So I'm already in hot water over on the milsurp thread, so I might as well keep digging! Over the years I've come across various rehashings of the old methods of pressure reading (sticky bolt lift, primer cratering/flattening, shiny spots on case heads etc.) and some of those examples have been right here on this fine website. I am concerned that many folks seem to take this stuff as gospel, when in fact most of it has been soundly dispelled as myth and tea leaves. To wit: Primer reading -- seems to be the most commonly used method, probably because it takes the least effort. It may be the most useless, too. The idea is that a cratered or flattened primer can be a sign of excess pressure: cratering because the primer cup flows into the firing pin hole, and flattening because pressure forces the primer to back into the breech face. The problems are several. First, not all primers are made with the same toughness of material, so a "safe" load -- according to primer condition -- turns into a "dangerous" load when a different primer is used. Did pressures change? Nope. So what did you learn from the primer? Not a thing. Secondly, cratered primers can show up with very mild loads, in a gun with lots of clearance around the firing pin, or even in a gun with a heavy firing pin fall. It's quite common for your old Mauser to put a real splash into a primer, simply because those old military rifles were designed for reliability above all else. This is neither good nor bad, it just is. And those "cratered" primers from Old Betsy don't mean a thing. Now, pierced or "blown" primers are indeed telling you something. Assuming the rifle is in halfway decent shape, a pierced primer should be taken as an absolute indication of overpressure. The question, though, is "how much", and the only answer (again assuming rifle in good shape) is way too much. Something is seriously wrong here, either an accidental overload, incorrect powder, or similar misadventure. A pierced primer tells the handloader to stop right there, back up and figure out what's going on. Then there is hard bolt lift -- supposedly indicating either that pressure is so high that forcing the brass case to "stick" to the chamber walls, and/or that the case head has extruded into the extractor cut and the extruded bit then has to be sheared by the bolt in order to extract (hence the shiny spot on the case head.) The trouble here is that, much like primers, brass cases vary in toughness. A soft case (Norma is a common offender) may well flow at safe pressure levels, while a very tough case (Lake City, Lapua) may not show any sign of pressure until SAAMI specs have been massively exceeded. The case itself is responsible for very little of the strength of the rifle/case combo, so soft cases are just as safe and useful as hard ones. Moreover, the condition of your chamber can make a big difference as well. A rough, pitted, or rusty chamber is going to give you sticky extraction with almost any load. A precise, polished match chamber is going to tell you the opposite lie: that pressures are just fine, even if they are sky-high. (This, BTW, is why you'll find benchresters complaining about loading manuals written by lawyers -- a custom benchrest rifle isn't going to give any of the typical pressure signs until 85,000+ PSI.) And as for the shiny spot on the case head? It's the same deal: soft brass will flow more than hard brass, and a gun with a large extractor cutout is going to show more extrusion than one with a small, tightly fitted one. Going by the shiny spot, an 80,000 PSI load is "safe" in the match rifle, while the 45,000 PSI load is "overpressure" in the old milsurp. Both "truths" are false. Which brings us to measuring case heads. This method was actually used by the reloading manual publishers for many years. It depends upon an experienced user with a blade micrometer, taking precise and repeatable measurements at the correct area of the case, and using the same lot of cases. Few reloaders meet all those criteria, and many who think they do probably don't. Beyond that, there are still problems, like work hardening. Moreover, more recent testing has shown that even loads put together by experienced professionals using this technique have exceeded 70,000 or even 80,000 PSI, which exceeds SAAMI limits for any cartridge I am aware of. It's a slightly better method than the others listed, but it's still no substitute for actual pressure testing. In summation, reading pressure signs is synonymous with pressure guessing, with your rifle -- not to mention health -- on the line. The idea that the hobbyist handloader can learn more about pressure by looking at his cases than the professional ballistician can learn by using several hundred thousand dollars of purpose built pressure testing equipment is dangerous and ludicrous.