Chamber depth for cartridge

Discussion in 'Gunsmithing' started by muleyman, Aug 16, 2008.

  1. muleyman

    muleyman Well-Known Member

    Apr 23, 2008
    I was thinking of building a 6.5 Rem Mag off of a Rem 700 338 Win Mag action. I am trying to get the best bang for the buck as far as the price of the build so I chose this round as it has the same bolt face of the Rem Mag but basically duplicates the 6.5-284 in performance. My question is when I tell the gunsmith what I'm building and since its a short action round going into a long action, would he know about the chamber depth to get the long skinny bullet seated out as far as possible. The reason I ask is that looking at the 6.5-284 it is nearly the same case length as the Rem Mag but has an overall length of something like 3.310 where the 6.5 has one of 2.8 something. Is this a possible build or is the 6.5 Rem better off built on the short action.
  2. NesikaChad

    NesikaChad Well-Known Member

    Jan 28, 2007
    Chamber depth has nothing to do with where a bullet is seated buddy.

    Maybe I'm misunderstanding the vocabulary choice your using.

    Chamber depth, in my mind, implies "headspace" The distance from the datum line on the shoulder of the cartridge to the back of the case head. This is never going to change no matter what bullet you use or how long or short its seated.

    Seating depth on bullets has to do with throat length and the physical size of the projectile itself. A long skinny 105 grain "lawn dart" type 6mm bullet is going to require a significantly longer throat than a 60 grain flat base bench rest type bullet. (If you want to realize the potential of the cartridge it will.)

    "Cartridge Length" may be the better choice as this encompasses the whole thing. A guy still needs to be a little careful though because VLD type bullets have a much more "aggressive" looking ogive than say a 107 Sierra MK. That'll require the throat length to be slightly different.
    I would strongly encourage you to load up one or two sample cases with the bullet seated to the depth you want to run. Send these to either a reamer maker (David Kiff, owner of Pacific Tool and Gauge is excellent) or your gunsmith and have the tool built off the sample. It's a very common thing to have done.

    The alternative being the barrel is chambered and then chased with a throating reamer afterward.

    Heavier bullets are going to require being spun harder in order to stabilize also. Generally anything heavy in 6mm and 6.5mm requires a 1-8ROT on the barrel. Best bet is to consult with the barrel maker while placing the order.

    Hope this helped.

    Last edited: Aug 17, 2008

  3. JayIdaho

    JayIdaho Well-Known Member

    Apr 12, 2004
    You would probably be happiest with a custom reamer, owned by you. You can discuss the freebore you want for the 6.5 bullets you are going to shoot, with the reamer grinder and the gunsmith. You can't expect the gunsmith to purchase a special reamer just for your chamber.
    Personally, I think you would be much better off building a 6.5-284. Very good brass now available and a proven longrange accurate cartridge. I'd swap bolts or rifles and leave the 338 as is or build a big boomer on it. Or build a 300 WSM on it, Norma brass is available for the WSM.
    The 1:9 twist barrels are working very good with the heavier 6.5 bullets at around 2900-3100 fps.
    Opinons vary.