Neck Separation

[shelpster66]

Posted this at SC so I wanted to post it here too.....

I have been shooting these Win 308 brass for close to 8 reloads on these cases alone. I have started neck turning them about 4 reloads ago and haven't had any issues. The other day at the range I went to chamber a round and it would not go....gave it another push....no dice. I typically look at each and every piece of brass the ejects and inspect it for pressure signs etc....apparently I didn't inspect the last case and wasn't looking close enough at the necks.
The last shot separated the neck from the shoulder and left it in the rifle. This is why the other round would not chamber.
At that point I was done shooting because I wasn't sure where is was and how bad it was stuck. Packed up my stuff and went home.
Upon arriving home, I took out the rifle and the range flag and the neck had come out on the flag and wasn't stuck.....

The round that separated...

You can see where it has perforated the case neck here....

A round that has been neck turned ...notice where I stopped....

These are the rounds that I loaded and neck turned.....it doesn't look as though I have went down too far......or did I????

So am I doing anything wrong here? Is it just the life of the case has met its end? I am trimming the case necks to 11.5-12.5 (0.0115 - 0.0125)....it varies....maybe I'm going too close to the shoulder and as it expands it gets thinner and then the pressure just kills it..... I full length re-size btw....42.5gr of varget.

Would love to hear some opinions and thoughts...I would think the brass should last longer that 8 or 9 reloads...

thanks,
Mike

 

[former naval person]

Re: Neck Separation

Probably a combination of things. Eight reloads without annealing means a lot of work hardening. That makes the brass brittle. I see you have significantly thinned the neck. I understand that the real shooters will turn the necks just enough to clean up @90% of the neck rather than cutting as deep as you have. Did you have to cut that deep in order to have neck clearance in the chamber? Basically you have created a "stress riser" in the neck at the point you have ended your turning procedure. I'd anneal them now and keep an eye on them. If it happens a few more times I'd can the brass and start afresh. JMHO

 

[oldfatguy]

Re: Neck Separation

Looks like you've identified the problem: turning the necks too far down into the shoulder. I turn my case necks but always stay far enough up to avoid leaving a "step" at the shoulder.

Good job on the pictures.

OFG

 

[Deadshot2]

Re: Neck Separation

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oldfatguy</div><div class="ubbcode-body">Looks like you've identified the problem: turning the necks too far down into the shoulder. I turn my case necks but always stay far enough up to avoid leaving a "step" at the shoulder.

Good job on the pictures.

OFG </div></div>

Too far into the shoulder might cause this but then he'd be missing some of the shoulder.

By not going all the way to the shoulder there was a step created and the case merely "sheared" off at this point. The fat part of the shoulder stopped when it hit the wall of the chamber and the "thin" part kept moving. Wouldn't take many firings for this to happen in the best of circumstances.

If one wants to retain some "thickness" to help center the case in the chamber, it's better to only partially neck size (about 75% of the neck length). This leaves an external "doughnut" that will center the case. Since the case neck is all the same thickness with this method no "shearing" action takes place.

A good die to do this with is the Forster Neck Size/Shoulder Bump bushing die. It allows for an adjustable sizing length for the neck and it also bumps the shoulder back a couple thou's so the case will chamber easily.

 

[shelpster66]

Re: Neck Separation

Thanks for the replies....
I kinda figured that's what I was doing wrong......you can see in the last picture where the color of the brass changes before it meets the shoulder .....that is where it cuts most of the brass after resizing. It only skims over the rest of the neck. I took note of it because it did it the last two times. Didn't think too much of it until this happened.

I'll adjust the depth to bring it back a little and try to stay away from the neck as much as I can. I neck size to be sure the neck (outside) is as concentric as possible.

I use an RCBS set to resize and I've never really had a problem. What would the Forster Neck sizer do differently than what the RCBS is doing now?? Other than the obvious lack of full length re-size....

I really would like to get this figured out....funny that the shot that popped that neck actually hit the gong at 565yds. Didn't even feel any different than the others. what are the safety implications with this if it happens again?

Thanks again for chiming in!

Mike

 

[BuzzBoss915]

Re: Neck Separation

Why did you decide to turn those necks after 4 reloads? Do you know the dimensions of your chamber in the area of the neck? If this is a factory chamber, I might have done a partial clean up with virgin brass or after the first fireforming load, as there seems to be some disagreement on that issue?

It looks like you trimmed too much without consideration of your chamber dimension. There was several firings and expandings and resizings and, (in my opinion) they all are going to separate at some point in time and they might not come out so easily. It's a bad situation so I would toss the brass and start over....with just a partial neck clean up on new (edit: resized) brass. BB

 

[shelpster66]

Re: Neck Separation

BuzzBoss......I have not measured the chamber area where the neck would be. I was having issues with the round not chambering without having to "push" it in harder that I thought necessary. Turning the necks alleviated some of this, but also realized that it may be the shoulder as well. I measured the K&M neck turner to cut down to right above the shoulder figuring this would help it sit better in the chamber......it did, but now I see that it's too close and is cutting into a thin part of the brass.

I agree with you...after firing several times, resizing, and neck trimming, I may have to toss these. I neck turn every time to be consistent with my brass, but will have to reduce the times I turn the necks.

The process-
4 hours in the tumbler
F/L re-size (de-prime)
Forster trimmer to 2.005
Neck expander
Neck turn to 0.0115-0.0125
Steel wool clean up (still on drill)
Primer pocket clean
= clean, exactly the same every time, shiny brass

 

[ChrisGarrett]

Re: Neck Separation

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BuzzBoss915</div><div class="ubbcode-body">Why did you decide to turn those necks after 4 reloads? Do you know the dimensions of your chamber in the area of the neck? If this is a factory chamber, I might have done a partial clean up with virgin brass or after the first fireforming load, as there seems to be some disagreement on that issue?

It looks like you trimmed too much without consideration of your chamber dimension. There was several firings and expandings and resizings and, (in my opinion) they all are going to separate at some point in time and they might not come out so easily. It's a bad situation so I would toss the brass and start over....with just a partial neck clean up on new (edit: resized) brass. BB </div></div>

Yeah, if it's a factory chamber blowing out the necks to ~.345" already, the work hardening that's going on via neck sizing and after neck turning would be enough to weaken any metal, let alone some brass necks with ~8 cycles on them.

Metal fatigue.

Chris

 

[BuzzBoss915]

Re: Neck Separation

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> BuzzBoss......I have not measured the chamber area where the neck would be. I was having issues with the round not chambering without having to "push" it in harder that I thought necessary. </div></div>

It seems to me that it is more likely you are not bumping the shoulder enough? It's rare that either a full length or neck die would not resize the <span style="text-decoration: underline">neck</span> enough so that the reloaded round will chamber. I would look into how you approach the resizing operation and specifically, how you adjust the die.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> I neck turn every time to be consistent </div></div>

I think this is a mistake. There is no justification for turning necks more than once, MAYBE twice, initially. After that, you are doing more harm than good. BB

 

[my human host]

Re: Neck Separation

How often necks need to be turned will depend on many things. Shoulder angle of the case being a big factor. When necks thicken due to brass flow they rarely do it in a concentric fashion. Just my 2 cents.

 

[shelpster66]

Re: Neck Separation

As the brass flows forward, my thought is it would flow towards the shoulder/neck, that is why I kept the neck turning as part of the process. I didn't realize that the top of the shoulder was going to thin and thus be the weak point as I continued to turn it.

My best guess is now I need to neck turn once, F/L re-size once, and then bump the shoulder and neck size going forward....until it gets too tight to chamber without effort....then run through the process I have above.

Does that make sense? I agree what I'm doing now isn't going to prolong the life of my brass and could lead to other problems going forward.

thanks,
Mike

 

[BuzzBoss915]

Re: Neck Separation

I think so? Sometimes, focus (on) one thing can really cause a misdirection. In this case, I think over enthusiastic neck turning is a problem.

As far as the previous comment that many factors decide how often to turn necks, in my opinion, those "many things" appear to be a bit murky from this angle. You want consistent neck tension but not so much that you are working the brass needlessly. I don't know? I'm for <span style="font-style: italic">first, do no harm</span> and you better be sure when you are removing material that you are going the right way because you can't put it back. BB

edit to correct spelling, please excuse!

 

[my human host]

Re: Neck Separation

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BuzzBoss915</div><div class="ubbcode-body">I think so? Sometimes, focus one one thing can really cause a misdirection. In this case, I think over enthusiastic neck turning is a problem.

As far as the previous comment that many factors decide how often to turn necks, in my opinion, those "many things" appear to be a bit murky from this angle. You want consistent neck tension but not so much that you are working the brass needlessly. I don't know? I'm for <span style="font-style: italic">first, do no harm</span> and you better be sure when you are removing material that you are going the right way because you can't put it back. BB </div></div>

High pressure causes brass flow.

Constant full length sizing can do the same.

I would think that softer brass would flow easier under pressure, but that is more theory than fact.

As far as the shoulder angle having an effect on brass flow, that is pretty much beyond debate. I've reloaded for many different Ackley Improved rounds. Ask anyone who's run an AI whatever and they'll tell you trimming is rarely necessary. That is due to reduced brass flow when compared to the parent case.

Not trying to start a pissing match. Just clarifying my statement.

 

[BuzzBoss915]

Re: Neck Separation

Yeah, I know. I own six Ackleys. They never need trimming.

I only turn necks for tight neck chambers and only do it once. I don't care much what others do but I know what works for me. BB

 

[Deadshot2]

Re: Neck Separation

Consider a new neck turning tool that has the cutter cut to the proper angle for cutting into the shoulder. Many of the new cutters for .308 have the leading edge of the cutting tool ground to a 20 Degree angle (angle varies by caliber)and the makers recommend that you actually turn the neck to the point where you are cutting on the face of the shoulder. This thins the shoulder a slight amount and reduces flow of metal into the neck which can cause doughnuts to form inside the neck.

I just modified my cutter bit myself and it does a wonderful job of turning the neck, forming a slight radius at the neck/shoulder junction, and removes a slight band of metal from the shoulder about 3/16" wide.

This seems to be the norm now when I look other's brass at the range.

 

[shelpster66]

Re: Neck Separation

Makes sense.....I think what I'll do first is back off the depth of the pilot and stay further back from the shoulder. See how that works for me. I have the K&M trimmer and it seems to be a good quality piece of equipment. But, if I'm going too far down the neck, that's my fault. Going to borrow another set of dies from a buddy that has the shoulder/neck resizer and see if that helps.
Also need to keep an eye on the other rounds that I haven't shot yet from this batch.....only about 25 left. Will be inspecting them VERY closely going forward.

Thanks everyone for the information and opinions. Should help me figure out my next move.

Mike

 

[rcamuglia]

Re: Neck Separation

My take on it is that he has turned the necks WAY TOO THIN. You can see a huge "step" up in OD before the neck/shoulder junction.

When neck turning, you MUST turn them all the way to the shoulder. This is how you avoid "The Dreaded Doughnut" at the shoulder/neck junction (a doughnut or decrease in the ID)

The brass should be fully resized and expanded with an expander mandrel, the cutter on the turner should be set to BARELY clean up the outside of the case neck. It should clean up the neck maybe 90% and just take off the high spots.

This may help: http://www.varmintal.com/arelo.htm#Neck_Turning

 

[MitchAlsup]

Re: Neck Separation

A) Necks cut too thin
B) sharp edge at the end of the cut--what you want is a nice round transition.
C) you should adjust the cutter so that at least 10% of the original neck is left uncut.

D) I have a set of cases with 30+ reload cycles on them that have never been annealed. 308 Win cases with 47.8 gr Varget--so its not a pussy-footing load. But, to be fair, the necks are bushing resized.