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Thread: Best way to measure OAL

  1. #1

    Best way to measure OAL

    Hi
    Got the reloading bug but having difficulties measuring the Overall Length. Used a brass rod with machined stops. all manufactured to the highest standards. 1 Push the brass rod into Rifle until it touched the closed bolt.2 Slide stop to point of barrel and secure. Drop bullet head gently into the chamber (80 grain Nosler ballistic tip) push head gently into the rifling (with Calibrated Chop Stick) push gently with the brass rod Bullet Head chop stick using feel to find the point of contact secure second stop against point of barrel measurements taken with digital Vernier calipers but not conclusive to many variations. any ideas


    Thanks in advance Angus

  2. #2
    Quote Originally Posted by salmon_fisher View Post
    Hi
    Got the reloading bug but having difficulties measuring the Overall Length. Used a brass rod with machined stops. all manufactured to the highest standards. 1 Push the brass rod into Rifle until it touched the closed bolt.2 Slide stop to point of barrel and secure. Drop bullet head gently into the chamber (80 grain Nosler ballistic tip) push head gently into the rifling (with Calibrated Chop Stick) push gently with the brass rod Bullet Head chop stick using feel to find the point of contact secure second stop against point of barrel measurements taken with digital Vernier calipers but not conclusive to many variations. any ideas

    Angus


    Thanks in advance Angus
    A few of the bench rest shooter I shoot with use the method you describe to great effect but I couldn't get it to work for me. I just couldn't consistently get the bullet to 'just make contact' with the rifling.

    I use a Hornady Lock n Load OAL guage and comparator along with the correct modified case. Makes very light work of finding the lands and gives accurate results. Also works on the OGIVE rather than overall projectile length as it is this that is being 'jumped' not the tip of the bullet!

    Paul

    Modified Cases here - http://www.jjkshootingsupplies.co.uk...-0-0-0-0-0-0/1

    Hornady OAL guage on ebay here - http://www.ebay.co.uk/itm/Hornady-Lo...item2a1ba60a71

    Hornady Bullet Comparator here - http://www.opticswarehouse.co.uk/pro...26+Micrometers

  3. #3
    I have often wondered about this on old vs new rifles.

    I have seen a borescope of an old rifle and none of the lands ended (or began) at the same level through bore wear or burning/metal crazing.
    to do this on a new crisp barrel with sharp cut throat would work, but to try to measure accurately with a vernier where the lands start on an old rifle must be a bit like measuring the surface area of a crinkle cut crisp!

  4. #4
    Actually I believe your solution is "looking for a problem". As yet I simply check Overall length just as it it is I place the digital calipers across the Head of the cartridge case and the opposing jaw across the tip of the bullet. I check about 1 in 5 or 1 in 10 depending on the size of the batch being loaded.

    I am not interested in bench rest competition, if I wanted to use a "rifle" that weighs the same as a piece of coastal artillery I am sure I could find a way though.

    Then to those who "claim" to seat 0.002" off the lands I wonder how often you re-check the measurement to keep it thus as the smallest bit of wear will alter you precious jump amount.

    For my sins I have found that all my rifles shoot well with a large jump, in fact to get teh 7mm Hornady 139 Grn BSTP to group under MOA I had to seat the bullet much deeper in the neck and ended up with them seated to that the crimping ring on the bullet of the bullet was only a tad outside the neck. Seated with the ogive close to the lands in a rifle that had only shot about 200 rounds from new produced groups closer to 2" than 1" at 100 yards.

    Another case that made me stop and think and then question the small jump mantra we see chanted/quoted all the time.

    It was a similar process which made me question the "free floating barrel" mantra as well.

  5. #5
    Quote Originally Posted by Brithunter View Post
    Then to those who "claim" to seat 0.002" off the lands I wonder how often you re-check the measurement to keep it thus as the smallest bit of wear will alter you precious jump amount.

    For my sins I have found that all my rifles shoot well with a large jump, in fact to get teh 7mm Hornady 139 Grn BSTP to group under MOA I had to seat the bullet much deeper in the neck and ended up with them seated to that the crimping ring on the bullet of the bullet was only a tad outside the neck. Seated with the ogive close to the lands in a rifle that had only shot about 200 rounds from new produced groups closer to 2" than 1" at 100 yards.

    Another case that made me stop and think and then question the small jump mantra we see chanted/quoted all the time.
    With my old Tikka T3 6.5x55 I got the same accuracy out of Federal Powershoks as I did out of my homebrewed handloads.. the home loads were jumping 20 thou, the feds about 1/4"!!!!! so that holds up what you are saying as a truism..

    On the other hand, my .308 Sako TRG, Likes em close. I run them 20 thou off the lands and the group noticably opens up the further back you go, although, it could be that if I kept going I would reach a big jump which was as consistent.

    Good point re checking regularly if you are going down this route though, throat erosion will constantly increase the jump!

  6. #6
    I use this method.



    Works very well.

    In simple terms my normal method for working out the best jump is to set the OAL to book length with a mid point load, then if that's not good enough group wise, increase the length a bit for the next load.

  7. #7
    Quote Originally Posted by salmon_fisher View Post
    Hi
    Got the reloading bug but having difficulties measuring the Overall Length. Used a brass rod with machined stops. all manufactured to the highest standards. 1 Push the brass rod into Rifle until it touched the closed bolt.2 Slide stop to point of barrel and secure. Drop bullet head gently into the chamber (80 grain Nosler ballistic tip) push head gently into the rifling (with Calibrated Chop Stick) push gently with the brass rod Bullet Head chop stick using feel to find the point of contact secure second stop against point of barrel measurements taken with digital Vernier calipers but not conclusive to many variations. any ideas


    Thanks in advance Angus
    Yeah. Stop worrying about it! Generally, I do what Cooter suggests. ~Muir

  8. #8
    salmon fisher, i have been using the same method as you for years now and have no problems at all i just reckon its a matter of feel, i seldon get variaitons of more then .002".
    I then make a dummy round using the same bullet and take all my measurements from that using a bullet comparator measuring from the ogive.

    Ian.

  9. #9
    Salmon fisher, as folks have said, don't worry about it too much. Assuming your rifle has a magazine, try an experiment with some dummy rounds made up the way Cooter, Muir and Whitebeard have suggested. Make these to the maximum length that you can feed into your magazine which will then easily cycle through your rifle without any feeding problems. The OAL length of those dummy cartridges is the maximum length of cartridge that you can use in that rifle with that bullet if you ever need a quick second shot for a wounded deer. You will generally find that this is less than the maximum OAL. You obviously then adjust the OAL to get the best grouping. You can, when establishing maximum OAL, also use candle black or a felt tip pen to coat the bullet in the dummy cartridge and be able to observe the faint marks the lands will leave when the bullet touches them. Reduce the OAL until there are no rifling marks. Obviously don't put primers or powders in when making up dummy rounds and don't apply heat to live cartridges! I'm sure you wouldn't but who knows who might be reading this thread!

  10. #10
    Hi Bob
    Thanks for the tip I have been in touch with Dingwall Dave who also suggested the Candle tip used on a round with no primer or powder but ommitted not to use a heat source on Live round You can never be to careful thanks for bringing it up !! I did try the method using the brass rod and stops x10 and took an average, but maybe just maybe the bullet head was not sitting correctly, was considering putting the bullet head into a re-sized case extending it well out then it should enter the rifling square it does come to a definate stop when coming up to rifling but the varied results say different all I can think is it the head is not coming square will if attached to a dummy case.


    Thanks in advance for all assistance Angus

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