Throat lenght Vs Performance

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Topshot, Nov 17, 2009.


Help Support Long Range Hunting by donating:


  1. Topshot

    Topshot Well-Known Member

    Messages:
    1,085
    Joined:
    Nov 3, 2008
    Any one shoot a rifle with a very long throat?

    With long VLD type bullets seated into a cartridge with a standard chamber, the bullet must be seated well down into the case and this uses up powder capacity.

    If you single load and don't use the magazine, then it would be possible to seat some of the VLD type bullets out quite a distance if the chamber is cut with a long throat.

    This should be similar to having an improved chamber.

    My lattest rifle is chambered this way and I seem to be getting about a 80 fps to 100 fps gain befor I see pressure signs.

    I would be interested to hear from those that have tried this as to what sort of velocity gains they are getting over a standard chamber.
     
  2. fj40mojo

    fj40mojo Well-Known Member

    Messages:
    392
    Joined:
    Jul 25, 2009
    That is great as long as your rifle is a push feeder, but if you've got a Mauser action, Ruger 77 Mk2 or other controlled round feeder that have to feed out of the magazine then the mag length becomes your COAL limiting factor. Common problem with 6.5x55 which is long throated to begin with in SAAMI chambered, you can't seat the bullets out far enough to reach the lands and still feed out of the magazine with controled round feed actions. The Swede I'm having built right now on a '98 Mauser action will be chambered with a 6.5x55 Match reamer from PT&G and hopefully I won't have this problem.
     
    Last edited: Nov 17, 2009
  3. MontanaRifleman

    MontanaRifleman Well-Known Member

    Messages:
    6,194
    Joined:
    May 21, 2008
    My Senderos and Sako all have long throats. The 300 RUM will seat the 210 Berger to the lands with the bearing surface catching most of, but not quite all the neck. I only partial size the neck anyway. The Sako 300 WSM will seat the 210 Berger to the lands and only catch about 2/3rds of the neck. Hard to say what velocity gains I'm getting because of the throat, but I suspect a little. since the bullet is taking less case space, that's more capacity for powder.

    Mark
     
  4. Topshot

    Topshot Well-Known Member

    Messages:
    1,085
    Joined:
    Nov 3, 2008
    fj40mojo,
    Good point on the controlled round type actions. My action is a Rem 700 so I don't have to deal with that issue.
    How do you think a 6.5x55 would go in a Rem 700 action? You could seat those long bullets way out and use more case capacity.
     
  5. fj40mojo

    fj40mojo Well-Known Member

    Messages:
    392
    Joined:
    Jul 25, 2009
    I think the Swede is a severely under rated cartridge. Most all the factory ammo is castrated because of all the Krags and other weak actions that are still hanging around the exception being some of the European mfg ammo. Most of the loading data for the cartridge is geared for these old rifles too, so if you are looking to these sources it appears to not be much of a cartridge, but nothing could be farther from the truth. In a modern action with good metallurgy the Swede sits somewhere in between the .260 and the 6.5x284 but you have to work up your own loads. If you've got a true long action the issue of the long throated SAAMI chamber is moot cuz you can do just exactly what you're doing, seat those long bullets waaay out there, use the case capacity gained to squeeze just a little more velocity out of it without burning your barrel up in 1K rounds, and you'll probably still be able to feed from the magazine. I'm going with the Match reamer cuz of my slightly shorter '98 Mauser action.