please tell me i dont have to trim,

[Cossack]

It sounds like shoulder location was more a problem than case length. Since cases grow at differnt rates, it's important that you can measure them after sizing regardless how you size. Neck sizing alone will not prevent your cases from growing. Even when necksized, a case that is too long can create pressure spikes if it extends into the lead. And while it may or may not be dangerous, it won't do anything for accuracy. So cases need to be checked that they don't exceed the max OAL for your rifle. And, since accuracy is a matter of uniformity, I think it's best to start with cases that are all the same.
Sinclare does make the Comparator that measures max case length at the shoulder
as well as cartridge OAL at the ogive. They are seperate tools that attach to a caliper.
Lyman also makes guages that measure the max case length of most cartridges. Or you could make one yourself using a piece of aluminum or even plastic and a file.