338 Edge and bullet jump

Discussion in 'Reloading' started by msalm, Apr 28, 2008.

  1. msalm

    msalm Well-Known Member

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    Jul 18, 2007
    I recently finished my 338 Edge and throated it longer for the 300gr Sierra's as the action is a single shot Nesika. Right now I'm just shy of the lands and the start of the bearing surface is just below the neck/shoulder junction of the case. Just wondering where some of you gravitate to in some of the higher capacity cartridges when loading for them. What kind of jump to the lands do you like to see.... I'm just off the lands about .010 now, and I'm wondering if it should be closer to .040-.050. Accuracy was not bad, but I'm expecting better. Barrel is a 30" Rock 1-9.4" twist with a muzzlebrake I made myself. So far 5 shot groups are 4" at 600 yards, but in all honesty I was not the steadiest when shooting. Laying prone with the bipod I didn't have a rear bag and was limited to about a 2" hold, or at least that's about what I saw in the scope.

    Will seating deeper on these big boys reduce pressure somewhat? Decrease SD? I'm curious.

    Thanks,
    Matt
     
  2. linksmechanic

    linksmechanic Well-Known Member

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    Jan 16, 2007
    IMO I would go to .020 but thats about it. Those are excellent groups for that range. I wouldn't seat the 300's to the lands. I think they would spike pressure. I seat bergers to the lands but they are a different animal.
     

  3. Lightvarmint

    Lightvarmint Guest

    First, let the rifle tell you where it wants the bullet seated by doing some diagnostic testing. I would expect that you will come in between .020" and .050" distance of the ogive to the lands when shooting high performance loads. For example, the 338/378 I use likes the SMK bullets (BC .768) at .030" off the rifling at 3011 fps.

    With the 280 grain Aluminum tipped bullets (BC .878) from Gerogia, the same gun likes those at .050" off the rifling at 3130 fps using the same powder lot as above.

    James
     
  4. msalm

    msalm Well-Known Member

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    Jul 18, 2007
    Thanks for the input guys. With H1000 and 300gr Sierra's I started a bit too high of charge and a little too close to the lands for what I was doing. Like a D*mb *ss I didn't have my load reference data handy and I was in a hurry to load em up and shoot em. Loads were at 2900+- FPS. I loaded up the last batch at a more sedate 92grs and I think I'll start with the bullets .030 off the lands and work up the charge to where the SD is good, then play with seating depth and see what the gun wants to shoot.

    Here's the rundown of the setup I put together.
    Nesika V single shot action
    McM HTG stock with adj comb
    30" Rock bbl 1-9.4 twist (.950ish at the muzzle)
    Home made brake
    Leupold MKIV 6.5-20 with TMR reticle

    Initially I just wanted something that would take me to 700 yards, but now I'm thinking this will be capable of that and a bit more!
     
  5. Lightvarmint

    Lightvarmint Guest

    Hello,

    I would take the loading you have described and either start it a .010 off the lands and work out to say .050 off the lands or do it in reverse. I usually start closer and work out as the pressure lessens as the seating depth is farther from the lands. However, either way should work.

    James
     
  6. RDM416

    RDM416 Well-Known Member

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    Jan 31, 2005
    MSALM,

    I am shooting a 338 Kahn (338/378 Wby wildcat) with a Nesika action and Lilja barrel. With both the 250 and 300 SMKs I have found that I need to seat at least .010 to avoid a significant pressure spike. I am now seating 250s out to .025 for my standard load. This gives me the highest velocities without pressure problems and does not seem to have a noticeable effect on groups from seating at .010.