S1, more seating depth questions

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by rufous, Jun 16, 2003.

  1. rufous

    rufous Well-Known Member

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    S1, I have some more questions for you regarding seating depth. This is most interesting stuff. You mention a 30 degree angle from neck to throat (freebore). Is 30 degrees standard or are chambers cut with a wide range of transitional angles? Also you prefer a 1 degree leade. Is there that much difference between a 1 degree and the more standard 1.5 degree leade? What difference would there be between the two leade angles? Am I envisioning it correctly that a 1 degree leade would be a gentler transition to the lands than a 1.5 degree leade? You said that the number of grooves the barrel has will affect the amount the bullet should engage the lands. Do you have a normal amount into the lands for a 3 groove and 4 groove and 6 groove? Let us assume we have a 300 Winchester Magnum with a 1.5 degree leade and a parallel throat that is 0.3083” in diameter on a 4 groove and on a 6 groove barrel. How much into the lands would you likely see these setups shooting at their best? What kind of range in seating depths do you experience with the various parameters? Are we talking that you have found all your rifles shooting best at just touching the lands to as much as 0.015” into the lands or is the range more than that? When I say just touching the lands I should specify that I determine that depth by use of the Stoney Point tool.
    How far can one seat the bullet into the lands without the lands seating the bullet into the case? I suppose that would depend on neck tension. I do not understand what you mean by 0.0012” press fit of neck tension. Does that mean that the inside diameter of the neck is 0.3068” after resizing and before seating the bullet? I am using standard dies, not the Redding bushing dies so I can only decrease neck tension by turning necks (I am not confident that I could grind the expander ball accurately in order to reduce neck tension). Again my major application is for a big game rifle so I need more neck tension than a benchrest shooter would and of course my accuracy needs are no where near as great.
    Finally I am still wondering if this all applies to match bullets only or do you find that the big game bullets (Nosler Partition, Barnes X etc) also shoot best when seated into the lands?
    Thanks again for offering your experience to the rest of us, Rufous
     
  2. Guest

    Guest Guest

    45 degrees is standard for most reamer makers.

    1 degree throat is better because it gives more of a range in seating depth options while still being able to extract a loaded round without leaving the bullet in the barrel.

    I would pitch the Stoney point tool, spin the bullets in fine steel wool, and seat the bullets based on the neck tension I was using and the results on the target.

    .020" into the lands is a good place to start.

    .3083 is a little too tight, I would prefer .3086" for freebore.

    Get rid of the expander ball. JUST DO IT.

    Please save yourself a lot of hassle and invest in a full length neck bushing die.

    All bullets shoot better when seated into the lands properly.

    Consistent neck tension is very important, turn necks so that the outside diameter of the neck is .0012" larger after the bullet is pressed in place than before it was pressed in place. This means you will have to have the right sized bushing.

    Good Luck [​IMG]
     

  3. rufous

    rufous Well-Known Member

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    S1, thanks so much. I will try what you suggest, at least as far as I can at present. I am limited by the chambers I have, but I can get the resizing die you suggest and work to have the 0.0012" press fit neck tension. To achieve the 0.0012" neck tension you say I would need to turn the case necks. Would it not be possible to leave necks unturned and just buy a larger diameter sizing bushing so long as the necks were within 0.001" thickness? Or is that not precise enough? I guess it all depends on what I am looking for and what is precise enough for me but could I basically achieve the same results that way? Again I am using a 8.5# 300 Win Mag with a skinny sporter stock and 0.5" 3 shot groups at 100 yards would be entirely adequate. Rufous.
     
  4. Guest

    Guest Guest

    Depends on a few things....

    1) The weight of the bullet

    2) The weight of the gun

    3) Bullet coating

    4) Muzzle brake?

    5) The annealed state of the neck
     
  5. rufous

    rufous Well-Known Member

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    S1, another question I have is if 0.0012" neck tension would be enough to keep the bullets in the magazine from seating deeper into the necks from recoil? Rufous.
     
  6. rufous

    rufous Well-Known Member

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    S1, bullet weight would be 200 grains. No coating. Holland quick discharge muzzle brake. 8.5# rifle. Federal brass with necks as from factory. Most importantly how necessary are these techniques to achieve consistent 3 shot groups in the 0.5 to 0.75" range at 100 yards? Rufous.
     
  7. Guest

    Guest Guest

    Many guns will shoot inside 3/4 MOA with a .003" press fit and the bullet not in the lands, if 100 yards is the measure. Try not to get baited into thinking that 3/4 MOA will hold up at longer range if you do not have control of neck tension and velocity extreme spread.
     
  8. moosehunter

    moosehunter Well-Known Member

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    Question for S1. You say get rid of the expander ball. That sounds interesting. Why would you reccomend this. Would greatly increasing neck tension increase accuracy?
     
  9. Guest

    Guest Guest

    I think excessive neck tension is counterproductive to accuracy. I should have been more specific. What I really meant to say is, "Use a full length sizing die that incorporates a changeable neck bushing in its design, thereby removing the need for an expander ball and giving better control over neck tension, and more concentric ammo."

    If one of the goals is to load concentric ammunition, neck wall thickness must be very consistent, requiring turning necks with most lots of brass. Long range shooting also demands controlling vertical stringing, which in turn demands controlling neck tension. Turning necks will help these issues:

    1) Standard Deviation of Velocity

    2) Concentricity of ammo

    3) Accuracy (vertical stringing)
     
  10. moosehunter

    moosehunter Well-Known Member

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    I do turn necks, and anneal. Today I was loading rounds for a 1000yd match in Burns Lake BC and after reading your post I did notice they were quite "loose". Bringing to mind some dates but thats another story. In some ways loose may be good for soft seating but in others mayhaps not. Educate me.
     
  11. Guest

    Guest Guest

    I believe that light neck tension and into the lands is best for ultimate accuracy. Dangerous game, semi-auto rifles, and arctic conditions all require more neck tension and the bullet NOT stuffed hard into the lands.