SmallCaliberCentral

How Much Of an impact does neck turning have? How Many of you do this?

Neck turning for a SAMMI factory chamber is meaningless unless your brass has so much neck thickness variation that it requires it. In that case, the brass is scrap anyway so why bother? Cleaning up necks 30% or so can make a minute difference, but usually not worth the effort required.

However, for many custom chambers, neck turning may be necessary just to chamber a cartridge if chambered for "tight neck" specs. My custom chambers usually get the necks turned at least 40-50% just to clean-up the high spots, especially after forming from another caliber, necking up/down, etc., as the neck thickness almost always changes during these ops. For example, my Sako/Shjilen .17 Mach IV and my Ruger No.3/Pac-Nor in .17 Ackley Hornet require 100% neck turning to a specific thickness after forming their respective brass in order to even enter the chamber.

Here's some freshly formed, annealed and neck turned .17 Mach IV's loaded with WS2 coated Berger 25gr Match HP's. The freshly done neck turning is obvious:



Most 204R chambers have a SAMMI neck I.D. of .232". I have a custom 11-twist barrel chambered with a custom reamer with a "no-turn" neck, meaning the neck I.D. mic's .230", my loaded brass necks mic exactly .228", so the bullet has .001" per side, or .002" total for safe bullet release and requires no neck turning, but has a semi tight neck by factory standards so the bullet is more perfectly aligned with the axis of the bore, and not "laying at the bottom of a sloppy chamber" so to speak. This is one advantage of headspacing on the shoulder, and neck sizing only for the best accuracy possible.

Oh, and that custom 204R 11 twist 3-groove Pac-Nor SS Super Match barrel does indeed shoot bugholes so chambered that I'm able to touch the lands if wanted. HTH