When are you trimming? Pilots are usually sized to trim fired/unsized brass. If you are trying to trim new/unfired brass you might try running them into the expander die first. If this doesn't you can either laod and shoot them as-is, or polish the trimmer pilot so it is a good fit in the sized and expanded case.
I prefer to trim after sizing & expanding so the length the case is trimmed to is the length it goes into the chamber. Try this exercise and you will see what I mean:
Start with a new/unfired or sized case, mic. the length and record it.
Load and fire same case, mic. and record
Size, mic. & record
Expand, mic. & record
Now, compare the measurements. Amazing how the length changes, isn't it? The only dimension you can control precisely is the sized and expanded length. This is why I like to trim at this point as it gives the most consistent length for crimping.