Home Forums Hunting & Shooting Gunsmithing Neck clearance?

How much neck clearance is generally needed for good bullet release? For example if a loaded round is measuring .3165" around the outside of the neck and a fired case is measuring .319" and the reamer neck spec was .319" is that enough clearance only having .0025" or will that cause problems?

Thanks,
Bb

Any clearance is enough. In benchrest they work with .001" or less. Just as long as the bullet releases. Problem with tight clearance is if you get a lot of brass with thicker necks it can be dangerous.

That neck diameter measurement on the fired case isn't an accurate indication of the actual chamber. Brass changes dimensions once it cools. A chamber cast will produce a more accurate result.

the clearance you have is fine, would be a good idea to moniter neck thickness of your brass especially when using new brass. i had a 6 ppc with fitted brass that would release bullet but spring back enough to hold bullet,this is common in benchrest.

Ed

Very few benchrest shooters, that I know, use "fitted" necks. Most opt for 1.5 to 2 thou. clearance.

Amen, Eddie. I don't know of anyone that runs less than .0015 total. I start at .002 and have found gains in several of my 30BR's and 30X47-ish stuff by being in the .003-.004 range.

Good shootin' to you and Sara this season! -Al

if fitted necks are popular or not at the moment was not my point.just pointing out to B.B.you can get quite close on neck clearance.

Ed

Ed, you're correct that as long as you have any clearance, the bullet will release.

The problem is that for this to work and the gun to shoot well, the case has to fit the chamber perfectly....there can be no excessive sizing done to the shoulder, the back of the case or how much the shoulder is pushed back. If the case is loose or wiggles in the chamber at all and you're running 'fitted neck' type clearances (under .001), one side of the neck will be resting against the chamber neck(unless the bullet is seated firmly into the lands...unlikely in a huntin' rig). When the case fires, the bullet is pushed off center as the case and neck expand to fill the chamber. And a bullet that starts up the barrel crooked will give poor accuracy (even hunting accuracy).

I've worked with a couple of huntin' rigs that had these same issues. In every case, opening up the neck clearance ( going to .008 clearance on one 300WSM) resulted in much improved accuracy.

Just what I've found in my tinkering, FWIW.

Good shootin'. -Al