How much neck clearance is too much?

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Well-Known Member
Oct 15, 2020
I'm having a barrel chambered in 30 Nos and it looks like the saami reamers are .346.
I'm using Peterson brass (bought a ton of it for a deal) and loaded neck diameter is only .340
Neck thickness is .016 so pretty standard

So with .006 neck expansion plus .002 neck tension when sizing, I'll be working the necks .008 every firing.
Is this gonna give me neck splitting issues?
I've never had a chamber with more than .004 neck clearance
You should be OK..

The .008" from fired to sized is maximum, if using a bushing die. (Redding info). My 243 win turned brass is worked the same .008" But walls are not as thick as your brass.
Over 20 loading on 2 lots of brass.
It is working necks a lot.
Tricky sizing for planned 2thou interference too (due to excess sizing angle).

I suppose it works for folks, but I wouldn't put up with it.
Have the barrel chambered with a better reamer if you can. Just fill out a reamer print and order one.
These groups are all shot with .006 neck to chamber clearance with .0025 neck tension. I don't think you can ask for much more from a 308 Norma Mag hunting rifle. I have brass with 6+ firings on it and zero issues.

You're not getting good results -because of excess neck clearance.
You won't be getting good results -because of high runout.
You won't be getting good results -because of high tension variance or cracking necks without constant annealing.
And you won't get good results -because of lower/normal neck clearances, even while easier to manage.
Some of us, with certain shooting systems, will not get your results -no matter what we do with neck clearances.
Some of us, with certain shooting systems, will better your results -with different neck clearances.

So, I cannot think of a meaningful way in which your pictured groups relate to neck clearances..
That's just me probably
My point is, having neck clearance that you think is too excessive doesn't affect my accuracy or consistency. You say you wouldn't put up with it and you would rechamber the barrel. But why? Where's your data and your results? I showed mine. The OP doesn't need to throw money away to feel good about having tighter neck clearances. You can get good results, as I showed, with the same clearances the OP has. If starting from the ground up, having a reamer made to your specs and having everything exactly how you want is good. We all have things that give us confidence and make us feel better, but they don't always make a significant difference.
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