Determining max pressure without a pressure gun, per Hornady Handbook, third ed., 1980.....
1. flat cratered primers
2. ejector marks or heavy burnish marks on the case head
3. stiff extraction
4. excessive case head expansion (which is determined by measuring the case head just ahead of the extraction groove before and after firing using a blade micrometer or a case head guage). The article goes onto talkiing about what is "excessive case head expansion" with low pressure loads (like 30/30 being .0003-.0004" max) mid pressure(.0005-.0006"), etc. This article does not mention handgun cartridges but gives you a pretty good overview.
It goes onto say that when working up max loads you want to use only new cases as repeated firings work-harden brass at different levels. Makes sense.....!
Don't forget to watch your Minimum OAL as deep seating a bullet can ruin your day!!
For me....I use medium loads that cycle the gun for target, IDPA, etc. and get alot of use from the brass. No problems. For SD I buy appropriate factory ammo, make sure it cycles and use it in the house gun or for CC. For hunting or LR target, this is where the experimentation happens and I am more concerned with using the appropriate bullet for what I am hunting and not so much getting an extra 100 fps out of a "hot load." Varmint hunting is more about accuracy. So is LR target shooting. Ultimately I feel that shooting is about hitting what you are aiming at and reloading is there to help you achieve that goal with cheaper ammo so you can practice or more accurate ammo so you can hit the target at longer ranges after you've practiced with the other ammo to dial in your trigger squeeze, breathing, sight picture, etc. It's all good fun. I highly recommend getting some good reloading manuals and reading them like you would a book. Skip the load data until later. Most are packed with info. Some, aren't so browse them first and get one that has alot of stuff to help you understand what is happening and why.