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Forming 260 brass from 308 brass

bschneiderheinze

Sergeant
Full Member
Minuteman
  • Nov 30, 2011
    1,402
    308
    46
    Behind the Glass
    I have read that it is fairly simple to form 260 brass from 308,but cant seem to find anywhere that details the process. Is it as simple as taking your 308 brass and running it through a 260 die or more involved. I have never neck turned brass. I am currently thinking about switching my main 308 bolt gun to 260 and have a ton of 308 brass.
     
    Re: Forming 260 brass from 308 brass

    You will have to be careful that the necks don't get too thick, other than that, yes it is as easy as running your brass through a 260 FL size die.
     
    Re: Forming 260 brass from 308 brass

    By all means you can make 260 brass from 308, but how in the hell are you going to make it longer, 260 minimum trim length is 2.025, and most chambers that is too short, my trim length is 2.035, most 308 cases are around 2.005, simple easy way is to put Winchester 7-08 brass in a 260 FL die and rock on.
     
    Re: Forming 260 brass from 308 brass

    <span style="font-style: italic">"Is it as simple as taking your 308 brass and running it through a 260 die..."</span>

    Yeah, it's that simple but it would decrease case losses if you used a 7-08 sizer as an intermediate step. And it would be helpful to anneal the finished necks for longer case life.

    The necks would thicken about 1 1/2 thou, hardly enough to cause any problem in a standard chamber. In fact, it would slightly improve chamber fit.

    Any slight case shortness would be meaningless.
     
    Re: Forming 260 brass from 308 brass

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">By all means you can make 260 brass from 308, but how in the hell are you going to make it longer, 260 minimum trim length is 2.025, and most chambers that is too short, my trim length is 2.035, most 308 cases are around 2.005, simple easy way is to put Winchester 7-08 brass in a 260 FL die and rock on. </div></div>

    yes what he said.. Use 7-08 and be done with it. Much easier.
     
    Re: Forming 260 brass from 308 brass

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body"><span style="font-style: italic">"Is it as simple as taking your 308 brass and running it through a 260 die..."</span>

    Yeah, it's that simple but it would decrease case losses if you used a 7-08 sizer as an intermediate step. And it would be helpful to anneal the finished necks for longer case life. </div></div>

    And if you use a Redding bushing die it make is simpler, just use some larger bushings to make your step down, rather than buy a 7mm-08 die. FWIW, that’s what I do but I have been using 7mm-08 brass.
     
    Re: Forming 260 brass from 308 brass

    Great posts, great links, how can I add to that?
    I can speak at the 5 year old level:

    *243 necked up to 260 will have a donut at the neck base that can scratch long bullets.
    *260 brass already fits.
    *7mm-08 brass necks down well to 260.
    *308 brass necked down to 260 fits 90% of the time, but the other 10% of the time the cartridge neck is squeezed by the chamber causing a pressure spike. Turning necks is extra work.
     
    Re: Forming 260 brass from 308 brass

    I think you would be better to do it in two steps.

    You going to have to do something to the necks.

    Measure and discard the short cases.
    Measure the thickness and discard the overly thick ones or resign yourself to neck turning.
    Trim to a uniform neck length.

    I'm necking up. I'm not all that happy with my premium 260 brass. It's better than volume brass but the necks are all short. I am necking up a different brand of premium 243 brass, neck turning to get rid of the 'donut' and create uniform neck thickness. The first 50 look good and are within .5 grns case to case weight.

    YMMV