The Wilson Pistol Max Gauge is set for Max SAMMI Specifications. It seems that 9mm is all over the board with chamber size with a lot of them bigger. However, a gun with a minimum chamber can still fail to feed a round that passes the Wilson Test.

When I loaded 45ACP for matches I used one brand of brass and always continued to load the same brass over and over. The same with my 357. I always checked them with the chamber gauge as a final quality check. Mostly the problems I found were split necks that were not discovered in initial inspection that were expanded during belling and seating. You can feel the crack when it enters the gauge. When you are shooting, especially in a match, it is not the time to find out that a round won’t feed. I don’t shoot matches much anymore, but old habits are hard to break. I can't recall a checked round fail to chamber in my guns.

Initially I think I will start out with a single brand of brass (FC) and stay with those that were fired in my gun to develop my load. I will continue to collect range brass just because, but getting brass for 9mm is relatively cheap even if you must buy factory ammo.

With such wide variations in brass and chambers, ‘plunking’ each loaded round sounds like a good idea especially if using mixed pickup brass unless, of course, your gun is capable of shooting pinecones 😉.