Depending on the bullet weight and style of bullet (ogive),will have alot to do with the OAL of a given cartridge.
Most are 2.250",but they can be shorter or longer depending on the bullet used,and what the mfg specs it for.
If your reloading,you can do it by the book,or get an OAL gauge and measure your chamber depth.This will tell you just how far out that a bullet can be seated to the lands of the barrel rifling.
I do this for each bullet size/type that I reload for.Now,you will find out that on some guns,the OAL will be a lot longer than your magazine length,so if you load the bullets long you will have a single shot rifle,and only be able to load 1 shell at a time into your gun.
For target rounds this isn't a problem,but if you are planning on having more than 1 round in your rifle,you will have to seat the bullets in atleast to the length of the magazine.
For example,My RRA AR15-The longest that I can stretch the length of any cartridge to fit into any magazine is 2.260",but if I want to shoot my 77gr Sierra Matchking bullets they're too long and won't fit into the magazine,so I have to load each bullet into the chamber by hand.
But with my Savage 12FVLSS,I can load them into the magazine because I modified the length of the magazine.