Neck Tension

[jeffm]

I just got a new 308 barrel that is marked .342 neck. The good folks of the hide educated me to what the .342 neck means, but it opens a hole new area for me to explore. It is my understanding that the .342 is not a tight neck, but if I had chosen a tighter chamber neck and had to turn the case neck for the tight fit, how much clearance would the neck require? For example, lets say that .342 was a tight neck, about how many thousandths would I want my case necks to measure for max accuracy. Does the amount of clearance needed change for different calibers? Or lets say my case necks start getting to fat. At what diameter do I need to ether trash my brass or invest in a outside neck trimmer?

 

[FCS]

Re: Neck Tension

Loaded round neck diameter for a 308 Win with Lapua brass is about 0.339", with a 342 neck diameter you have 0.0015" clearance / side.

Loaded round neck diameter for a 308 Win with Win brass is closer to 0.336" so you have 0.003" clearance / side.

I consider loaded neck diameter of 0.003" smaller (0.0015" clearance / side) than diameter of neck in chamber to be minimum for field / tactical rifle.

Loaded round neck diameter of over 0.340" I'd start turning the necks.

 

[Fuzzball]

Re: Neck Tension

As with many things about reloading, it's largely up to the loader to set his own measurement for tight neck clearance. I mean, there is no "standard" measurement that MUST be achieved, other than the obvious that there MUST be some clearance!

 

[FCS]

Re: Neck Tension

So, what do you recommend as a minimum, reasonable amount of clearance?

What are you basing this minimum on?