I trim all my cases with the Lee cutter and lockstud tool, this is very easy and quick. The only time I use my RCBS trimmer is when I load Cast Performance 440gr LBT bullets in my 45-70, I must shorten the cases .060 before they will chamber in my Marlin 1895. I like this bullet well enough to justify the extra work. But the Lee system is fool proof and consistent. I sometimes will turn case necks, but I'm still not sure how much it helps. Cartrige oal is a variable that affects some rifles more than others, I usually seat my bullets just short of the rifling and all is well. The most important thing I can do is use quality components. Most of the time the tightest groups will arrive before maximum pressure does. when the gun and load are tweeked ,you still must do your part,a good concrete bench and a solid rest are important.