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Seating depth Determination

Discussion in 'Handloading and Reloading' started by hankpac, Apr 11, 2007.

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  1. hankpac

    hankpac Member

    Jan 7, 2007
    I am loading a new batch of 22/250, in a custom chamber (Rem 40X) and barrel (SGY).
    I want to determine seating depth to just touch the lands or just about 2000s off. The manual length seems a little deep. The bullet is almost up to the ogive.
    How do I determine this accurately, rather than hit and miss or guess.
    I was once shown a method that used a cleaning rod, and marking it with a pencil, but I don't know how we did this.
    I will exclusively neck size, once the cases have formed to the chamber, and use them only in this rifle. I'll be using 34 gr 4895, and 50 gr vmax.
    Thanks for your help.
  2. ReloaderFred

    ReloaderFred Member

    Apr 28, 2005
    Oregon Coast
    The cleaning rod method ( I have a tool made by a local machinist many years ago that does it better) is simply using a solid rod and with the bolt closed (unloaded rifle, of course), lower the rod from the muzzle until it rests on the bolt face. Mark the spot on the rod exactly even with the muzzle. You have to use a solid rod so the bullet won't go into the female portion of the cleaning rod. You want to measure from the tip of the bullet.

    Withdraw the rod and with the bullet you're going to use, place it in the throat of the chamber until it rests against the leade as far as it will go without being forced. Hold the bullet in place with a pencil or wooden rod, and then lower the solid rod into the barrel from the muzzle once again, until it just rests against the tip of the bullet. Mark the spot on the rod exactly even with the muzzle. Now measure the distance between the two lines and this will tell you the maximum distance to the tip of the bullet, from the bolt face. The caveat is that bullets vary in length, but this will get you close.

    Once you have this measurement, then deduct the amount you want to back off from the rifling and you'll have the over all length to start with for this particular bullet. I like to start .020" off the rifling to start, but this is something you have to decide for yourself.

    If you change bullets, you'll have to take a new measurement for the new bullet, since the ogive will be different, as well as the length of the bullet.

    Hope this helps.

  3. Bullet

    Bullet Member

    Jan 20, 2003
    While this is not what you asked for you might consider this (copied from another forum) –

    “There are some pretty universal rules about seating a bullet. You first seat the bullet to a given depth and then work up with the charge. To do otherwise might lead to a pressure excursion. Do you know how to read pressure in a rifle case??? If the radius of the primer is gone,the bolt lifts hard,you can see the extrusion of brass back into the elector hole,see the machine marks on the bolt face in the brass or the primer flat falls out of the case the load may be a bit hot. BUT, this can and will happen regardless of where the bullet is seated if you tip the powder bottle too much. Here's a very easy way to develope a load:
    1)-Set the bullet into the lands(if you can reach them) as much as the neck tension of the case will allow.
    2)-Start with a minimum listed powder charge-10% for the bullet weight
    3)-Work the powder charge up till the groups get as small as they will get.
    This depends on the rifle.
    4)-After getting as small a group as the rifle will shoot at the jam,back the bullet off.002/.003 at a time and see if the groups improve.Depending on the rifle they may or may not.
    5)-If you decide on trying another bullet back the powder down and go back to the jam length and start again.
    What this saves is guesswork. If the bullet is seated HARD into the lands then the only way to go with it is shorter. If the bullet is seated HARD into the lands and you have a safe working load pressures will NOT increase as the seating depth is shortened. If you, at any point,. get pressure signs, STOP. Back off the powder and start up again and see if it repeats. Be aware that a load shot at 70 degreesF. may not be a safe load at 100 degrees F.Back a load off when you change ANY part of that load including changing lots of the same brand of powder. Never assume anything;prove it to yourself. There is not really a lot of rocket science in rifles; experience is much more important”
  4. uk roe hunter

    uk roe hunter Member

    Jun 30, 2006

    Hi guys
    I make up am inert dummy round with the bullett seated a long way out then i gently try to chamber it out of the mag (mauser action) you will feel resistance if it is too long, work it back very gradualy until it loads easily the remove it and smoke the bullet using a candle then run it back into the chamber, eject it and have a look if there are rifling marks in the sootmove it back very slightly (half a turn on my seating die). try it again there should be no marks on the bullet.

    If your end product is shorter than the col given in the reloading manual drop the load of powder a grain or so further. It is very unlikely that it will be though. If the bullet has a cannulure it is likely to be well out of the case, don't worry about that. you need at least the diameter of the bullet in length in the neck to give enough tension. more in the case of a boat tail.

    I hope this has been of help

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