30 Herrett Help!

[captainkirk]

I have been shooting a 30 Herrett for a couple of years now with several different brands of brass with the same result:  Split necks up to 40-50% of  the time.  I have tried annealing and have gone to a neck die to no avail.  I am beginning to wonder if my chamber is out-of spec.  It is a factory TC 10" scope barrel circa 1978 or so.  The fired cases necks appear slightly barrel-shaped whether they split or not.  Measuring with my plastic caliper the fired ones run around 0.335-337", unfired are around 0.325" (without a bullet). I think the standard dimension given in the manual is around 0.329 (unfired) for the neck but that may be with a bullet seated.  Any ideas?  I'm open to suggestions.

Kirk

[Gavinator]

Did you anneal the 30-30 brass down to where the new shoulder would be before lubing it up and sending it into the 30 Herrett die? How heavy are your loads? Has Remington brass been working best for you?
 I got some fired cases out and measured them, and also had .001" of barrel in the neck (I have not annealed these cases since before they were formed). My cases have been neck turned so it's not from the brass, although the outer diameter of the neck is .337" - .339" (fired), with a bullet seated the neck is at .330".
 Hmmm. how about seating a bullet and seeing if your neck diameter is less than .333"? If it is beg or borrow someone else's cases (also check to see if your powder charge is larger) and see if they split in your bbl..