OK guys, I have my father's and before that my Grandfather's Remington 12 ga. mod 11A (1919). As long as this shotgun has been in my family, it's shot modern-high brass shotshells. Now I've ordered black powder shells https://www.buffaloarms.com/12-gaug...1-8-oz-7-1-2-shot-25-rounds-per-box-amogx12ga to use in the gun. As someone pointed out in another thread, these older shotguns may have something other than a 2 3/4 in chamber. I have no idea the best way to measure this chamber, however if I were to take a fired modern shotshell from this shotgun, and measure the overall length(my understanding is the length is measured from an open shell-not a crimped one), would that tell me what I need to know about the shotshells I purchased? Or for shotshells I plan on reloading? Any help is appreciated. Thanks.