Last year, I prepped 50 (actually it was more but that's what I ended with)cases to use in shooting factory stock matches. This included neck turning. I did not turn to a specfic thickness but rather had my cutter set to "clean up" about 75% of the neck. I gained what I consider to be a significant increase in accuracy. Those cases were reloaded repeatedly over the course of the summer and fall. Not screamers but loaded toward the top of the chart. This spring I loaded up about 20 of them to try a different load and bullet. Lo and behold, I get a case seperation. About 1/4 in. in front of the web. When I check, ALL fifty of them were definite candidates for seperation. Now over the years, I haven't had but two or three case seperations if that. I get neck splits long before any other part of the case shows wear. Now comes the question part: Could the extra room in the chamber neck cause the case to flow more readidly or what??? I don't know the chamber dims but it was a factory chamber. I don't have a bore scope but using a bore light I could not see any malformation in the chamber. Lastly, I was neck sizing only after the case prep.

Neck turning and case separation are totally unrelated. Look elsewhere for your problem. Case separation usually occurs from repeated full sizing and stretching of the body brass just in front of the web. Something else is causing the separations.

[ 04-15-2003, 23:23: Message edited by: Bob338 ]

338,
Not so, when you are shooting cases that should not have been turned in the first place, for a sloppy factory chamber then expansion from each firing is increased several thousands and that overworks brass and causes fatigue..which is exactly what has happened in this case...

I only outside neck turn one caliber, a 6x45 that has a custom chamber with "0" tolerence and I have to trim the factory expanded 223 brass before it will chamber...

You should trim brass but neck turning, either outside or inside is for extremely tight chambers only...Mostly bench rest guns. Trimming brass for sloppy factory chambers is a receipt for short lived brass and accuracy is probably not better, it was just fired in a fireformed chamber the second go around.....

I doubt the problem is related. I don't know what kind of action you have or what the chamber is nor how hot the loads are. Very hot loads will do things to webs that light loads never will. To some extent at high pressures the rifle and barrel are elastic and will allow a web to move and weaken.

Here the match shooters who score near or at the top turn all necks and weigh each case to 1.0 gr lots.

Your problem is too much headspace from over sizing the body, not neck turning. Every time you fire then size the body down on the case it stretches the body at the seperation ring mainly, causing it to get thinner and thinner there. Neck size and only bump the shoulder back enough to chamber easily when you need to and your problem will amazingly go away.

Turning necks in a factory chamber can give you split necks sooner if you don't anneal, but not seperation. The part of the neck you've changed has nothing to do with what's below it as far as seperation and stretching downd below is concerned.

Ray, the "0" tolerance neck of your, does it have no clearance at all, and do you think that's safe?

It certainly gives one the impression zero tolerance is safe. Even fitted neck chambers are turned to have clearence of a few ten thous. They rely on the springback quality in the brass and aren't needed to be sized back down, just deprimed, primed and then loaded again. Tight neck chambers are usually in the order of .0015" - .002" clearance and still need to be sized to retain the bullet, they both work the brass a hell of a lot less than a factory chambers .005" - .010" normal total clearance. FL sizing is the enemy that leads to case head seperation. Set your FL die so it runs down just low enough to bump the shoulder back enough to close the bolt again and you now have a close to zero headspace FL sized case, this will force the shoulder tight and line up the bullet with the bore as well as neck sizing only...if you do it right. You still are working the brass on sizing, just not as much as stretching it upon firing as it grips the chamber wall as the head it punched back against the bolt where it stops. The amount you trim is closely corralated with how much the seperation ring is being stretched. If you trim less, the brass isn't moving much. Reduce the two factors that cause it and walla!

Brent,
Sorry if I mislead, 0 tolerance chamber means less than .001 in my benchrest and varmint circles. I assumed the same applied everywhere. I will try to remember that in the future.

I have a special set of hand reloading dies for this 6x45 and it does not even require a hammer but a light hammer makes it easier for sure...

I recently shot a 10 shot .285 group with it at 100 yds..It is a Sako L-461 with a custom stock, 20" Douglas barrel, M-70 Safty by Barnes, and weighs a heaping 5 lbs..The late Tony Barnes did the metal work, and I made the stock....My walk around varmint gun..It is quite a gun....

I do not have an explanation, but beemanbeme says separation occurs only on the cases neckturned. There seems to be a relation.

First, the head space seems not to be o.k., maybe because cutting too much into the shoulder area.

I see two situations where dynamics of the alteration of the neck may be causing the case separation

a) firing the catridge
The thinner walls of the neck will sooner (at a lower pressure) and wider open with the expanding gases allowing a higher gas rate to escape before the bullet seals the bore.
I can not imagine how this influences the expansion of the bullet or the gas flow between case and chamber walls. Is there blackening (sooting) of the case different to ones not neck turned ?

b) sizing and seating of the case
With the reduced neck diameter, one may need a smaller bushing diameter.
There have been forces applied through the wide neck to the case body forming it in a way it worked perfectly with. Now these forces have no more "grip" and the case if formed minutely different.
Is the "feel" when sizing, seating, chambering different to the cases/cartridges not neck turned ?

Well, as said, I do not have any explanation or advice...

[ 04-28-2003, 16:32: Message edited by: waitaminit ]

Cutting into the shoulder area. waitaminit has nailed this one.

I would agree with Ray I have seen the some thing when you do neck turning on cases that do not need it. All this will do is weaken the case. If you do not have a tight chamiber you should not neck turn in or out

I would never neck turn a case unless I have to. "Have to" means that you can not slip a bullet into the neck of a fired case (not enough neck clearance)....

And I've (had to) neck turn several hundred cases. It is no fun.

Bottom line, neck turning can have NO relationship to case head separation. Don't care what the relation may "seem".

Cutting into the shoulder in neck turning again can cause no case head separation. The cut you make into the shoulder is far removed from the datum line mid shoulder and in a neck sized case there is no place for the body to stretch enough to cause fatigue at the bottom of the case.
Split necks, yes. Head separation, NO. There is no slop in the case body to enable stretching. Anyone disagrees, please explain how YOU think it can occur.

New cases, long factory headspace, cutting into the shoulder, case shoulder meets datum line upon firing, case head separation. Just my guess.

the cases were neck sized only after fire forming to my chamber. As a sidebar: Can't see how cutting into the case shoulder could case case seperation in front of the web???

[ 04-29-2003, 02:45: Message edited by: beemanbeme ]

I agree with Bob338 completely, well said.

Beeman,
how many firings on those cases there?

If the necks are sooting up badly... they just need to be anealed! No matter how thin you turn em they'll seal up... "if" they haven't work hardened yet.

Ray,
.285" group... 10 shots... 5# rifle, damn that's what we love to hear! What bullet does that thing like the best?

If we are speculating on the cause of the separations, I'll guess, although the original question only asked the relationship to neck turning.

In most chambers, and particularly factory, there is considerable slop. The initial fireforming will stretch the case body from a minimum of about .004" to as much as .008"-.009" in unbelted cases, and as much as .024" in belted ones. (In belted cases, the least stretch I've ever seen is about .015" initially.) Even mostly neck sizing after initial forming the shoulders must be set back after a few reloads. Depending on the number or reloads, even minor stretching near the web can induce the separation following a few of those set backs. Particularly so if there are a couple of FL resizings in the process. The number of reloads isn't given but if they number nearer 20, even that small amount of stretching after bumping the shoulders back, or FL sizing, could induce the separation if the brass was pretty hard to begin with.

I've NEVER had an unbelted case separate in almost 50 years of reloading. I've had some cases I've had to dump becaue of expanded pockets with around 40 reloads or more, not splits nor separations. These were in '06, which is essentially the same case as in this incident. I anneal necks at 4 or 5 reloads in all cases so neck splits are seldom a problem.

My best guess is hard brass, big initial stretch, maybe a shoulder set back or two that was a bit agressive. NOTHING to do with neck turning.

Agree with other responders. No connection with neck turning. Case fatigue from overworking will eat cases pretty quickly. Recently have had some problems with head separations/fatigue my new Rem 700P with an oversized chamber. The gun is within "specs" but overworks the brass to the point you can see a distortion near the base; the cases lasted for 2 firings.

You can try partial full length sizing the brass. That is, back off the full length die of a few thousands. This puts some tension on the neck but does not over-work the brass. This only seems to work on certain dies that still keep the case captured enough to prevent concentricity problems.

Ron

beemanbeme,

What's the gun and what's the caliber?