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.

 

[tightneck]

.0015" over loaded neck diameter is fine IMO, but how do you know that the next lot of brass will measure the same as the stuff you have now? I don't think that it does much good in most applications to have this little amount of clearance either. If you are talking about the 6BR, then a .272nk or .273nk is standard for a no-turn. Err on the side of more clearance, and you won't have any worries down the road.

 

[fdshuster]

My loaded neck dia. with Lapua is .2685"/ .269". The Pacific reamer cut a .272" no-turn neck: no problems.

 

[Rust]

For a rifle shootin long strings I prefer .003". Going .004" wouldn't hurt either. One thing to keepin mind is that different brands and lots of brass may vary in neck thickness.

One thing to keep in mind is that well prepped brass that is loaded straight with the bullet into the lands, the neck of the case is not supported by the chamber anyhow. To me the primary benefit of a tight not turn neck is not working the brass and a faster better chamber seal from the neck.

 

[therifler]

no turn neck .004 thous. if reamer cuts big by .001 no trouble have been building guns for benchrest and winning with this neck size . www.therifler.com