I have some brass that is 1.755". Is that too long? How do I know what is too long? Thanks.
dmazur's comments are good information.
To add, in general, there is a published maximum length for cases. For a SAAMI accepted cartridge, all chambers cut to SAAMI standards should accept cases at this length without problems.
Due to manufacturing tolerances, chambers may accept longer cases, but it is not a good practice to routinely allow cases to grow longer than this published maximum length.
The rule of thumb is to trim cases to 0.010" below the published maximum length. This allows for a few to several reloadings before the case exceeds the maximum published length.
Cases could be trimmed shorter, and a few thousandths of inch won't hurt anything, but again, it is not advisable to trim too short.
Cases any where between the published maximum length and the "trim to" length (nominally 0.010" below the maximum) are safe and fine.
Some folks like all of their cases trimmed exactly to the same length and trim them even if they do not exceed the published maximum length. There are valid reasons to do this for specialized purposes, including the reloader's preference. Generally, this level of precision is not necessary for most shooters.
So, the short answer is, when a case exceeds the published maximum length, trim it. Trim it to no more than 0.010" less than the published maximum. But, not trimming to 0.010" less will mean you may have to trim more often.
For non SAAMI cartridges there are no published maximum although the developer may have a figure in mind. It is best to have the chamber measured and make adjustments from there. Once a max length is determined, the 0.010" trim could be used.
For me, I have cut a caliper like "go-no-go" gauges for my cartridges. The gauge is cut to a couple thousandths of an inch shorter than the published maximum. If a resized case fits the gauge, it does not get trimmed. If it fails to fit the gauge, it gets trimmed. A caliper could be used to do this measurement but I have a thing about handling precision measuring tools more than necessary. (Butter fingers, you know)
Hope this helps and makes sense.