No-Neck Turn Chamber Measurement and Reamer Size

[artbosco]

Assume a case has a bullet seated in "Lapua" brass and the outside dimension measures .268 inches.

What size should the neck chamber measure to provide a "safe clearance" for a no-neck turn chamber ???

Should it measure .0015, .002, or .003 larger ???

What reamer size should be used ???

I ask this question because I've read somewhere that reamers tend to cut a chamber a tad larger than the reamer's actual size.

I'm looking for a "no-neck turn standard" that can be applied to any caliber that uses "Lapua" brass.

Thanks for your response.

Happy New Year to all.

 

[HTSmith]

My loaded rounds mike .269 and the neck on my chamber is .271. I was concerned about that being too tight, but it has worked great. Very little working of the brass and its extremely accurate with Lapua brass right out of the box.

 

[Mark Walker in TX]

Art,

Typically, if there is such a thing, one would go .002 above loaded round diameter.

With the 6BR, using Lapua brass, most see loaded round diameter of .2695 or so, and most go with a .272 when ordering a no-turn reamer.

 

[treeman]

About a month ago i purchased a reamer from ptg the neck dia. is .272" After i chambered the barrell i did a chamber cast and it cut dead on .272. this was the dia. that dave kiff recomended. treeman

 

[Preacher]

If a reamer is dead on center and the chamber that is being cut has NO run out, how can it cut a bigger chamber ???

 

[artbosco]

Preacher: Good point. That's why I asked the question. To debunk what I thought I read. Thanks.

 

[artbosco]

Gentlemen: I called Dave Kiff at Pacific Tool and Gauge today. He recommended the reamer be .0025" to .003" larger than the case-with-seated-bullet outside dimension when using Lapua brass. Thanks to all for your help and comments.