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Thread: Bullet seating depth?

  1. #1

    Bullet seating depth?

    A friend of mine came over to load his first .270 bullets using my press etc. And after looking at his combination of powder/bullet choice etc.(100 gr speer hp) i looked into the c.o.l for this load which was 3.225 (minimum i think from memory), With this bullet you could seat it to an absouloute minimum and they wouldf still cycle in the chamber and magazine etc. But the question i have is what would be a minimum safe depth to seat the bullet to..????


  2. #2


    There is an awful lot of crap surrounding bullet seating depth, specifically distance to rifling etc. Unless you are into specialised target shooting it really is not worth the bother as it is just one factor in many that may alter the performance. A good guide which has always given me excellent results is to seat the bullet to calibre depth.

  3. #3

  4. #4
    There are good reasons not to seat bullets out too far. One is tht if you load to specified OAL for that bullet, you will be assured (generally) that the rounds will fit and cycle through the magazine. Another good reason to keep a goodly bit of the bullet inside the case neck is that the amount of the grip the neck has on the bullet dictates "pull weight", or the amount of effort needed to break the bullet free of the neck. This friction on the bullet by the neck helps make the pressures uniform.

    I used to believe that bullets seated to the lands shot the best but I'm not convinced anymore. Now I use magazine length and go shorter from there.~Muir

  5. #5
    Muir Thanks....

    Yes this is obviously a small bullet head for the .270 and you could stick it on with superglue and it still wont touch the riflings and cycle thro the magazine...

  6. #6
    In the meantime I'm also a believer of the seat to diameter theorie.
    With boat tails the bearing length to about the same as the diameter.
    Also stay at or under SAAMI length, my mag wouldn't allow more anyway.

  7. #7
    I confess to being more anal than that

    If I have a new rifle/new barrel - I make up 4 batches of 5 rounds; the first set 5thou off the lands, the next 10thou, then 15 thou and then 20thou. I then see which shoots best. (I tend to use a reccommend load from other shooters who have the same calibre, provided it not close the max reccommended).

    I then tune the next set of loads up and down by 2thou from the best shot group of the above.

    In general I have found that the best results come from between 3 and 7 thou off of the lands for normal rounds and touching the lands for VLD's.

    Once I have the depth I then tinker with the powder loads, neck tension etc and if necessary start the seating tests again...!

    All this said, once I have the load I want it never changes until the rifle or barrel get replaced.

    I told you I was anal



  8. #8
    Most of my rifles are Tikka and the rifling starts well done the barrel. I could not load the bullets out enough and fit in the magazine. Obviously Tikka must have a good reason for this and they are known to be accurate rifles.
    I buy some factory ammunition with the bullet type and weight I am interested in. Tikka seem to like Federal and Hornady. I chronograph these and reuse the cases. I load the bullets to the same length as the factory ones and slowly work up the load to try to get the bullets going the same speed while checking for signs of overpressure.
    When this is done I shoot for group and assess the results. If I get a good group I leave well alone. With this baseline I can always experiment with different powders, loads primers etc. I never change more than one variable at a time and I have found that different seating depths can change the MV and pressure.

  9. #9
    Wow. What effort you go to! Impressive.

    Just confirms to me that I'll stick to buying factoy loads. Reloading seems a dark art!


  10. #10
    Re-loading is not a dark art , it is mainly commonsense .
    Some people DO make it hard work though !


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