Is this excessive pressure???

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by PrimeTime, Feb 5, 2002.

  1. PrimeTime

    PrimeTime Well-Known Member

    Messages:
    256
    Joined:
    May 9, 2001
    Just started developing loads for a 6.5-06.
    I am reaching fairly hot loads and have only one possible hint of excessive pressure. The brass is new Winchester 25-06 and when unfired, measures .464 at the base. After the first firing, they measure .468 at the base. There is NO cratering of the primer dimple, primer edges are totally rounded just as they went in, and the bolt handle lifts easily with 2 fingers.
    I assume that this expansion at the head may be just from the brass being new. What do you guys think?
     
  2. Dave King

    Dave King Well-Known Member

    Messages:
    2,362
    Joined:
    May 3, 2001
    What's the expansion (case head size) with a "non-hot" load?
     

  3. PrimeTime

    PrimeTime Well-Known Member

    Messages:
    256
    Joined:
    May 9, 2001
    All the cases measured .468 after the initial firing. Again, there are NO visible signs of pressure. I am just wondering if it is possible to get excessive pressure without it showing in the primers and without the bolt opening hard.
    Any suggestions would be appreciated.
     
  4. grkldoc

    grkldoc Member

    Messages:
    9
    Joined:
    Feb 5, 2002
    I suppose it depends on you definition of excessive pressures. I have had loads with normal appearing primers, no ejection marks, no or slight sticking which have had pressures in the 70-75K range based on monitoring with a peak strain meter. Yes, it is possible to have excessive pressures and not recognize it with traditional signs. Personally, I believe that if you have signs as above you are already way over acceptable pressure. This is why I have gone to load developement with a chronograph and a peak strain meter. Once I started using the peak strain meter it completely redefined my maximum loads. Measured data is much more useful than guessing.
     
  5. PrimeTime

    PrimeTime Well-Known Member

    Messages:
    256
    Joined:
    May 9, 2001
    Yes, a guage to measure the actual pressures would be ideal. Unfortunately, no such device is at my disposal. I always develop loads using a chronograph and am nearing max with this particular load but it's certainly nothing especially fast. Again, it's a 6.5-06 and the velocity with this load averages 2,920 fps but I have shot one grain hotter for 2,975. Both loads show none of the typical pressure signs at all. I am convinced that it is just my case filling out to the chamber. I am definitely not going any hotter though.
    Thanks for your responses.
     
  6. Brent

    Brent Well-Known Member

    Messages:
    2,537
    Joined:
    Jun 12, 2001
    Are you measuring across the web or the casehead itself?

    The belt on my 416wby will start at .602" and go to .605" with virgin brass. They will go to .606-7" if the loads are near max. If loads are kept at what caused expansion to go to .605", it never gets larger.

    With what causes them to go to .607", the next load will go .608" and so on, until they are hard to extract at what seems to be a couple more reloads. After I check this on the Oehler 43 I'll know what PSI is doing what.