest to concentrate on the small number I do have

  6. #6
    The benefits (or otherwise) of playing with the COAL depend principally on two factors, bullet design and chamber throat / freebore. Taking the latter first, some factory rifles are notoriously over-throated these days as an anti-litigation measure in the USA. This can result in substantial bullet jumps at SAAMI / CIP standard COALs and extending the COAL in handloads (to reduce bullet jump) may bring benefits assuming that the bullet shape / length allows shallower seating, and/or the magazine length allows this or the rifle is to be single loaded.

    On the other (bullet) side of the equation, most sporting bullets and many older match designs have relatively short tangent-form ogive front ends that are exceedingly jump tolerant. Basically, they'll accept anything from barely out of the lands to a 100 thou' jump or more. Some (mainly Hornady designs) have a mild secant shape nose and they're a little less tolerant, but are still easily tuned at normal COALs and including a substantial jump using powder charge variation alone.

    Then there is an increasing number of mainly Berger models that can sometimes in some cartridges / rifles be flexible, but more often than not are very jump intolerant, or more precisely very jump specific. This applies primarily to VLD types which have long noses in what's referred to in the ballistic / bullet design trade as 'aggressive secant nose forms, this including Berger 'Hunting VLDs'. The norm is to either 'jam' them or jump a lot, a 'lot' starting at 40 thou', but sometimes double or treble that before they perform at their best. A jammed bullet isn't a great idea in a field rifle usually, so it may involve tuning the load using some seriously large jumps. The newer Berger Hybrid match design is supposed to overcome these issues, but in some calibres / chambers seems to need to be treated as a VLD.

    Barnes solid copper types are also recommended for experimentation with large jumps.

    Since you're using a conventional tangent ogive lead core jacketed type and also getting much better precision than you paid for with a factory rifle, I'd support the JCS / Muir views of leaving well alone. At 20 thou' jump, you're in an ideal situation with these bullets - this type usually performs very well in the 10-20 thou' jump range. Don't go below 10 thou' unless you are very confident about your COAL measuring tools and practices (the Hornady / Stoney-Point modified case system is very good but usually injects a few thou' error into the setting) and you have done a bullet BTO (base to ogive) check and if necessary batching job using a bullet comparator and callipers. The reason for all this is that trying to be too clever and precise with a smallish jump (like the 5 thou' 'out' some people quote) risks seeing variables produce a situation where some bullets just kiss the start of the lands and others make a small jump, usually a precision-wrecker.

    In fact if you do want to experiment, do a BTO check on your bullets. Most modern designs are good, but one sometimes still finds large variances within a single box. Two or three thou', even five thou' is neither here nor there for a deer rifle, although a long-range 'Match Rifle' or F-Class competitor will batch bullets in one/two thou' lots. If you're above five thou' variations you may see some benefit from measuring / batching - but to be honest I wouldn't place a large bet on that.

    With 243 Win usually quoted as having a 2,000 round barrel life, but very good accuracy falling off well before that figure, if you're getting a one-inch group at 200 yards, I'd use this rifle for its intended purpose only plus the minimal amount of use in practice, checking scope zero etc.
    Last edited by Laurie; 30-06-2015 at 09:36.

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