30/06 Case Cap Trial

Discussion in 'Reloading Forum (All Calibers)' started by Pawnee Bill, Mar 24, 2019.

  1. Pawnee Bill

    Pawnee Bill

    Joined:
    Jan 8, 2012
    Messages:
    252
    I just finished checking the capacity of my '06 brass just out of curiosity. I checked 5 LC69 cases against 5 Lapua cases. The Lapua cases averaged 69.4 gr and the LC69 was 67.6 gr for a whopping 1.8 gr difference. Does that sound about right? I was kind of surprised at so little difference.

    I used distilled water and the LC69 cases were pull downs, never fired. The Lapua cases were 4x fired. After firing the GI cases I will check them again.
     
  2. Uncle Ed

    Uncle Ed

    Joined:
    Aug 1, 2018
    Messages:
    566
    When you measure case capacity according to Quickload it should be done with cases fired in "your" chamber.

    That being said the larger the case and its capacity the less it will effect pressure and velocity. Meaning a smaller case like a .22 Hornet or .223 will be effected more by variations in capacity.

    Example using the chart below and Quickload there was a 5,000 psi difference in chamber pressure with the same 25.0 grains of H335 between the top Lake City case at 30.6 and the bottom Lapua case at 28.0 case capacity.

    [​IMG]
     
  3. Wildcat455

    Wildcat455

    Joined:
    Feb 27, 2018
    Messages:
    42
    1.8 gr of case volume is pretty significant in my world, but your data will mean more to you after the cases are fire formed in your rifle.

    For the shooting I like to do, (which is long range target and hunting) when it comes to developing loads for 30-06 and larger cases, I like to keep the volume range to .5 gr or less. I find this is easier to accomplish by keeping my case weights in same lot brass to 1 gr total per load workup. For example 30-06 case weight (with primers) 192.0-192.9.

    OP, In your example of volume difference, those cases would have about a 45 fps spread and about 4,600 psi chamber pressure difference when loaded exactly the same. (Depending on powder choice of course.)

    Holding the case volume to .5 gr total difference will give a variance of velocity of about 10 fps and pressure variance of about 1000 psi when otherwise loaded exactly the same (Again, depending on powder choice.)

    At 1000 yards, a velocity difference of about 6 fps is about 1" of vertical. At 100 yards, you wouldn't even notice it.

    For my type of shooting, I would notice a 45 fps and 4,600 psi difference.

    Really, it's up to you to decide if any of this is meaningful or worthwhile to the type of shooting you do.
     

Share This Page