The simplest way to tell if you're running too tight in the clearance department is to look at the carbon ring around the neck after the case has been fired. If it's a line that goes straight around the neck, then you aren't running enough clearance. If the carbon line drops down on one side, then you are. A bullet won't slip into the neck of the fired case unless you are using way more clearance than I'm running. My reamer cuts a .2655" neck most generally. I'm turning for a .0102" thick neck, just because that's where I got the neck turner set when I was turning necks. My boat tail bullet measures .2432". .2432" + .0102" + .0102" = .2636" for .0019" clearance on the .2655" chamber neck. The reamer is marked for a .265" neck, but cuts a little oversize. It does give the sine wave type carbon ring around the neck when its fired. I turned some brass last week for a .0096" thick neck and it didn't seem that they shot quite as well as the slightly thicker brass. But, to be fair about that I didn't try a tighter bushing to size the brass more to match the same seating pressure that I was using with the thicker necks. Brass thickness is a pretty simple thing to experiment with to check. What someone tells you or what works for someone else may work well with your rifle or it may not. Chambers are different, leades are different and what works for one may not work for all. I've been shooting the borerider reamer almost exclusively for the past year and started out with it this year. Bill Summers is using a reamer based on my same reamer print and he's finding the same thing that I am with it. That is that the freebore seems to take out seating depth out of the equation as it's pretty seating depth insensitive, but you have to make up for it with seating pressure. Not sure whether taking seating depth out of the equation is a good thing or bad thing. I'm not fully committed yet to this reamer. Time will tell, but so far I haven't seen a reason to quit using it.
Best thing you can do when shooting benchrest is to spend a lot of time at the range and find out what works the best in your rifle. Get the bugs worked out of your system. Sizing die matching your chamber, where you don't have extraction problems with hotter loads. That kind of thing. I'd also suggest shooting at the range with a timer just as if you were in a match. One of the most critical things I've found is when you choose to start shooting your group during that 7 minutes. Start in the right conditions and you'll do well, start in the wrong condition and you'll struggle.
