Trimming less then the recommended length really isn't problem other than a little more gap space, the distance from the case mouth to the start of the freebore. Its one of the places powder residue and burnt oil (carbon) can buildup and should be cleaned the same time as the bore. Of course the smaller the gap the less room there is for the crap to collect and buildup.



You can see the where the case mouth would be compared to the chamber cast. Its also easy to see why trimming is necessary. If the cartridge neck was too long when a round is chambered the "Step" or the start of the free bore would essentially crimp the bullet then ugly things could happen!

Bill