Modified case jig

[landonm]

The .270 case I did was +.006 and the case base was square.

Interesting. I'll have to do a bit more testing on my side and see if I can figure out how to replicate. One way to eliminate the case stretch to maintain absolute accuracy would be to size back down and bump the shoulder back either without the bushing (if using a bushing die), or FL size it and open the neck back up with a 7mm ball or expander mandrel. I think most guys are using the OAL gauge more as a reference point rather than an absolute. In those instances .006 wouldn't matter much as long as you're loading for a jump more than .010 to avoid tolerance stacking and accidentally kissing the lands.

 

[MarkInPA]

I gave up on this jig a long time ago. I don't need no special modified case nor do I even need the Hornady, Stoney Point tool to determine my head space dimension.

All I need is a bullet, a case with the neck slit, a comparator, and my calipers. No drilling. No thread cutting. No special jig.

For me, it was money I wish I spent on either powder or bullets.

 

[Jester896]

Interesting. I'll have to do a bit more testing on my side and see if I can figure out how to replicate. One way to eliminate the case stretch to maintain absolute accuracy would be to size back down and bump the shoulder back either without the bushing (if using a bushing die), or FL size it and open the neck back up with a 7mm ball or expander mandrel. I think most guys are using the OAL gauge more as a reference point rather than an absolute. In those instances .006 wouldn't matter much as long as you're loading for a jump more than .010 to avoid tolerance stacking and accidentally kissing the lands.

on both of these I used a Mo's Gauge for my measurements. It is basically a Wilson case gauge that has been modified to accept a mic thimble. When we make one ourselves we borrow a thimble and set the zero with a go Gauge.

I'm wondering if what is doing it is the tension that I use on the die. Any time you squeeze the sides of a case the only real place the brass can move is up. Kind of the same thing you get when the datum area of the die doesn't contact the datum area of the case and you end up with an improperly sized case that is too long for your chamber now.