gwpercle, There always has to be contrary opinion so I guess that's where I come in. More guns have been damaged and people hurt by using the "start low and work up" method …. mostly because they don't see "signs" so they keep increasing their powder charge until it's too late …. like taking enough pain killers to make your ears ring then backing off a few. Yes, I have used the "work up" method many times but I never exceed the max listed loads. I much prefer the "factory load" concept as outlined in my library document titled "Mysteries of Smokeless Gunpowder". Here's a link: https://rugerforum.net/e-library/29181-mysteries-smokeless-gunpowder.html
I don't put any faith in "pressure signs" and here's why: The most common pressure signs are hard extraction, cratered primers, and of course damaged guns, which are pretty obvious. For a standard primer to crater, it takes well over 30k psi, considerably more for a magnum primer. This means …. by the time you see primer pressure signs in a 45 Colt you are more than double SAAMI pressure standards, in fact you may well be over the tier 3 limit. Further, all spent primers show indications of pressure …. not necessarily excessive pressure, so you may get false indications. It is very common for factory ammunition to exhibit false primer pressure signs. Point being, primer conditions are an extremely poor way to judge chamber pressure for any cartridge but especially for low pressure cartridges such as 45 Colt, 38 Special, and 44 Special.
Besides excessive pressure, there are two other reasons for cases to be hard to extract, which are …. brass that is too soft or unfinished/rough chambers. It only takes about 10k psi for normal brass cases to expand enough to stick in an unfinished chamber. BTW an unfinished chamber is one that still has factory drill marks/machine marks that resemble threads in a nut …. only much thinner. Again, this is a poor way to judge chamber pressure because you may think it is too high when indeed it isn't. This would put an unrealistic limit on your loads.
Brass will expand and can sieze in a chamber. Why? When a cartridge is fired, both the case and the cylinder expand slightly. When pressure is relieved, the cylinder contracts back to normal but brass cases may not, so they may stick in the chamber. This can cause a false indication of over pressure just because the brass was too soft. One brand stands out in my mind but there are others .... AMERC. It uses a very soft brass alloy that is known for siezing in chambers. Most people do not anneal revolver brass for this very reason. Further, as brass cases are fired and resized, the brass gets "work hardened" so it takes considerably more pressure for cases to stick in a normal chamber. It's pretty common for cases to extract easily when pressure is well beyond max limits. Again, sticky extraction is a poor indicator of excessive pressure because there are just too many variables.
In case people don't know .... the SAAMI max pressure standards for all cartridges were established when the cartridges were designed .... sometimes more than a century ago (as is the case with 45 Colt). Factory ammunition is usually loaded right at the SAAMI max pressure limit because that's what customers expect for performance. SAAMI ammunition pressure standards also drive the gun manufacturing industry because guns have to be designed to hold up to established pressure standards without blowing up or wearing out prematurely. So .... it is a well established fact, factory ammunition loaded to SAAMI standards is safe to shoot (pressure wise) in an unaltered US made firearm. If you are afraid to shoot max loads in your gun, don't ever shoot factory ammo!!!
Here's a much more accurate way of determining max chamber pressure .... rely on established loads in a reputable reloading manual
. Each and every load listed in reputable manuals (Speer, Hornady, Sierra, Nosler, etc) are pressure tested in SAAMI approved labs with very strict procedures. In fact loads tested from one SAAMI lab will be virtually identical when tested in a different SAAMI lab. These max loads do not exceed SAAMI pressure standards and in fact max charges are held well under max SAAMI limits as determined by the manual. In other words, without specifying the exact pressure, one manual may list max 45 Colt loads at 13k psi whereas another manual may list max loads at 13.5k psi, both being well below the max SAAMI limit of 14k psi. Depending on how far out on the limb a manual wants to go, this sort of thing happens in all reloading manuals and at a minimum, it confuses reloaders because max load data will be different. The fact being .... listed loads never exceed SAAMI standards but may be established well under actual max pressure limits, depending on the manual you use.
To take advantage of a reloading manual's data, you must use the same exact bullets, powder charge, and bullet seating depth. If you use load data (powder charge, primer, seating depth) from one manual and a bullet from another (or an unlisted bullet) all bets are off so stay well under the max powder charge.