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Thread: A Couple of Quick OAL Questions

  1. #1

    A Couple of Quick OAL Questions

    Hello chaps,

    I'm working on my first reloads having finally received powder and bullets enough to get started. I'm working on a couple of ladders to look for pressure signs and find out what's safe in my rifle. After that, I'll load smaller variations around whatever looks promising and test for accuracy.

    At present I don't have a gauge to seat bullets by the ogive / position in the throat - I know that's a better way than OAL but I can't afford the tool right now. Therefore I'm using minimum OAL figures in the data to determine seating depth.

    For .308 Win I've got data that shows a 110gr Barnes TSX Flat Base bullet with a minimum OAL of 2.690".

    I actually want to load a 110gr Hornady SP which is also flat-based, but shorter than the Barnes bullet.

    The Barnes bullet is 0.955" in length. The Hornady bullets are 0.820" in length (average).

    Is it therefore reasonable to calculate the minimum OAL for this load by finding the difference in length and subtracting it from the Barnes minimum OAL, which should put the base of the bullet in the same place for the Hornady SP load?

    (0.955" - 0.820") = 0.135"
    2.690" - 0.135" = 2.555" = minimum OAL for Hornady 110gr SP?

    In case any of this is relevant:

    • in the absence of an accurate chamber / throat measurement for my rifle, I'm using the minimum OAL from the data plus 0.025" to err on the side of lower pressure. In this case, I plan to load to an OAL of 2.580".
    • I'm going to load H335 in 0.5gr increments from 47.5-52.5gr and stop firing when I see pressure signs. The data for the Barnes 110gr bullet is on page 363 of the Lee manual.


    Second question is related to the above - does anyone think there's anything stupid about loading to just above the minimum OAL when I don't have the information I need to load using distance from the ogive to the lands? Is the listed minimum + 0.025" a reasonable figure to use?

    Thanks in advance for any insights anyone can give - this is a new rifle and I'm new to reloading, so I'm trying to play it safe.

    Adam.
    Last edited by neutron619; 12-01-2014 at 20:26.

  2. #2
    Congratulations! You got it 100% right.
    There was a time -back when I began reloading and before- that seating depth was the mark, not OAL. This is what you have correctly deduced. ~Muir

  3. #3
    Well Muir is the authority for sure, and has given me sound advice in the past. All I'd say is why not just make a dummy round up with a lightly crimped throat and find your max col for that bullet in your chamber. FYI the listed max OAL for a 110gr hornady sp #3010 as 2.690.

  4. #4
    +1 to Woodmaster.

    I stopped worrying about getting close to the lands some years back and now Lee factory crimp my loads with the base of the bullet level with the top of the case shoulder.

    However, with a new or unfamiliar rifle, I chamber a loosely crimped round, first having smoked or magic markered the bullet. This, when gently extracted, shows me where the ogive first touches the rifling.

    Last time I did this I found that a "new to me" .22-250 had a much shorter chamber than anticipated.
    "Nonsense! They couldn't hit an elephant at this dista.....................".

  5. #5
    You'd think a 110 grain in a 308 would fall out of the case before getting close to the lands. If you are curious though, and have a cleaning rod with a flat tipped jag, you can do this; Put the bolt in the gun and cock it on an empty chamber. Run that rod into the bore til it stops at the bolt face. Carefully place a pencil mark on the rod at the muzzle. Remove the rod. Remove the bolt. Drop a bullet (projectile) nose-first into the chamber push it gently into the leade with the rod. Put the rod back down the bore til it touches the bullet nose. Again carefully mark the rod at the muzzle. Remove the rod. Measure between marks with a vernier. That's the max OAL you can have -or close to it.

    Seat deep. Forget the lands! ~Muir

  6. #6
    Quote Originally Posted by Muir View Post
    You'd think a 110 grain in a 308 would fall out of the case before getting close to the lands. If you are curious though, and have a cleaning rod with a flat tipped jag, you can do this; Put the bolt in the gun and cock it on an empty chamber. Run that rod into the bore til it stops at the bolt face. Carefully place a pencil mark on the rod at the muzzle. Remove the rod. Remove the bolt. Drop a bullet (projectile) nose-first into the chamber push it gently into the leade with the rod. Put the rod back down the bore til it touches the bullet nose. Again carefully mark the rod at the muzzle. Remove the rod. Measure between marks with a vernier. That's the max OAL you can have -or close to it.

    Seat deep. Forget the lands! ~Muir
    Who bought you a pencil, what happened to the clothes pegs .

    John
    A clever man knows his strengths, a wise man knows his weaknesses

  7. #7
    Quote Originally Posted by JAYB View Post
    Who bought you a pencil, what happened to the clothes pegs .

    John
    Keepin' it simple, Cuz.~Muir

  8. #8
    Hi Chaps,

    Just wanted to say thank you to you all for the confirmation of my approach and the suggestions. Nice to know that approaching things logically is ok and that there aren't too many "hidden factors" I haven't read / learnt about. I'll go with my instincts for now and use that as my starting point - I've got the rest of my life to make improvements after all!

    Thanks again,

    Adam.

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