Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: 338 Lap Mag neck tension and neck wall thickness advice

  1. #1

    338 Lap Mag neck tension and neck wall thickness advice

    ' been a while since I logged on but I'm looking for guidance on recommended neck wall thickness for neck turning and neck tensions for Sierra 2650C Match HPBT 250 gr heads in Lapua brass being fired from a Savage 110 BA. Any suggestions or "no, no's"? Thanks in advance.

  2. #2
    Is this new Lapau brass ? New brass I would measure the neck of a loaded round and then check out a bush which is 2 thou smaller than this diameter for the neck tension ,

  3. #3
    Yes, new to me, but now fired a few times. Thanks, Outback.
    I now just need to know ideal neck wall thickness for neck turning purposes of this or any new Lapua brass I now purchase. Cheers,

  4. #4
    Quote Originally Posted by AI perfector View Post
    Yes, new to me, but now fired a few times. Thanks, Outback.
    I now just need to know ideal neck wall thickness for neck turning purposes of this or any new Lapua brass I now purchase. Cheers,
    If the brass fits in your chamber then the "correct" thickness should be "just enough to clean it up" with regards to any variations in wall thickness. You'll need to measure the wall thickness (Tubing micrometer) and see how much variation there is.~Muir

  5. #5
    doesn't the bullet act as a mandrel when you seat it leaving neck tension dependant on the brass elasticity?
    (from Lee Vol.2.....)
    I would guess the only anomoly there is the neck thickness that would allow for more tension with a given internal bore

  6. #6
    Thanks, Muir. That's consistent with my own thoughts and would minimize work hardening. So case neck thickness becomes the product as opposed to the objective and my sizing bushing size would be determined by that.
    Yes, Bewsher, though being unable to measure brass elasticity I'll just have to work on how many thou' my neck sizing bushing is less than head diameter plus 2 x neck wall thickness. So the question becomes, just how tight do I want to grip the head. I'm guessing 2 or 3 thou' beyond which elasticity variation between cases may result in grip variances.
    Ant thoughts?

  7. #7
    Quote Originally Posted by AI perfector View Post
    Yes, new to me, but now fired a few times. Thanks, Outback...
    Have you thought about getting the brass annealed? Regards JCS

  8. #8
    Quote Originally Posted by AI perfector View Post
    I'm guessing 2 or 3 thou' beyond which elasticity variation between cases may result in grip variances.
    Ant thoughts?
    I forget the figure but the Lee book referred to a size that necks were "sized" to by the bullet being seated (regardless of what size your bushing is). It was something like 0.001" smaller than the bullet although someone with Vol 2 will be able to confirm
    So if you pull the bullet after seating the bore of teh case neck should be constant assuming the bullets are all constant diameter.

  9. #9
    Yes, JCS, but that's whole new mine field. I'd like to perfect annealing on lesser calibres first and am now getting the necessary kit.

    Bewsher, the implication being that the head is compressed . I'll try and source Lee Vol. 2 and check it through. There's obviously something there that you recall and to read up on - but was it generic or specific to 338. If the former, I am reasonably familiar with turning and tensions for lesser calibres but am looking for any data specific to 338 LapMag.

  10. #10
    no it was not calibre specific.
    It doesnt imply the bullet is compressed.
    in fact the opposite, it implies the bullet acts as a die and "opens" up the neck to accomodate the bullet and the resultant tension is a consequence not of case neck bore size from resizing but from the qualities and dimensions of the brass (i.e. thicker necks with identical bores to thinner necks will produce higher tension figures due to the inherent increase in material to be stretched around the bullet)

    does internal neck surface condition figure in the neck tension issues?

Similar Threads

  1. 243 privvi brass neck neck tension anomoly
    By bewsher500 in forum Ammunition, Reloading & Ballistics
    Replies: 11
    Last Post: 02-02-2013, 16:18
  2. hunting bullet neck tension
    By gr1ffer in forum Ammunition, Reloading & Ballistics
    Replies: 45
    Last Post: 11-06-2011, 16:42
  3. 25-06 loss of neck tension phenomenon
    By Offroad Gary in forum Ammunition, Reloading & Ballistics
    Replies: 18
    Last Post: 04-04-2011, 19:04
  4. Neck Tension
    By willie_gunn in forum Ammunition, Reloading & Ballistics
    Replies: 9
    Last Post: 09-04-2010, 14:29
  5. Barnes X neck tension
    By matt458 in forum Ammunition, Reloading & Ballistics
    Replies: 2
    Last Post: 09-04-2010, 07:46

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •