Didn’t consider the possibility of forgetting to change the caps…definitely a valid point.I've got a 9mm quiet pickle and a hybrid 9mm to .450. I'm sure if you measured it there is a difference but I can't really tell when shooting my handgun. Some hybrid suppressors are made to have different end caps for different calibers but I would be careful because all it takes is to forget to change them when changing guns and you could have a really bad day.
Would be using the 9mm suppressor on pistolsGenerally, if you want to optimize suppression, you will have to go caliber specific. There really is no suppressor that excels at 5.56 and 9mm. I would get one for each. I know it's a terrible answer, but it really is the best and just two isn't so bad. There are plenty of 5.56 cans.
For 9mm, do you want to use it for sub guns or pistols or both?