Neck Clearance

L

Lucky Shooter A

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I've chambered a barrel with a 222 reamer with a specified neck diameter of .248" .

The case necks have been turned to .011" wall thickness and the loaded round necks measure slightly over .246" .

My best efforts to measure the reamer neck show about .2485"----so it appears the loaded neck clearance is about .001" per side.

I've found that a bullet can't be slid by hand into a fired case.

I've never experienced this before and wonder if its a problem.

Its not a big deal to turn more off the case necks to get more more neck clearance.

What makes sense here?

Thanks.

A. Weldy
 
That's common with a tightly fitted neck. I prefer a little more clearance than .001". I shoot for .002" total clearance. If you look at the carbon ring around the outside of the neck. If the ring is a straight line going around the neck then it doesn't have as much clearance as I'd prefer. If the ring dips down on one side, that's what I want as to clearance. It's not uncommon though for a reamer to cut slightly oversize all depending upon how well the operator has everything on center when cutting the chamber. It would be nice to know the exact neck diameter of the chamber. But, I doubt if that's very necessary. It still comes down to if it shoots well on paper with no excess pressure signs you're good to go.
 
I've found that on the first, and sometimes second, firing of new brass I can't slide a bullet in the fired case. After that, it just barely goes in. This is with Lapua .222 brass turned to .0105 in a .247 neck chamber.

Also, as Mike noted, I have a straight carbon ring on those first firings. After successive firings I now have the wavy, two dips carbon pattern. I think I read in Tony B's book that these dips coincide with the lugs on the bolt.

Jerry
 
Thanks for replies

This setup appears to be safe. I've ramped up my load to 20.7 gr IMR 4198 with no excessive pressure signs.

I'll try this neck thickness for a while before turning any more off.

Mike, I'm not likely to get any extra slop from my reaming----thanks to all the good advice from this board. After indicating the muzzle and throat, the barrel was drilled and pre-bored and a Bryant type floating pusher was used. There is no play when the reamer is put back in the chamber.

Jerry, it appears we have about the same loaded round clearance. I'm starting with some used Rem and Hornady brass and will later switch over to some unfired Lapua.

Thanks to both of you for the help----this is my first experience with such tight neck clearance.

A. Weldy
 
Lucky Shooter A said:
I've chambered a barrel with a 222 reamer with a specified neck diameter of .248" .

The case necks have been turned to .011" wall thickness and the loaded round necks measure slightly over .246" .

My best efforts to measure the reamer neck show about .2485"----so it appears the loaded neck clearance is about .001" per side.

I've found that a bullet can't be slid by hand into a fired case.

I've never experienced this before and wonder if its a problem.

Its not a big deal to turn more off the case necks to get more more neck clearance.

What makes sense here?



A. Weldy
Click to expand...

Your best efforts to measure the reamer were probably real close to actual dimensions. Every reamer maker I have ever delt with works with a plus .0005 minus zero tolerance.
 
Over the years I have tested neck clearance several times from several calibers (6PPC, 6BR, 6Dasher, 243, 243-AI, 300-WSM, 300-WM), and have never seen accuracy gained or loss to having tight clearances (tight neck). Convincingly enough that I run ample clearance (.003" or more) to eliminate some risks, in everything.

My 2-Cents
Donovan
 
Thanks Jay and Donovan

I've thought clearance is clearance----as long as its guaranteed-----but didn't know.

I'll shoot these cases some more as is before turning any more off.

Thanks again for the help.

A. Wedly
 
Just a suggestion

If you like to shoot lots of different bullets it is a good idea to mic the bullet, record and then seat in a turned case and mic once again at the pressure ring, record. I continually check this just to make me happy. :)
Centerfire
 
Lucky Shooter A said:
I've thought clearance is clearance----as long as its guaranteed-----but didn't know.

I'll shoot these cases some more as is before turning any more off.

Thanks again for the help.

A. Wedly
Click to expand...

Keep in mind that neck clearance and neck tension can be related in picking the neck sizing bushing and how heck tension changes with the same bushing over many firings of the same brass and some powders do react differently to varying neck tension.
 
Centerfire and Jerry

I've considered all this but am not sure just what to expect as I fire these cases more.

I have .243" and .244" bushings and will start there and see how the cases hold up.

Boyd Allen is trying to get me to use a FL die without the expander----even if I have to turn the necks more. Might try a few of these to see how straight
the cases will be.

Thanks for your suggestions.

A. Weldy
 
When you run a close neck clearance, everything is OK if you watch out for dirty cases, and more importantly, changing bullets. A close neck doesn't shoot better but does reduce some effort otherwise. If you're not taking advantage of that reduction, loading as you would sans the close neck, then I would recommend cutting your next set of necks a bit thinner. Again, there's nothing wrong at all with case necks that have just a skosh of clearance as long as the skosh remains.
 
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