Trimming samples to meet specific bar length (2500)

Just got the 2500 the other day, ive gotten pretty familiar with some basic functions, but i like to start out with a lead sample, yet most of them are longer than 2 bars and shorter than 4. In Trim mode, it doesnt do a good job of letting me know where the actual bars are at in the sequence. The chop regions are usually off and the loop continues to play over itself. How can I stop this from happening?

I don't fully understand what you are trying to do.

Do you simply want to loop the sample in the sequencer?
If so, make sure the the sequencer's bpm matches the bpm of the sample.
You also have to find the bars in the sample yourself and chop/ truncate according to that. The MPC doesn't do that for you.

An easy way to loop a sample in the correct bpm is to simply drop the sample in the sequencer on the first count. Make sure the the sample is truncated at the one. Count out the number of steps in the sample to find out whether it's a two bar sample or four bar sample. Adjust the number of bars of your sequencer to the number of bars of your sample. Hit the play button. Adjust the bpm of the sequencer untill it loops the sample perfectly.