.308: What do you recommend as the optimum neck thickness?

[Campbell]

I am learning how to neck turn and I am being conservative with the amount of brass removal. Probably too conservative?

The necks' surfaces are approximately being effected by 50-60% and the necks' thickness is .015".

Please will you advise!

Many thanks in advance.

Cam

 

[JasonT]

I turn my Lapua 308 brass to .0135"-.014" thickness. That's usually a 90%+ cleanup. Basically I'm skimming .0005"-.001" off the neck.

 

[CJ6]

.003-.004 (loaded round) LESS than chamber neck dia.

 

[ShootDots]

When I order a reamer, I order it with the idea that I will have turned the necks to 12 thousandths thickness. All my necks are turned to that. I have found that if you do that and anneal your brass, using bushings that cause 1 and no more than 2 thousandths neck tension, your bullets will seat like smooth butter, with great consistency.

 

[eric32]

I ran a test recently with some really good results.

Cut in .001 increments

I did 5 case all the way from .015 to .010

Then fire each case and see wwhich thickness has the best ES.

 

[calgarycanada]

I ran a test recently with some really good results.

Cut in .001 increments

I did 5 case all the way from .015 to .010

Then fire each case and see wwhich thickness has the best ES.

And the result was ?

 

[eric32]

I still have to do more testing but .333 loaded round with .003 neck tension was the most consistent.

I cant really measure the neck thickness right now until i get my case neck gauge in. But my best guess using some math is .013 thickness

 

[a1712]

I ran a test recently with some really good results.

Cut in .001 increments

I did 5 case all the way from .015 to .010

Then fire each case and see wwhich thickness has the best ES.

How are you checking thickness with no way to measure thickness. Not trying to be an arse, just curious. Brian.

 

[eric32]

.307 expander

.330 unloaded round

.333 loaded round

 

[eric32]

Got a case neck gauge and all the brass that shot with the lowest es was .015 thick.

Something was off on my math i dont think i accounted for brass spring back

 

[Boatschool02]

0.010-0.015" neck thickness in what size chamber? (i.e. were you really seeing performance variance due to the brass thickness or that specific size overall loaded rounds performance in a chamber better suited to the thicker brass?) IMHO, it sounds like your test (unless you ran it across five barrels with similarly descending neck diameters) may be better suited to optimizing loaded round chamber clearance for your reamer spec than determining optimal brass thickness.
-
When I talked to John Whidden about this, he recommended turning to 0.125". On my Lapua Palma brass, I saw what I'd consider a full clean-up in the 0.013-0.0135" range based on loaded round measurements and tube mic thickness measurements using 0.0001 Mitutoyo gear.
-
Two very accomplished shooters whom I trust told me not to go under 0.004" clearance with this caliber and 0.005" would be just fine. I prepared brass for a 0.3355" loaded round in a 0.340" chamber and look to test shortly, but even this won't really answer the OP's "optimal thickness" question. I would defer judgement to some experienced FTR shooters who might have tried various thicknesses across multiple different reamers.

Luke

 

[eric32]

Chamber was a sammi spec .3433

I by no means would ever say that one specific neck thickness was the best.

What i said was a i ran a test which different neck thickness and loaded round clearances. And .015 with a little bit of give and take. Was the best for me.

I was just stating my findings that pertain to me and not make any blanket statements about which one is trueky the best.

I think every brass brand has it own optimal thickness and clearance along with powder selectio. And neck tension that makes it shoot. No many variables unless you test in your rifle.