Expander Mandrel Causing Neck Runout

[Zia Hunter]

Thanks for all the posts and think I have the issue solved with all your suggestions as well speaking to the wonderful tech folks at Sinclair. First of all, I fired the cases with excessive runout and they have less than 001" of runout after firing. The problem was with the FL sizing die and not the mandrel. Will need to run the expander mandrel on new brass first then trim, debur, chamfer and neck turn. Once fired, will neck size without expander ball and decap only. Ran some test cases and runout was less than .001"

The Swift will flow brass into the neck and sometimes will need to be turned after a couple of firings. The problem with turning fired brass is the expanded neck won't snug up to the mandrel. My options are either to neck size then expand with a mandrel or turn with a Forster neck turner. In speaking with Sinclair, my Redding Comp die set will not work in this instance and will require a different neck die. The Forster turns necks after sizing so that is probably my best option. Not as precise as the Sinclair but still ok.

 

[Country]

country: " I rekon the case necks are too hard and need annealing". We're talking about new, never loaded RP brass, that has never been subjected to work hardening. I find it hard to believe that virgin brass would need annealing. Zia Hunter: I also get case neck runout anytime I run an expanding mandrel into a case neck. Just necked up a small number of new Lapua 6BR to 30 cal., using Lapua, and typical R/O's measure .004" to .006" on my Sinclair gauge. At this point I really don't care. They will straighten out with the first fire-forming. There may be an occassional one or two ( out of 20) that will always have some slight R/O for their entire life, compared to the others that will be less than .002", but I write those few off as having a slight defect since the time they were formed. If I feel accuracy may be compromised by these few, I keep them for first round foulers, basic scope adjustment & 100 yd. maximum distances, where I find it to not matter. Actually have gotten some very excellent 5 shot groups at 1 and even 200 yd. with R/O's as much as .004". Works for me.

I know it is unusual but new cases can be left unannealed after forming and sometimes can be harder than others. If the brass is also thick it makes is worse still.
That is why lapua do not polish the outside of the case to remove annealing marks to show the customer that the last process was annealing. Just because they are never loaded before does not mean that they are new production . Brass age hardens as it sits around for years . It also hardens while under tension such as when a bullet is seated it takes years but it does happen and in varying degrees according to storage conditions and how hard it was to start with and any contamination such as Amonia or other Amines.