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Thread: Measuring COL with deprimmed sized case

  1. #1

    Measuring COL with deprimmed sized case

    Following on from several comments on here prehaps some off our very experienced reloaders may reply to this.

    Further to my issues in trying to get accurate and reproducable COL for my .223 69 TMKs i made up a dummy round and used the marker pen method.

    To achieve this I had to slightly enlarge the neck dia to get the bullet to fit, it was snug. I read on here that all you do is place a bullet in resized, de primmed case and load, obviously it will be stiff. How do you do this if the bullet will not go into the case neck in the first place?

    I have brand new Lapua match brass or FL resized lapua brass.

    Also if you use the above method and the bullet is forced into the leade/lands how do you know if the bullet was cleanly pulled out when you eject the case, it might have been pulled fractionally out of the neck as the bullet was extracted?

    Comments please.

    D

  2. #2
    I think it's easiest to cut the case neck like this:

    http://bulletin.accurateshooter.com/...o-lands-gauge/

    It requires too much force to seat a bullet in a resized case, and there's a risk of the bullet being pulled out on extraction.

  3. #3
    Quote Originally Posted by Cyres View Post
    Following on from several comments on here prehaps some off our very experienced reloaders may reply to this.

    Further to my issues in trying to get accurate and reproducable COL for my .223 69 TMKs i made up a dummy round and used the marker pen method.

    To achieve this I had to slightly enlarge the neck dia to get the bullet to fit, it was snug. I read on here that all you do is place a bullet in resized, de primmed case and load, obviously it will be stiff. How do you do this if the bullet will not go into the case neck in the first place?

    I have brand new Lapua match brass or FL resized lapua brass.

    Also if you use the above method and the bullet is forced into the leade/lands how do you know if the bullet was cleanly pulled out when you eject the case, it might have been pulled fractionally out of the neck as the bullet was extracted?

    Comments please.

    D
    Unlikely to be fractionally pulled out; measure before and after to reassure.

    You need to chamfer the inside of the necks to ensure the projectile goes in, or use a Lyman M die.

    the other method is use a cleaning rod (although aware some on here might not even own one...) with brass jag attached, and carefully push it from the muzzle end to meet the EMPTY CHAMBERED closed bolt face. keep pressure on rod against bolt face and put tape round rod at muzzle - be accurate.

    put projectile into chamber and push forward with a breechstick so it engages the lands.

    repeat rod guide intobarrel from muzzle slowly until you touch but dont dislodge the projectile. measure the gap between crown of muzzle and the tape from earlier = length of overall round with bullet into the lands. Make dummy round to the same length using the SAME projectile and back it off, say 20thou and you probably have a winner. test and repeat.

  4. #4
    Quote Originally Posted by Cyres View Post

    Also if you use the above method and the bullet is forced into the leade/lands how do you know if the bullet was cleanly pulled out when you eject the case, it might have been pulled fractionally out of the neck as the bullet was extracted?

    Comments please.

    D
    I've used the felt tip pen method over the years and have never had a problem with this.... if you use enough felt tip then you'll get a tell-tale ring of clean copper if the bullet has been snagged on extraction.

    On the grounds that I just neck-size until fired cases won't chamber..... I use a fired case that chambers and gently put a flat in one side of the neck by pressing it on the bench..just enough to grip the bullet... the felt tip ink won't run under the case neck.

    I'm assuming you're using a comparator on the bullet's ogee to measure the seating depth... a comparator is one of the more useful bits you can buy.... consistency is key.

    Cheers

    Fizz
    Last edited by fizzbangwhallop; 27-01-2016 at 16:00.

  5. #5
    Try making one of these: I used aluminum blocks fit tightly to a steel rod with a flat end on the rod. (a cleaning rod for illustration) slip the rod down the bore of an unloaded, cocked rifle up against the bolt face. Slide both blocks up against the muzzle. Tighten set screw in part "B". (the rear block)

    Remove bolt, slip a projectile into the throat and lightly hold it into place with another short section of rod. Slip the long rod assembly down the bore until the end contacts the projectile tip. Slide block "A" against the muzzle and tighten set screw. The distance between the blocks is your max COL. Need less to say, the precision of the results are as precise as the build.

    Frankly, I only use it for setting the seating depth of cast bullets which perform best snugged into the rifling. I never use it for jacketed bullets unless there is a question as to whether a loaded round made of a bullet of unlisted COL will chamber.~Muir




  6. #6
    Gentlemen,

    Thanks for the detailed replies, I will try the cut neck method first. And yes I only work off ogive measurement.

    Thanks to you all

    D

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