QuietTexan
Well-Known Member
Not 100% sure the following applies exactly the same way to the 17 Stinger, but I think it does. For the 6 Mongoose from MDWS (same guy makes both of these) the round is meant to be built from 5.56 brass, and the shoulder moves back during the sizing operation. I set the sizing die with the tallest Redding comp shell holder, and move shorter (sizing the shoulder back more) until the case chambers. The way the shoulder is set it actually bells at shoulder/body junction because the new case has a good bit less taper. There's no need for the false shoulder in this particular case because the initially sized shoulder can be made long by moving it less. The body taper blows out on the first firing, and the overall case length actually shortens somewhat. The initial trim is something like -0.010" from the parent case, but I have to trim to the max spec for fire forming, then trim again to uniform length once the cases shorten as the body blows out. No neck turning because the reamer was built for neck clearance around reformed LC brass that is usually thicker than if you sized down a 223 Rem case.
These are cases that were expanded from .224 to .243 with a PMA carbine neck up mandrel (very nice tool), then sized down in the 6MG die. Sorry this is fuzzy but you can see the belling under the shoulder:
Further back where you can see the belling more as the bright line around the shoulder/body junction from the die sizing the case down:
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