Measuring max CASE length for your rifle

Discussion in 'Reloading' started by RoughNeck182, Jan 21, 2010.

  1. RoughNeck182

    RoughNeck182 Member

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    Recently I was given a box of nearly 100 handloaded rounds for my factory Rem 700-V .243 but upon inspection I found that the cases themselves were a few thousandths over the max length. Now, not wanting to pull all the bullets and trim them all I searched the net about case length. I came across a method where you size a case then cut the neck off about 2/3 down to the shoulder and seat a bullet in whats left of the neck, then use the cut off portion as a sliding collar so that you can test where your case neck bumps the small chamber constriction before the freebore or lands area begin (I don't know any proper terminology for this portion of the chamber). Anyway, I did this test a pile of times and made more than one of these gauges and am confident in the conclusion as it's totally repeatable: that my case necks don't contact the constriction until over 30 thousandths past the max case length! Now, some sources I've read online say this is pretty normal. How many of you guys have done this same testing and found such a big gap?? I would like to keep my cases about 10 thou from the 'constriction' to reduce errosion and get my 75 gr V-Max's out to the lands with more bullet in the neck... it seems straightforward but am I missing something here, playing with fire so to speak? Why is there so little talk about this chamber dimension but so much about the distance to the lands; is it just because it's not so much accuracy related as the lands-to-ogive distance is?

    Thanks for any feedback!!
    John
     
  2. Johnboy

    Johnboy Well-Known Member

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    you are good to go.some guys with match chambers like to trim off about .005 from the chamber.so I would use the rounds and keep loading them.

    and for what its worth to yea.I use this meathod of measureing my chamber.for me why by a tool when you can make one.and with reloading we always have brass of some sort that we are not going to use.and this way you do not have to pull the pug out to use it on another chamber.this way you can keep it and always have the little jig on hand.
     

  3. RoughNeck182

    RoughNeck182 Member

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    Thanks Johnboy, glad I don't have to pull all these rounds and won't have to trim so much. Wish I had made one of these months ago! :)
     
  4. Stormrider

    Stormrider Well-Known Member

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    I don't believe that you are measuring the case length of the chamber with this method. If you use a bullet you are measuring the length of the chamber to where the chamber narrows to the diameter of the bullet. That is not the same as measuring max length of the case.
    If you look at the tool that Sinclair sells you will see that it has a lip on it that is the same diameter as the case. So when it contacts the chamber wall that is the same place that the cartridge case will contact it.
    I'll admit that there is not a lot of difference, but if you are going to be precise about you handloads...
     
  5. RoughNeck182

    RoughNeck182 Member

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    Stormrider: You are thinking of the gauge where the bullet is seated long and loose enough to slide in the neck, and it contacts the rifling to give you a measure of CARTRIDGE Over All Length for chamber. The gauge I am talking about the bullet is seated to NOT contact the rifling, and is seated tight enough not to move in the neck. The case NECK is cut about 2/3rds of the way down to make a sliding donut collar that slides on the bullet itself so that the CASE length is 'adjustable' (the length from the base of case to the top of the neck donut/collar. You can move the donut/collar out further on the bullet so the case neck is extra long and it will bump the chamber wall as you pointed out, and get slid back. This sliding piece of neck is the equivalent of the part of the sinclair tool that is the same diameter as the case as you pointed out. After you've chambered this gauge, then you know how long the case is when it will bump the chamber. Check out the "POOR MAN'S GAUGE" at Varmint Al's Handloading/Reloading Page for a description of how I made mine.
     
  6. jmden

    jmden Well-Known Member

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  7. Johnboy

    Johnboy Well-Known Member

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    thanks roughneck for pointing that out for me.seems that someone has deleted some of my post.been useing this way for a long time and it works all the time for me.
     
  8. Stormrider

    Stormrider Well-Known Member

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    Thanks, Roughneck. I didn't understand exactly what was said in the first post. I went back and reread it and now I understand what you were saying.
    I also don't think you're missing anything.
    I have rifles with a 0.040 longer than spec neck length. In fact, the shortest one I have is 0.020 over. So I don't worry about neck length except to keep the cases relatively close together for consistency.