neck turning

L

L.G

Guest
Hey fellas, would someone explain to me why you have to outside neck turn when you have a match grade chamber for example a 300 ultra mag.
 
I cant answer that,I was told I would have to neck turn my brass once I have the gun. If I chose the match chamber.
 
One thing that a gunsmith can do, when doing a barrel job, is to run the chamber reamer into a couple of inch long piece of barrel, far enough that the shoulder angle is cut for most of the width of the shoulder. This will give you a gage that can be very useful. One of the several things it can be used for is to check ammunition for neck clearance. In the mean time, ask for a reamer print. You can scan it and post the scan here. Then we can have a more precise discussion of what may or may not be required. Not all match chambers require neck turning.
 
You want the thickness of the brass the same all the way around the bullet so even pressure is applied all the way around bullet, this usually requires turning the necks of the brass. Different shooters have different thicknesses they think works best some go as thin as .010". Then you have the clearance they like between the case and the chamber, .002", .003" etc. Some run so little clearance they don't even need to resize their brass. They come up with their magic numbers and they have a custom reamer made that gives them the neck diameter they want. To get all this to work, they have to turn the necks. No way you're gonna get those tolerences with factory stuff.

For instance, say a factory 6.5 is .300". The bullet is .264" and depending on whose brass lets say it's .015 (and probably not even all the way around). This gives you and overall bullet neck diameter of .294" that's .006" clearance. Turn the brass to make it even all the way around and it's even more. Not very condusive for benchrest accuracy.

Also beware. The clearances they run in match barrels are not really what you want in a hunting barrel. A bullet that chambers a little snugg ain't so bad on the bench but have one hang on a hunt can ruin a whole trip if you only had a chance for one shot.
 
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LG
You need to add the neck thickness x2???
So lets say that your bullet is
.308 diameter
and the thickness of the brass measures at the thickest point on the neck
.016 then you would
add
.308
+.016
+.016
= .340
If your chamber is cut with a .338 neck diameter then you will need to do a light turn on your neck to get your loaded cartridge neck diameter down to .337 or smaller.

I go for a .002 clearance. So if I was using a 300 RUM with a .338 neck then I would turn the neck so that I get a final diameter with the bullet seated of .336

Ted
 
Basic Facts - Outside neck turning.

The neck of a loaded round must have clearance in the chamber to let the bullet exit freely on firing. If there is a snug fit, zero clearance, the chamber pressure on firing may go way up, maybe more than wanted. The loaded ammo neck diameter of .344" is maximum for a factory chambered rifle. Drawings here http://www.stevespages.com/page8d.htm
 
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Ok,heres the problem now, Ive measured the neck diameter on a loaded round and it is .337 also a piece of brass thats just been sized is measuring .334 and never been fired I dont understand why its so small.what do I do if its way smaller than my match chamber lets say 006.
 
How do you know it is so small?
How do you know the sized neck is to small if you haven't checked the chamber dimensions by measuring a piece of fired brass?
If your chamber neck measures .333 then it isn't to small. It would be to big.

Take the first step first.
Find out what your chamber neck dimensions are!
You are putting the cart ahead of the horse!
 
L.G said:
Hey fellas, would someone explain to me why you have to outside neck turn when you have a match grade chamber for example a 300 ultra mag.
Click to expand...

Whomever led you down this path, be it gunsmith, friend, mentor or advisor, did not adequately educate you on what you were getting into with this chamber.
Your gunsmith should have provided you with a "gizzy", a barrel stub that has the shoulder, neck, freebore and leade in it, made with the chamber reamer. If the gunsmith is building tight-neck chambered rifles, he should know this but just failed to do it.
You now have to learn a lot about chambers, neck turning, and measuring a number of things so that you can use this rifle. You have the right to be upset at someone about this.
There are a lot of "match chambers" made with "match reamers" that do NOT require neck turning.

Opinion by Jay
 
Thanks fellas,know I understand a little better.forgive my Ignorance what got all this started was me wanting a custom set of dies thats raised alot of questions and confusion.
 
NOthing to forgive.
If you are around the Austin TX Area we could get together and I could take you through the steps.
We just want you to get going on the right foot.
 
I would like that,but I live in Tenn. How do you guys feel about the book handloading for competition.
 
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