Neck/chamber clearance, is .002" still in vogue

R

rooshooter

New member
I have been doing more long range shooting lately, where .003" or more neck clearance is becoming common as it is supposed to help ES by ensuring clean bullet release. In my PPCs and BRs, I always ran .002" or less neck clearance, but have been wondering what the short range (100-200 yd) trend is these days. My latest toy is a 6BR shooting 103gn bullets for 300-500yds.
 
These comments were made in July of 1999 and I don't believe they've change one iota in 100/200 yards Benchrest: http://www.benchrest.com/FAQ/2.4.shtml. I use, and have always used .001" to .0015" total clearance in my tight neck chambers, trying to stay closer to .0015" as much as possible.
 
Take a look at the carbon ring around the case neck after firing. If the ring is a straight line, then the neck clearance is insufficient. The ring should dip down on one side if there's enough clearance. This was something I picked up at one of Tony's benchrest schools in St. Louis a few years ago.
 
Clearance

I talked to several good shooters about this very thing at The Nationals, and it does seem that more clearance is in vogue, certainly no less than .0015, and as much as .0025......jackie
 
A number of folks

who shoot 30 Caliber rifles @ Benchrest have been using .003 for a couple of years at least. I re-did all of mine at least two years ago and have had good results so far. I don't know about 6 MM but the necks on 30 cases grow as one shoots them in thickness so I re-turn them after the season. One must be careful not to cut into the shoulder or the loss of the neck will ensue after a firing or two.
 
Breaking in a new Bartlien 6mmBR barrel. Wanted neck clearance close. On a loaded round, it measured .0018. My MV and ES was all over the place. I could not manually push a bullet into a fired case. It occurred to me that necks this tight would not relase consistently, which means erratic pressures, ergo loss of accuracy. I came home and turned necks down another .0006, resulting in total neck clearance of .0027(on loaded round). I am still not where I want to be on the correct load, but I believe increasing the clearance was a step in the right direction.
 
RooShooter
In my opinion consistency is of way more importance than the actual clearance.
To test this out for yourself load some rounds with a fitted neck and some with 0.002 clearance and shoot them at the same aiming point.What I see on my targets is they will make two very distinct groups with each group containg all like neck tensions.
Waterboy
 
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