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Thread: First time using OAL gauge.

  1. #1

    First time using OAL gauge.

    Got myself a Hornady OAL gauge at the Deer Stalking fair on Sunday. Never used one before.
    I started by doing trial measurements to get used to using it. This was obvious by results varying by .009".
    After I was getting measurements with less variation (.004"), I started 22 measurements. I removed the highest and lowest leaving me 20 measurements which I averaged.
    The result for my .243 was an OAL of 2.668".
    Beforehand I had been seating to 2.700" so the head must have been into the lands by
    I had previously worked up a load to max with no over pressure signs although the best accuracy node was a relatively soft load.
    I'm going to seat .010, .020, .030 and .040 below the 2.668" to find the best grouping.
    Does this all sound ok and can I, once finding the best OAL, then start on working up the load again to find a slightly higher velocity load as at the moment velocity is at 2780fps.
    Any advice appreciated.

  2. #2
    What bullet and powder are you using? Sounds a bit slow for 243 full chat loads unless your bullets are over 100 grains.
    Your theory is ok - pushing the bullet further in will have a similar effect to increasing the powder load. It will raise velocity & pressure.
    I'd go the other way increase the charge first with the bullet at least 20 thou off the lands & then try progressively deeper seating.
    Definitely get the bullets away from the lands - I've seen some nasty pressure spikes caused by tight neck tension 243 when rammed into the lands.
    Best (safest) to keep well clear - bullet jump is not as important as many think. Consistent & firm neck tension is more important!
    I like the Lee Factory Crimp Die - it really does work well & usually improves consistency & tightens groups.


  3. #3
    How did you measure the loaded rounds before? On a vernier to the tip of the bullets or with a guage to the ogive of the bullet. This may be the reason that you didn't experience any problems (if measured to tip). Just my thoughts...

  4. #4
    Sierra 85gr HPBT over 36.5gr IMR4064.

  5. #5
    Hi Phitt
    IMR data indicates COL of between 2.610" & 2.635" for bullets in your weight range (80 - 90 grains) so you are possibly a bit long although your bullets are HP so may be a bit longer than the ones listed online - I doubt it though because the listed 85 grain Barnes TTSX is a long for weight bullet.
    Sooooo your low velocity is probably/possibly due to the bullet seating being long.
    You say you aren't getting signs of high pressure - Are you getting sooty case necks after firing? If you are the pressure is low & you can go up a bit if that is your aim.
    I know that velocity is not the ultimate requirement but there is room for improvement - 243 with 85 grains should be running at about 3000 ft/sec before pressure signs appear.
    My previous post is still valid I feel based on the evidence & is probably a good indication of the way to go. (Watching for all pressure signs as usual & changing only one parameter at a time).
    You are basically starting your load work up again with the bullets away from the lands so treat it as such.
    The Hornady OAL gauge is a bit awquard to use but after practise it gets easier to get repeatable results - persevere & you should get there (wiggling the gauge as you gently feed the bullet up to the lands helps) . Measure bullets to the ogive rather than to the tip when actually loading - the COAL is not as accurate when measured over the bullet tip. I only use it as a guide of starting point then disregard it - I measure my own rifle, stay well away from the lands & work in a sequence that builds pressure as the load is developed as I've already indicated.
    Have fun


  6. #6
    I found a length variation of +/-
    .002" in a sample of 30 HPBTs. I did a good few test measurements to get used to the gauge before I was happy with the consistency of my measurements. I did find the slide a bit sticky to start with but got the hang of it eventually.
    Just what I thought, starting to work up again. Cheers for your input.

  7. #7
    SD Regular teyhan1's Avatar
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    Try some marker pen around the ogive of your old rounds and gently feed into rifle. If they are touching the lands you should see it on the extracted round.
    “Man surprised me most about humanity. Because he sacrifices his health in order to make money.Then he sacrifices money to recuperate his health. And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived.”........Dalai Lama

  8. #8
    Sell the damn thing on Ebay and quit chasing your tail.
    Load to recommended OAL and be happy.~Muir

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