Any time you see a ejector mark on the base of the case it means the pressure was so great the brass flowed into the ejector hole. This means the brass stretched beyond its elastic limits for that brand of brass. And if you took a before and after measurement of the base diameter just above the extractor groove you would see a increase in diameter.
Bottom line your brass will not last as long and your primer pockets will stretch out of shape.
Below is from accurateshooter.com and this long range shooter increased the load until he got brass flow into the ejector. He then backed of the load 1 or 2 grains after finding the elastic limits of the brass. And ejector marks vary by brass hardness and Lapua is noted for having harder brass.
Simple Trick for Monitoring Pressure of Your Rifle Reloads
http://www.hodgdonreloading.com/rel...-trick-monitoring-pressure-your-rifle-reloads
I've used the method described in this
Just looking at fired cases will not give you an accurate reading.
The only way we reloaded have a judging pressures is by measuring a factory case fired in your chamber with a 0.0001" micrometer.
When you fire several cases of factory ammo, measure your case expansion , average this number.
When you are starting with your minimum load and working up, measure your fired hand load with the 0.0001" micrometer, once your hand loaded cases expand the same as your factory cases then you have reached the maximum load in your chamber and components.
I have been wondering if anybody was doing this any more, and I'm glad you brought it up. This is very much like the old "copper crusher" pressure measuring method that used to be the industry standard. I've been doing this for decades, with a blade micrometer. ( A regular micrometer won't work; the posts will hang up on the rim of the case and the expansion ring on the case wall on the other side. The spot in between that we want to measure - just ahead of the extractor groove - will not be in contact with the faces of the posts of the micrometer.) I also C-clamp the mike to a flat surface, and stand the cartridge case on top of the calibration washer for the tool, so that I will uniformly measure each case at the same height above the head
every time. Repeatability is key.
Employing this method, the blades of the micrometer touch the case walls immediately above the extractor groove, and I do it at a mark I have made on the side of the case with a black magic marker. ( These cases are not always perfectly round, so measuring at the same spot on the circumference is critical to the accuracy of this method.) I write the measurement on the case with the same marker, so that I know what I'm comparing to after I shoot that round.
I have read Hodgdon's manual on this, as well as an older Hornady manual. Dave Scovill also wrote this up years ago in Handloader Magazine. Others have commented on it, and it was once considered SOP to do this. ( NICK HARVEY'S PRACTICAL RELOADING MANUAL devotes a whole chapter to it. ) The general consensus is that with the 30-06 case head, .0005" of expansion is maximum. I've also found that most factory loads expand around .0003". So, I have determined that .0005" is
absolute max, and .0003" has been my "in the field" max or "hunting max." When I load to .0003" of case head expansion, I almost always find velocity to be very close to factory load velocity, and I've never had an issue of any kind at that pressure level. I'm now considering "splitting the difference" and just adopting .0004" as an all-around number to work with, and just let it go at that.
The whole story here is that these measurements are not telling us actual pressures, but relative pressures.
Relative to what ? Relative to what the bullet, powder and ammunition manufacturers have found with their fancy testing equipment using min-spec pressure barrels. That's why I think that going to .0004" expansion is probably not going to cause me any problems in the field. Having road-tested the .0003" value for twenty years, I'm ready to move it up a notch -
but not two notches. That last .0001" is my safety buffer.
Speaking of two notches above factory loads, Scovill's article showed that his .0005" expansion coincided very closely with 60,000 PSI when he measured pressure using both his method with case head expansion concurrently with some bullet company's pressure-testing equipment. Just throwing that out there for you guys to chew on, if you're so inclined.
Lastly, I'd like to say that I'm a bit surprised that this method has fallen from favor, or at least doesn't get talked about much. It seems to work pretty well, but I must admit that it may a little conservative for most guys, and it is kind of a pain in the keester to do.