How much neck tension?

FORESTBARBER

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Following Redding's re neck die bushing suggestion results in significantly less neck tension - as gauged by seating effort - for once used Lapua .308 brass vs new Lapua brass.

Velocity is about 80 fps quicker with the reloads, though I used Win primers this time vs Rem primers.

All other things being equal, 175 SMK, 44gr Varget, Lapua brass accuracy seems great.
 

Rob01

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Re: How much neck tension?

I use .002" of neck tension on my .308 loads.
 

MitchAlsup

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Re: How much neck tension?

The amount of nect tension is application dependent. It can be as little as 0.000 for benchrest ammo, although more typically 0.0005 (yes 3 zeros and a 5). It can be as great as 0.003 for harsh semi-auto actions.

For ammo that needs to remain accurate and still be able to suffer a little abuse between the reloading station and the final firing position, something on the order of 0.002 is recommended.

There is no reason for more than about 0.003 as the case neck will simply yield as the bullet get seated. So, if you need more than 0.003, you should look into crimping.
 

FORESTBARBER

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Re: How much neck tension?

Thanks. I am running this ammo in a M40 bolt gun. Using Redding's recommendation of a neck die 0.001" smaller than diameter of o.d. of neck of a loaded round.

I appreciate the info.

Forest
 

Greg Langelius *

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Re: How much neck tension?

I use the minimum neck tension necessary to successfully resist attempts to turn the projectile in the case neck using thumb and forefinger.

I achieve this with a F/L resizing die by backing the die off so it only resizes the end portion of the neck, and testing as I rotate it back down. When I reach the depth where the bullet won't turn, I'm there.

The unsized portion of the neck is nearly the same diameter as the chamber neck, and helps center the front end of the round when chambering. The very bottom of the case remains fully expanded, and helps center the base portion of the round on chambering. The net effect of all this is better case concentricity within the chamber; and donuts, even if present, appear to be a non-issue.

Periodically the case need to be bumped, and for .260's I suggest the use of a .308 die, for .308's a .358 win, etc.

Greg
 

milanuk

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    Re: How much neck tension?

    Depends on what brand of brass.

    For Lapua brass that has been neck-turned to 0.014" and finishes with a loaded neck diameter of 0.336, I use a .334 bushing... but I also use a floating carbide expander button that just 'kisses' the inside of the neck to ensure it is .306 where it counts.

    YMMV,

    Monte
     

    FORESTBARBER

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    Re: How much neck tension?

    I am, more or less, accidentally doing a la' Greg's method. Using .336 bushing with Lapua fire formed brass a little more than a third of neck length. Bullet can just about be seated by hand.

    Seemed pretty loose versus virgin brass. But glad it is fairly close to expert's practice.

    Forest
     

    427Cobra

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    Re: How much neck tension?

    .002 works, I do as Monte, Reddings carbide floater ball kissing the inside, runout is always low
     

    Greg Langelius *

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    Re: How much neck tension?

    I feel mildly uncomfortable wearing the title 'expert'; I did not originate the method. It had been around long before I took uphandloading. I got it from my Elder Brother Bill now nearly 20 years ago, who had been hanging out with the original 1950's/1960's BR folks, and way back when, most of them were making do with plain old plain old dies.

    Greg
     

    FORESTBARBER

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    Re: How much neck tension?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">I feel mildly uncomfortable wearing the title 'expert'; I did not originate the method. It had been around long before I took uphandloading. I got it from my Elder Brother Bill now nearly 20 years ago, who had been hanging out with the original 1950's/1960's BR folks, and way back when, most of them were making do with plain old plain old dies.

    Greg </div></div>

    Maybe I should have said "people with 20K+ posts on this forum" Feel better?
    smile.gif


    Best Regards,

    Forest
     

    The Mechanic

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    Re: How much neck tension?

    It is all about consistancy of tension not just amount of "squish".
    in the article secrets of the Houston wherehouse
    http://www.angelfire.com/ma3/max357/houston.html
    consistancy of the tension was said to be the single most important thing to accurate reloading. Lots of factors as mentioned above will change the actual tension
    Annealing
    how many times brass has been resized
    manufacturer of brass
    bullet composition
    sealant on inside of neck
    lube on inside of neck
    galvanic corrosion between brass and bullet.
    etc.
     

    Greg Langelius *

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    Re: How much neck tension?

    Best regards back atcha. I agree that neck tension is very important, and may indeed be most important.

    The problem with bushing dies, etc., is that they are a fixed solution to hitting a moving target. Every time the brass gets worked, it gets hardened, and using the same tools consistently will render equally inconsistent results.

    I use my 'find the right adjustment' method each reloading cycle, and while the measurement means may be unscientific, they are somewhat more realistic than choosing a bushing diameter and going with it blindly and unalterably. FYI, as the brass hardens, the resizing dies should move <span style="font-style: italic">up</span> and resize a shorter portion of the neck. This is because the resizer ball encounters more resistance and generates less springback as the brass goes harder.

    While many resist employing the resizer ball, they still encounter similar problems due to work hardening. For me, the resizer ball is another subjective means of judging brass hardening.

    If the bias on the adjustment is toward the lesser neck tension end, finishing each reloading cycle with a twist can find and cull the ones that are on the 'not enough' end of the neck tension scale.

    Greg