bullet seating depth for 7mm rem mag

Discussion in 'Reloading' started by DIGGA, Jun 13, 2009.

  1. DIGGA

    DIGGA Member

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    [​IMG] bullet seating depth for 7mm rem mag
    I have some sierra 168gr HPBT Match king projectiles. Nosler brass and AR2213SC powder, Just wondering how deep to seat the projectiles, also the rifle is a Remington Sendero. Any ideas on good primers. If any one could give some advice it would be much appreciated.
     
  2. Rustystud

    Rustystud Well-Known Member

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    I would suggest you measure and establish your chamber throat depth first. Then you will have a reference point to start from. Since you are shooting a Remington you might also see if your mag well is long enought to accomodate bullets seated out far enough to touch the rifling. This is a problem often encountered with Remington rifles. Remember some bullets do better jumping and others do better engaged.

    Nat Lambeth
     

  3. Limbic

    Limbic Well-Known Member

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    I've heard that the 7mm and many other magnums like the bullets .03 and farther off the lands. You just have to try different depths out. Bergers go .08 while Barnes MRX is .03. Jammed to or in the lands just didn't shoot well. Shilen barrel/chamber however.
     
  4. Rustystud

    Rustystud Well-Known Member

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    There is no absolute rule but some say Tangent Ojive bullets tent to like to be jamed and Secant Ojive bullets like to jump.

    The manufactures of Barnes and Swift Sciroccos say they both need a jump to prevent an excessive preseure spike.

    In older days one of the things we tried not to encounter was a bimodel presure curve. Thoughts were that it caused irratic groups.

    It has been my experience that Berger Bullets shot better toughing or into the rifling a few thousands and Sierras liked to jump about .003.

    I am getting ready to to work over a 7mm Magnum for a customer. It is a Remington 700 Sendaro. I have adjusted the trigger down to 1 pound. It is in a HS Precision stock and has an aluminum bedding block. I will glass in the lug to further stabilize the action. The crown will be cleaned up to remove any doubt. I will test with Nosler Balistic Tips because they are cheap and usually are easy to get to group. If I can get it shooting well I will change over to Accubonds or a more serious controlled expansion round. I will start with som conservative loads and work up to a hotter round .5 grains at a time. I would expect to find a accuracy node around 3100 fps.

    Nat Lambeth
     
  5. Limbic

    Limbic Well-Known Member

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    let us know how it turns out. I tried the Bergers just like the sticky on here suggested. With near max powder the group was significantly better at 80 thou off the lands.

    I guess it also matters on your over all chamber depth as to your COAL.

    Also with a deeper seating you decrease the volume of the brass. Full brass shoots better than One that is only partially full.
     
  6. Rustystud

    Rustystud Well-Known Member

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    Generally you will find seating depth of VLDs and boattails below the neck shoulder juncture to be detrimental to accuracy. remingtons are known to have deep throats allowing seating depths that will far exceed magazine length. They make their throats long because of long bullets and presure issues. It really screws the guy who wants to shoot shorter bullets.
    Nat lambeth
     
  7. shootinfool

    shootinfool Well-Known Member

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    Just as a general rule, once you have established your max seating depth to where the bullets touch the lands and grooves I then back off about .005 and then go in .005 to .010 incriments to find optimal seating depth. Just a reminder check to see what the max length you can have a bullet while it still fits into the magazine, that is if you intend to use the magazine.
     
  8. Rustystud

    Rustystud Well-Known Member

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    Over the last couple of years I have had several Remington 700s and model 7s with tthroat lengths way beyond SAAMI and CIP specs. Especially on 308, 5R mil spec rifles. Having discussed this with numerous other gunsmiths and the Reamer maker(s) that Remington uses we have come to a consensus that the folks at Remington are running wild with throating reamers or flex hones. Because of the barrel contours (lack of metal) the factory barrels can not be saved and have to be replaced. Properly cut chambers will allow for bullet seating that will work using the magazine. I have saved a few factory barrels by using Kevin Wyatts extended mag boxes (+.110 longer) and some machining of the loading ramp.

    Nat lambeth
     
  9. Clark

    Clark Well-Known Member

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    I have a Ruger #1 in 7mmMag that likes 3.34" with any bullet.
     
  10. DIGGA

    DIGGA Member

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    Thanks for the info about checking the throat chamber depth first Nat.Everything seemed to go like clockwork after that, my overall cartridge length when touching the rifling came to 84.55mm, then I backed it off .254mm giving me 84.3mm. They seem to chamber quite good with plenty of free play in the mag. I have loaded 4 groups of 3’s that I will hopefully be trying out on the weekend :- 63gr. 63.5gr. 64gr. & 64.2gr .
    Once I find my best group with the powder, then I’ll play around with either getting further or closer to the lands
    Thanks very much for your helpful advise Nat.
     
  11. DIGGA

    DIGGA Member

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    I must be pretty close to the ball park because there is only .03"(.076mm) difference between your bulletts & the measurements I have found & loaded up, thankyou very much for the input Cark.