Turning necks for a factory chamber?


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benzy2
November 6, 2008, 01:28 AM
Ok so I understand the benefit of a concentric neck and turning necks to get this. My question comes to the chamber the round will go in. Most of the neck turning I see is for rifles with a chamber cut that has a tighter neck than that of factory brass and as such the brass needs turned to fit. If I am using a chamber on a factory barrel that isn't a tight neck do you still want to turn necks? I had heard you only want .001-.002 clearance between the neck and the chamber wall. Is it better to have a concentric neck or to have one that fits closer to the chamber wall? Do you want to just touch them up until the hit concentric and then stop or do nothing to them at all? I am looking for a little more accuracy now and thought this would be the next easy spot to look.

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.38 Special
November 6, 2008, 01:34 AM
You won't generally get a whole lot of accuracy improvement with turned necks in a factory chamber, unless the necks were really out of whack. IMO it's a fine practice to just "clean up" the necks -- removing material from 60-70% of the neck -- and call it done.

That .001-.002 clearance is in reference to "fitted" necks, where the neck is allowed to expand just enough to release the bullet upon firing, but not enough to permanently deform. This allows the shooter to reload without sizing, and encourages long brass life. It's also dangerous, only for experienced handloaders shooting benchrest rifles under controlled conditions and being extremely careful about maintaining clean chambers. A bit of grit between chamber and neck can severely spike pressures in a fitted gun. Not to mention the potential disaster of fouling up your arithmetic and managing .000 clearance!

FWIW, one old trick with factory rifles is to form cases from a larger case. This leaves you with a thicker neck wall and allows you to turn to whatever thickness/diameter you are looking for.

Have fun!

Walkalong
November 6, 2008, 08:15 AM
Mostly a waste of time with factory chambers. In fact, it can cause problems. You would have to experiment and see. A chamber cast would give you a great idea if it is feasible with your gun.

FWIW, one old trick with factory rifles is to form cases from a larger case. This leaves you with a thicker neck wall and allows you to turn to whatever thickness/diameter you are looking for.

Ditto. I had forgotten about folks doing that. Good point.

USSR
November 6, 2008, 08:19 AM
it's a fine practice to just "clean up" the necks -- removing material from 60-70% of the neck...

I do this with Lake City M72 Match brass. What you are basically doing is uniforming the neck thickness for uniform neck tension purposes.

Don

243winxb
November 6, 2008, 09:56 AM
http://www.thehighroad.org/showpost.php?p=4917169&postcount=16 Outside neck turning for a factory chamber is just something you have to try as the results vary with different guns. You should start my taking measurements of the fired case neck with a micrometer. The fired case neck average measurement should not be larger then .002" when compared to the loaded rounds neck diameter. http://www.stevespages.com/page8d.htm A 243win neck is .276", my fired case should not be larger than .278" if i want to neck turn for that gun. http://www.thehighroad.org/showpost.php?p=4923115&postcount=30

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