The best thing to do would be to trim back a case until you know what all your chambers are. Start long and go in increments til the brass will let the bolt close. They might only have a trim length of 1.355" listed because 1.360" is about as much length as you're going to get with a 221 case. I remember reading somewhere that the proper way to make 300 whisper brass is with 223 cases.
My 30-221 reamer cuts just past the 1.400" mark. If you listen to the Bench Rest guys a longer neck is better for accuracy as it keeps the bullet aligned longer or something like that. When I start making another batch of brass I'm going to use 223 this time to find out what my chambers are first then find a good length to trim to.
So the correct OAL is what will fit in your chambers.
Nick
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