Having to adjust micrometer down as charge weight goes up??

[Vandy321]

Forster co-ax, 300wm, once fired ADG brass, berger 215 hybrids

Loading for a ladder test. 73gr to 77gr all seated great, measured every one at exactly 2.781 CBTO w/comparator.

Did not touch the redding seating mic...as I worked up towards 78.5gr, I'm having to turn the mic down (seat deaper) to get bullets to seat to same CBTO?

I verified the CBTO readings with COAl and in fact when I set the mic to what had been a 2.781 seat, it would show me almost .005-7 long up towards 79gr. COAL verified that.

I went ahead and seated them all at equal CBTO, just curious is it the beginning of a compressed load that is causing me to have to turn the mic down, or is something up?

 

[Steel head]

Did you feel powder crunching?

I avoid moderate to heavy compressed loads for just that reason.

 

[Country]

Low neck tension on a compressed load can do that .

 

[DIBBS]

Did you check your bullets base to ogive length-variance? As you stated, likely-possibly a compressed load pushing the bullet back out out - maybe need a little more neck tension?

 

[Vandy321]

They're bergers, the few I measured and weighed were spot on. Find it hard to believe my last 3 bullets on a load all happened to be .007-.013 longer than the rest, especially as the case capacity was close to maxed?

.002 neck tension and what should be about a max load, assuming it's just the neck tension/compressed load.

Just wanted to make sure I wasmt smoking crack or had another issue I needed to look at.

 

[Vandy321]

I got them to stay seated finally, if 79 for some reason shoots, I'll up the neck tension, but I highly doubt these cases get past 78 or so without reaching max.

 

[Country]

You may be getting a variation in neck tension due to varying hardness of the necks . A few may not have the full grip .002 usually delivers .

 

[Milo 2.5]

I got them to stay seated finally, if 79 for some reason shoots, I'll up the neck tension, but I highly doubt these cases get past 78 or so without reaching max.

If a hard compress, adding neck tension may be your only option, but neck tension can change the dynamics of all you have tested, so don't just add tension to higher charge loads, do across the board.
One trick for what happened earlier, when seating on slightly compressed to hold depth, when press handle is down, full seat position, let it rest for 5 sec and let the neck adhere to the bullet before coming out of the die with the loaded rd.
I used to really like compressed loads, do not have the time today to mess with them.