Re: Two more headed home.
Jazz,
Here's the deal, as long as there's no more than .005" clearance between the loaded neck and chamber neck your in the money. Anymore than .005" and you induce run out in the neck during the sizing process and your accuracy goes south and quick.
My main 260 reamer has a .295" Nk with .090” free bore, the Lapua reamer has a .297” Nk with .090” free bore, almost same/same. The 260 Lapua reamer was ordered after the .295” Nk reamer, after the 260 lapua brass came out. My standard 260 reamer wouldn’t work because the Lapua brass was thicker and would cause a pressure spike if used.
I started out building BR rifles for myself and graduated to building them for friends as well. Prior to that I became very proficient at reloading and bedding rifle stocks. My first BR comps were in the factory class and it was during this time that we realized why we were getting run out in our loaded ammo. The factory chamber necks were huge compared to our loaded ammo.
I've checked this on other custom rifles built by others and guess what, it worked the same and for the same reasons.
All the rifles I build have this chamber neck requirement and a custom throat dimension, from the neck shoulder junction south is minimum SAAMI, that’s it. The other part of the equation is the headspace I use and how it's set. Incremental HS gauges from JGS are used for measuring my HS and they run from a true “Zero” to a plus .006”
To some, this may sound like total BS. If so, I'll simply step back and let the rifles speak.
