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40 90 Sharps Bottleneck

billomike
Good day all,

I recently purchased 100 cases of 40-90 SBN made from 348 Winchester cases. Loaded 90 grns of Pyrodex ffg against 430 gr paper patched, base cupped, .399" dia lead bullet. Bullet snug+ fit at muzzle. Bullet seated against rifling minus a few thousands inch. Mag large rifle primers. Loads for original Sharps 40-90 SBN model 1874 in excellent condition - both bore and chamber (no cast taken). The first trial shot - resulted in case seperation 1/4" ahead of rim - not complete, but pretty obvious circumference failer. The case expanded apprx .016" forward of the fracture compared to unfired loads. Shoulder dia normal. Primer slightly flattened and approximately .002" protruded beyond shell base.

I would certainly welcome opinions on the case failer.

Best regards all.
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Comments

4 comments

Date Votes
  • 44caliberkid
    Perhaps you need to fireform the cases with a reduced load, then just neck resize. Like 40 grains of 2F and corn meal filler.
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  • billomike
    quote:Originally posted by 44caliberkid
    Perhaps you need to fireform the cases with a reduced load, then just neck resize. Like 40 grains of 2F and corn meal filler.


    Thanks for the suggestion. "corn meal filler", not heard of that before. It will be interesting to apply. Measurements of before sized brass, sized brass and the fired/seperated case suggest fire forming is in the near future, with 40 gr's it will be. I did try a fire forming experiment, by reducing to 80 gr - and hand press fit the round tight against the lands with the pp bullet only snug in the case. That experiment failed as the case seperated entirely at the same location where the first only gave incipient sign of failier. I'll report back on 40 grains - corn meal. Thanks again.
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  • jonlower
    Give up on the 343 Winchester cases, they are the problem. Go to Buffalo arms and buy some 40-90 cases and make a chamber cast. You may have an oversize chamber from that little engineering problem they had at one point. The 348 case wall is too thin to compensate for it.

    JP
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  • kspair
    You may have a headspace problem...the rims are too thin. If you have a Shiloh or other modern rifle, they are reamed for thinner rims than the originals. Make a determination by chamber cast and order brass accordingly. As mentioned the .348 is not a suitable case to make the long 2 5/8 in case.

    Anytime you mess with a 40-90, 44-77 or 44-90 always does a cast first then order your brass, bullets, and molds or you'll find your self in a deep money pit.

    Don't ask how I know this.[B)]


    What is the bore diameter of that rifle. A .399 would wrap up to at least 406. Shiloh 40 cal are .400 bore and .408 groove.
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