Bob; Rule number one....follow your reloading manual for the type and caliber of cartridge and firearm you are loading for! Rule number two....Never fire any gun that you are unsure of...be it for age or mechanical reliability. Rule number three.... Nothing in shooting is a "constant" so, you have to be on the lookout for "all" the signs of high pressure and make a judgement.

Pressure developed by the ignition of a powder charge in a cartridge, when the cartridge is in the chamber of the firearm can only go in a few different directions. Pressure is relieved by the bullet exiting the cartridge and traveling down the bore. The bore diameter only allows for so much pressure to be relieved...the technical term is "bore capacity" or, the ability of the capacity of the bore to burn so much powder efficiently, and relieve pressure so as not to cause a high pressure condition. If you reach the "capacity" of the bore to do that, the excess pressure developed by the overload of powder will seek the path of least resistance. If your cartridges are in good shape, the next path would be the primer flash hole, primer pocket, and the primer. The primer will "give", be pushed out of the primer pocket and be forced against the bolt face, flattening the primer, and release excess pressure, but, only to a certain point. From that point, if the bullet and primer can not compensate for the over pressure condition, the case takes a hit....this is exemplified by the case sticking upon extraction, case head seperation, and case head swelling that sometimes requires prying the case head out of the bolt face, etc. After that point, pressure is so excessive that the excess pressure can do severe damage to the firearm, up to and including a blow up!

Most modern rifles have a "pressure relief port" built into the design, but, that does not mean that you can exceed the safe maximum operating pressure of the firearm, or, that it will save the firearm from damage under a given set of circumstances.

In closing, firearms will punch paper and kill effectively without "maximum loads". A load that is accurate, and carries enough power for the intended purpose is all that is needed. In my 44 Magnums I load a 250 grain Keith at 1000 fps for defense and deer hunting. That is more like a 44 special +P load, but it does the job well, is easy to shoot, and is accurate. Same goes for my 444 Marlin levergun. I use a 300 grain bullet at 1850 fps for deer hunting (the cartridge is capable of driving that same bullet at well over 2000 fps), the load is accurate, easy on the gun, easy on me, and very hard on the deer! If you keep everything in perspective you will realize that loading to the max or higher does nothing for the longevity of the firearm, accuracy, your physical well being, or your pocketbook. If a bigger/faster/ more powerful is needed there is always a firearm out there to fill that spot.