Hornady OAL gauge & .30-06

Discussion in 'Reloading' started by glockrod, Mar 9, 2014.

  1. glockrod

    glockrod NRA-Endow. Life

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    I just recently invested in this gauge.

    I am having a little trouble understanding exactly what the measurements may mean about my chambers/throats other than the obvious that I need to load a little shorter than these measures and no more than max COAL.

    All these measures were made with calipers with the bullet in the Hornady modified case. The bullet is a 168gr hpbt:
    Springfield M1903: 3.317"
    HRA M1 Garand: 3.386"
    Browning A-Bolt: 3.300"

    What do these measures mean in regard to my chamber/throats?
    If my understanding is correct, the M1 appears to show some throat erosion. Other than that, the 1903 and Abolt are shorter than the max OAL given in several manuals. Now, I know that the manual's given OALs are just what was tested in that particular gun, but what does that mean for both of these guns having shorter max lengths?

    I never realized how useful this tool could be as I would hate to have loaded a bunch of rounds that exceeded these measurements.
     
  2. F106 Fan

    F106 Fan

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    Pretty much just what it shows: the chamber varies all over the place. I'm surprised the A-Bolt is that tight but it's not a problem because Sierra says to load the 168 gr HPBT to 3.285" which would leave 0.015" to the lands. There's quite a jump in the M1 but a brand new Rem 700 in .308 has more jump than that. The chamber is just cut deep.

    If the 1903 shoots pretty well, I might run the bullet out a bit. I'm not a big fan of the 'load them long and let the chamber seat the bullet' approach but it is used by bench rest shooters. You really need to be careful with the load if you get the bullet too close to the lands.

    Not necessarily although it is worth looking at. My brand new Rem 700 has more jump than that with a 175 gr HPBT.

    I'm not sure where your data came from. As I said, Sierra recommends 3.285" for the 168 gr HPBT. I use Sierra for all my rifle data since I use their bullets.

    It's quite useful to know how the bullet sits in the chamber. The problem is, many times there is nothing you can do about it. If I try to load the 175 gr HPBT to get close to the lands in my Rem 700, the bullet won't be held in the case mouth. Now what? Oh, I suppose I could have the barrel shortened and the chamber recut but since the thing routinely shoots 1/2 MOA or better, maybe I should leave well enough alone. After all, the load and rifle are far better than I am.

    Richard
     

  3. glockrod

    glockrod NRA-Endow. Life

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    Thanks for that input Richard.

    Having a measuring device only works well if you know how to use that info. Once I got the measures, I was still left not knowing what they mean. Having your input tells me that I am likely in the ballpark with the throats. The important thing is how well they shoot.
    On that note, I know the A-Bolt shoots about 1 MOA with my handloads. I just got the 1903 and I have only shot the M1 for fun so far without an official sight-in. I will be working up loads for each, but now I know how to load them and whether I need to segregate the loaded rounds for use in a specific gun.
     
  4. cheygriz

    cheygriz God Bless Trump

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    I use the older Sinclair guages. Most of my rifles have their "sweet spot" about .005 off of the rifling.

    But that varies. On an old Sako Finnbear 7MM magnum, the "sweet spot" is .020 off of the rifling. There's no substitute for experimentation.:supergrin: