Is it true about 'fitted necks'?


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Bitswap
January 11, 2008, 10:15 AM
I was surfing over at Varmant Al's site and saw this (http://www.varmintal.com/ahuntold.htm). Since then I researched the concept of 'fitted necks' a bit further and found that it is nothing new.

There is a statement in this article that states: the brass should last indefinatly.

I haven't been able to confirm that statement. Anyone here try this or know if this is true? Is this method worth the effort and costs involved?

Thanks,
Bit

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Walkalong
January 11, 2008, 10:37 AM
With the proper sizer, proper technique, and proper setup, brass will last a long, long, time. Work hardening is what kills brass.

If you are barely sizing the body, (.001 or less), barely bumping the shoulder,( .001 or less), and have .0005 to .0075 neck clearance with a loaded round, it will work.

We do this in Benchrest and shoot "hot" loads, but the fine Lapua brass, using these methods, lasts a long time. When you go through a lot of trouble to prep brass, this is a good thing.

It is not for the new reloader. You cannot just set up your custom cut sizer once and go either. The new soft brass will slowly get harder and springier. If you don't keep up with the measurements and how much you are
bumping the shoulder, and adjust accordingly, it will go wrong. You have to adjust as you go until the brass "settles" in. If you bump it too much you will overstress your brass. If you bump to little, it will get to be to hard to chamber, and you will never get it back right once it is "settled in" at the wrong length. We are talking less than .001 error here.

The good news is you don't have to cut it that fine to get extended brass life, it just won't be as good as if you did. It can still lenghten brass life enough to be worthwhile, along with some accuracy enhancment by getting the bullet lined up with the bore a little better.

Bitswap
January 11, 2008, 10:51 AM
Understood Walkalong.

So, you still have to bump the shoulder a bit for it to work. Too bad the redding competition shellholders only go in 0.002 increments...sure wish they made 'competition' sizer dies with micro adjustments...

So how many reloads would you get from brass processed like this? Would it be any different from 'normal' chambers and neck annealing (about 20 reloads)?

And what fails? Incepient splits or neck splits?

Walkalong
January 11, 2008, 03:03 PM
I really don't know. I don't keep count. My first batch of .222 mag brass finally got so work hardened I tossed it. I got at least 20 fireings from it and could have annealed it again. It had not failed. I was using a Lee Collet die and it had left "creases" in the neck where the split in the collet was because it was so soft from annealing the first time. I just did not like that so I tossed it and changed to a Redding bushing type sizer.

I have shot 6PPC brass probably well over 50 times each before changing. I have not worn it out, the barrel needed changing and so I made a new set for the new chamber, no matter that it was very close to the last chamber.

You should not have any case seperation doing this, if done right. You would eventually see a split neck or body I guess.

You do not have to bump the shoulder much, but you must bump it a tad. Under .001 will work. I try to get it where I can barely measure the difference. I just adjust the lock ring on my sizer a hair at a time, using a special tool to measure the amount of bump. It is a short piece of an old 6MM barrel with the neck and the very first part of the shoulder cut into it. Slip it over your neck and measure from the base to the end of the tool. It rests on the shoulder and will show any difference. Sinclair has similar tools for doing this. they all work. You can use the Stoney Point (http://www.sinclairintl.com/cgi-bin/category.cgi?category=REMTHT&type=store) headspace tool to do this. Or a simple bullet comparetor that has a hole size that will slip over your neck.

Bitswap
January 11, 2008, 10:41 PM
Very good information.

I have the tools to measure and confirm headspace and neck thickness. Add to that some machine skills with a mini lathe and mini mill. Just enough skill to be dangerous (0.001 accuracy).

Anyway, one last question, if I may.

I'm thinking this would not work with drop-open actions. For example, my TC 308's headspace is 1.627 to the breach. After firing a round, the headspace of the fired round is 1.633. That's an increase of 0.006 that I have to bump back. Why it's 0.006 longer is an issue for another thread... It's probably the nature of the action. I guess it could work, but work better in a bolt or lever action.

Thoughts on this?

Bitswap
January 11, 2008, 10:43 PM
double post, sorry

Walkalong
January 11, 2008, 11:01 PM
Don't bump it back .006, bump it back .001 or less. Control headspace with the sizer. All brass should be done this way for long life. Don't just full length size it. Adjust the full length sizer untill the bolt closes easily and no more.

The front half, give or take a bit, expands to seal, fill and grip the chamber and while the back half tends to "slide" and "stretch" back to the bolt head or breechface while the front half is stationary in the chamber, which is where you get the case stretching that causes case head seperation.

USSR
January 11, 2008, 11:11 PM
Guys,

The article is not talking about extending brass life by controlling cartridge headspace. The gist of the article is about having minimal clearance in the neck portion of a tight necked (not SAAMI) chambered rifle. This cannot be done with factory chambers.

Don

Bitswap
January 11, 2008, 11:55 PM
A drop-open action is a little different than bolt or lever actions. I have all three in 308. I can get away with a shoulder bump of 0.001 in the bolt and lever actions since the 'breach' or bolt doesn't move when fired.

If the drop-open TC were rock solid, it should size to 1.627. But because of flex in the system, it will lengthen to 1.633. I did try to bump 0.001 on that 1.633 cartridge and got vertical strings because it was pre-loading the action. When I sized to 0.001 (1.626) to the breach, it was perfect. 1.626 is not full-length sized, but sized to fit the TC.

Anyway, you've answered my questions and I thank you. Think I'll get a barrel made and give it a try.

Bitswap
January 12, 2008, 12:14 AM
Don,

Understood. It's a given this is not a factory chamber, or even a match chamber but much tighter. So tight, in fact, that neck tension is controlled by neck thickness and neck sizing isn't done, per se, but cartridge sizing must be done (very little) to maintain correct headspace.

The shoulder bump we're talking about is nothing new to me. For my fire-formed brass, I do it.... if the action allows it.

It's a given that this will increase accuracy. But, an additional benefit is extended case life. I'm not sure how much space they give for a match chamber, but this appears to be a different concept entirely. Thus the term 'fitted neck' verses 'match chamber'... two totally different concepts.

Walkalong
January 12, 2008, 01:49 AM
A "match" chamber is usually not that much tighter than a standard chamber and does not need "fitted" necks.

A custom "tight necked" chamber is what we are talking about. We are talking about more than what the article included. Just shootin' the S***

My 6PPC chamber has a .262 neck. I ream and turn my brass so a loaded round is right at .2615. Pretty tight.

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