Factory ammo in custom chambers

Discussion in 'General Discussion' started by J E Custom, Oct 7, 2011.

  1. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    Over the years I have seen factory ammo that was loaded to hot for "Custom" chambers and
    have experienced this again with the new Superformance ammo.

    Note;This is not a criticism of the ammo just a warning if it is used in anything but a SAMMI

    With out a doubt, it does prodeuce more velocity. But in all of the SAMMI chambered rifles it
    was tested in it is "MAX" Pressure and the signs were present (Heavy bolt lift,ejector marks on
    the case head and flat primers.

    I have not tested it in a factory chambered rifle so any input would be appreciated to put
    everything into perspective.

    Most on this site load there own ammo and start low and work up, But some use factory ammo
    to form a basis for accuracy and velocity, and use it to do break in on new barrels. My concern
    is that someone will use the HOT factory ammo on there short throat ed,Tight necked minimum
    free bore chambered rifle and have problems.

    This is not the first ammo that has not been suitable for custom chambers, My first experance with
    this probablem was the big Weatherby cartriges that were loaded to the Max for there factory rifles
    with tons of free bore. If this ammo was fired in a custom chamber with tighter dimensions and
    little or no free bore it would blow the primers and cause heavy bolt lift.

    So if you have a custom chamber and want to get more velocity some factory loaded ammo may
    cause problems and could even be dangerous.

    As stated earlier, This ammo has performed well and with the longer peak pressure curve has
    all the things we want in order to achieve max velocity, but there is no free ride and make no
    mistake about it these are MAXIMUM pressures and come with the problems associated with
    Maximum loads.

    MY recommendations for what it's worth, is not to shoot any of the high pressure ammo in a custom
    chamber unless it is SAMMI spec.

    Comments are more than welcome. It may keep someone from having a problem or even getting

    Just a heads up

  2. ken snyder

    ken snyder Well-Known Member

    Jul 26, 2010
    I will mirror JE customs concern about factory ammunition in custom chambers. The 338-378 is a prime example. The original person who had the rifle built is always repeatedly informed that his short throat is no longer a 338-378 Weatherby. The thing that chokes my goat is the amount of custom chamberings that the barrels are engraved as being the original parent cartridge.
  3. shortgrass

    shortgrass Well-Known Member

    Mar 31, 2010
    Chambers that are not SAAMI need to have the dimentions that are altered on the barrel, engraved or , at least, stamped.
  4. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004


    I have encountered rifles that had been altered even to the point of rechambering to a larger
    case/cartrige that had not been changed.

    It is the obligation and responsibility of everyone that alters a chamber to give a good description
    of the cartrige and special dimensions.

    Also I have an update on more of the Superformance ammo. It appears that when fired in an AI
    chamber that it is not as hot as a standard chamber. (When SAMMI loaded ammo is used while
    fireforming) The extra chamber space allows the case to expand lowering the pressure.

    Both chambers had the same free bore and neck size but one had been Improved.

    Anyone else that uses this ammo please look at the brass and add your comments.