I documented the same thing observed by Stan Watson (that traditional pressure signs do not usually show up until pressure is too high already) in an article for HANDLOADER several years ago. I even found measuring case heads an iffy proposition.
In that case I worked up loads for the .22 Hornet, .270 Winchester and .30-06 using both traditional signs (bolt lift, primer appearance, case head marks, primer pocket tightness) as well as measuring case heads. Then I had them pressure-tested on piezo equipment. Some turned out OK, but some turned out way off. The .270 loads, for instance, averaged around 68,000 psi.
Since then I have continued testing along the same lines and decided that measuring case heads is just as erratic as traditional pressure signs. Have measured new belted brass from two different major manufacturers that expanded .004 and .02 inch with THE SAME LOAD, and the brass in each case weighed just about the same from both makers. Now, how can we tell what pressure we're getting from an arbitrary case-head measurement if you consider that?
Have found that you can come reasonably close to the same pressure as factory loads if:
1) You shoot some factory loads, and average the case-head expansion.
2) Pull the bullets from the rest of the factory loads, then work up handloads to the same amount of expansion.
Most of us don't do it that way, though.
Also, keep in mind that when the 7mm STW was turned into a factory load, Remington tested several "standard" handloads that had not created traditional pressure signs in custom rifles, and found that almost all were above 70,000 psi.
JB
