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Thread: 243 Bullet seating depth

  1. #1

    243 Bullet seating depth

    Hi guys,

    Just reloaded my 5 first 243 win on a my new rockchucker press

    Absolutely loved it, the precision of the gear and scales etc was phenomenal to behold, I was almost in awe.

    When seating the bullet heads I looked up the SAAMI OCL max which was 2.710". I could not find a recommended seating depth however,
    I have currently seated to 2.699" on all five, although I am under the impression I can seat them lower later if necessary.
    I just have a few questions,

    1) What is the recommended seating depth for the 243 win, and if different for each bullet how do I work it out ?
    2) On my bullet seating die its very fiddly / hard to move the top knob of the seater ever so slightly to 0.001" of an inch, is this hugely important or is there a limit that is acceptable ? eg 0.1, 0.01 or 0.001" ?

    I loaded some once fired Privi brass with 37.5gr of Ramshot hunter, loaded with Hornady Varmint 87gr BTHP heads and CCI large rifle primers.
    I used this as it is the same powder, primers and heads I loaded with my Lee Loader kit so know it should work safely, then I can start tweaking things.

  2. #2
    you need to work it out to the rifle you are going to be using. The cheap and easy way is to get a few fired cases from that rifle and a bullet head you are going to be reloading. then try the head in a few of the cases till you find one that is a snug fit but the head will move in and out. then put the head just in the case (not too far) then chamber it in your rifle and gently remove, measure the OAL do this a few times and that will give you the length to your lands. Start your seating depth 10-15 thou off the lands. you can play with you seating depth from there till you find the sweet spot.
    If you look on you tube there are plenty on seating depth.
    Hope that makes sense and helps

  3. #3
    Quote Originally Posted by Lloyd90 View Post
    Hi guys,


    I loaded some once fired Privi brass with 37.5gr of Ramshot hunter, loaded with Hornady Varmint 87gr BTHP heads and CCI large rifle primers.
    I used this as it is the same powder, primers and heads I loaded with my Lee Loader kit so know it should work safely, then I can start tweaking things.
    Did you mean to type 47.5 gr of Ramshot Hunter and not 37.5 gr?

  4. #4
    The tried and tested way is to seat the bullet so its base is at the same level as the base if the neck. You then load up different loads and see which works. You can either play with the load until you get one that groups or use the OCW method (look it up on here) which is the one I favour.
    Either way round be safe and welcome to a whole new facet of shooting.

  5. #5
    Quote Originally Posted by shendy View Post
    you need to work it out to the rifle you are going to be using. The cheap and easy way is to get a few fired cases from that rifle and a bullet head you are going to be reloading. then try the head in a few of the cases till you find one that is a snug fit but the head will move in and out. then put the head just in the case (not too far) then chamber it in your rifle and gently remove, measure the OAL do this a few times and that will give you the length to your lands. Start your seating depth 10-15 thou off the lands. you can play with you seating depth from there till you find the sweet spot.
    If you look on you tube there are plenty on seating depth.
    Hope that makes sense and helps
    I have always started my loads with the bullet actually touching the lands and found that the most accurate loads have always been touching[243] or nearly so[6.5/.30] in most rounds the only exception being both my 7x64 which need to be a frightening long way off!

  6. #6
    There are several ways to accomplish the task of determining the length of a round with the bullet touching the rifling. I have used most of them and found them to be satisfactory but my method, detailed below, makes the process easier and faster.
    It is possible to use a cleaning rod and a marking pen for this purpose but for those of you who want something more precise, here is my way:

    First, you will need a brass rod of about 5mm diameter and around 1 metre long. That’ll suffice for calibres down to 22 centrefire. Using a fine file, ensure one end is square and smooth and there are no sharp edges. You will now need two identical small metal blocks with true, square faces and drilled to fit easily on the rod. These blocks each have a thumbscrew so that they can be clamped to the rod. If you know of someone who is handy with a lathe, get them to make you two identical cylinders, drilled centrally with tapped holes for the thumbscrews at right angles to the central holes. The blocks(or cylinders) will slide on the rod and may be clamped appropriately with the thumbscrews. The thumbscrews should have flat, not pointed, ends and made so that only firm pressure can be exerted(don’t have them so that they mark the rod when tightened).
    To determine your maximum overall loaded cartridge length:
    1. Stand the unloaded rifle vertically, muzzle up, with the bolt in battery and firing pin cocked,
    2. Slide the rod into the barrel until it bottoms on the boltface.
    3. Slip the blocks down the rod until they both sit on the muzzle
    4. Tighten the thumbscrew on the TOP block
    5. Remove the rod and turn the rifle over so that the butt is upwards.
    6. Remove the bolt
    7. Carefully drop a bullet of the type you are going to use, nose first, into the action and very gently tap it down with a cleaning rod. You now have a bullet seated in the throat, touching the lands.
    NB - the word bullet here is used in its correct meaning and is the actual missile or projectile and NOT a “bullet” -which the uninformed like to call a loaded round or cartridge– make that mistake and you may have an accident waiting to happen.
    8. Reverse the rifle again so it’s muzzle is up and slide the rod down until it touches the tip(meplat) of the bullet. Be careful only to slide the rod slowly, if you tap the bullet tip, it’s likely to be knocked out and you’ll have to start again.
    9. Allow the bottom block, the one which was not clamped to the rod, to slide down and be seated on the muzzle
    10. Clamp in place with the thumbscrew
    11. Remove the rod and its clamped blocks
    12. Using your caliper, measure between the INSIDE faces of the blocks to get the maximum length of the loaded round with the bullet touching the lands.
    13. Repeat at least three times with bullets from the same box and average the results.
    14. Decide how far off the lands you want your bullet to be, deduct from the result obtained above and away you go.
    15. However - and there’s always however - if the loaded round, as determined above, will not fit in your magazine, you’ll need to reduce the overall length until it does. Additionally, there should be at least one calibre’s length of bullet in the neck for robustness in handling and consistent neck tension.
    As you can see, this technique is merely a refinement of the cleaning rod/marker pen method, but more precise.
    The measurement determined in this way is only valid for the bullet type used. If you use another make, weight or type of bullet, the measurement will have to be repeated using that bullet.
    You can, of course, load your ammo to the length recommended in the loading manual.
    Peter

  7. #7
    Or simply use reloading manual data.
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  8. #8
    Hi Peter, As per the load data with the lee loader I originally had, the 2.5CC scoop gives 37.5Grains of powder, which apparently gives a velocity of 2675.

    As this is what I reloaded before I did 5 the same and intended to work my way up. The data states the NEVER EXCEED as 45.5Grains (which should give a velocity of 3246).

  9. #9
    Quote Originally Posted by Lloyd90 View Post
    Hi Peter, As per the load data with the lee loader I originally had, the 2.5CC scoop gives 37.5Grains of powder, which apparently gives a velocity of 2675.

    As this is what I reloaded before I did 5 the same and intended to work my way up. The data states the NEVER EXCEED as 45.5Grains (which should give a velocity of 3246).
    I mention this as Quickload states that at 37.5 gr of Ramshot Hunter this will give only a 77.6% case fill, and only a 90% burn of powder and only 31,000 psi compared with a max of 60,000 psi and finally a ballistic efficiency of only 18% when one should be looking for a % nearer 30%. Mind you quickload is only a guide but even so this recipe appears to be on the very low side.

    Perhaps some one else with quickload will verify this.

    And... whilst writing I would wish to steer you away (as a new reloader) from the suggestion of seating your bullets in a factory rifle on the lands - better to seat the bullet at SAAMI and then alter the distance from the lands. A rifle can easily have several sweet spots.

  10. #10
    Quote Originally Posted by PeterH View Post
    I mention this as Quickload states that at 37.5 gr of Ramshot Hunter this will give only a 77.6% case fill, and only a 90% burn of powder and only 31,000 psi compared with a max of 60,000 psi and finally a ballistic efficiency of only 18% when one should be looking for a % nearer 30%. Mind you quickload is only a guide but even so this recipe appears to be on the very low side.

    Perhaps some one else with quickload will verify this.

    And... whilst writing I would wish to steer you away (as a new reloader) from the suggestion of seating your bullets in a factory rifle on the lands - better to seat the bullet at SAAMI and then alter the distance from the lands. A rifle can easily have several sweet spots.
    As it was intended for use with the Lee powder dipper I can see that it is likely to be under loaded as to allow for variations in the scoops use. Seating the bullet at SAAMI ? Does that mean seating it the same depth as the maximum stated in my reloading manual ? The max stated was 2.710", I have seated at 2.699", should this be ok ?

    PS what is this quick load you mention ? Sounds like its worth looking into!

    Thanks for everyone's help

    Lloyd

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