Case Head Separation vs. Resizing Ring

olsenjb

I've posted this question under "Ask the Experts", but I thought I'd post it here as well.

I'm new to reloading and I'm very nervous about telling the difference between the bright ring that appears indicating brass thinning and case head separation vs. the bright ring that is formed from resizing the brass. I was wondering if anyone has any photos comparing the two, or any other sure-fire ways to tell the difference? I have some 1x fired factory brass that I've resized and they have a thin bright ring near the head. It has me very nervous. Thanks for your help.

JustC

http://forums.gunbroker.com/topic.asp?TOPIC_ID=143341&SearchTerms=casehead

olsenjb

JustC...Yeah, I came across that post, but I'm not really seeing the bright ring from resizing. How does it compare to the ring on the 2nd case from the right? Thanks for your help.

Tailgunner1954

A pre-seperation ring will be a hair width wide on the outside (seriously it will look like the narrowest of pencil lines), it's a "V" shaped notching on the inside. You can make a "L" shaped tool out of a paper clip to feel for the presence of the "V" on the inside of the case.
When in doubt use a fine tooth hacksaw to section a case open for a visual understanding of what's going on inside.
BTW, keeping the amount of body sizing to a minimum will increase the case life before seperation occures (esp on belted and rimmed cases).

JustC

That shiny ring is after firing in the rifle. The body has NOT been re-sized but the shiny ring is evident. That will indicate the impending seperation. The die body tends to leave the mark on the case a bit lower than the seperation ring will appear at.

nononsense

Here are some illustrations for the discussion:

olsenjb

JustC...Forgive my ignorance, but you're saying that the body on the 2nd case from the right has never been resized, but you're still getting case head separation? I thought that case head separation became a concern only after several full-length resizes/trimming that thinned the case. Am I wrong?

JustC

no, what I was trying to say was that the particular cases in the picture (I assume you mean the 6.5x55 cases?) have never been sized. These were fired 1x in an overly headspaced chamber (military rifle) they were brand new ammo. You see the shiny ring showing the impending seperation and can also see one that cracked enough to more clearly point at the fact that danger is near. If you were referring to the pistol case that is seprated, that was from too many FL sizings and firings.

Continual FL sizing and compressing of the expansion ring, coupled with brass growth during firing will no doubt speed up casehead seperations, but excessive headspace can as well.

olsenjb

Yeah, I was referring to the 6.5x55 case with the bright ring, but had not split yet. I didn't realize such a thing would happen in brand-new brass simply due to excessive headspace. Is a long chamber often a problem in newer bolt-action rifles (in particular, I recently purchased a Rem 700 VS-SF in 22-250 that I'm reloading for) or mainly just a problem in older military rifles?

Also, my Speer manual states that factory dies are made such that they will never push the shoulder back beyond factory standards when resizing. Is this true, or is it better to partially full-length resize just to be safe?

JustC

The excess headspace "should not" be an issue in your new production rifles (great choice by the way, I have the VSSF in 220 swift) it is the older military rifles or those chambered incorrectly. Newer rifles are pretty tight, not match tight or min spec tight, but better than a few decades ago.

The dies may not overly push the shoulder according to some hard and fast rule or measurement, but the fact remains, every chamber is an entity unto itself and must be measured accordingly. I have begun experimenting with PFL sizing versus NK sizing and have been pleased thus far. It does seem to cut down in groups some, but I have been trying this in a rifle I have that is somewhat stubborn when it comes to grouping well. I beleive the PFL will benefit you on paper.

Things you need to really get this down:
stoney point headspace guage kit
calipers

using the headspace guage set on the datum line on the case shoulder, you incrementally set the FL die down very little at a time from about 1 nickels thickness away from the shellholder. You measure the case-head to datum line, and bump the die down very little at a time until the shoulder is pulled forward by maybe .002" (measurement increases by .002"). This will partially size the body and expansion ring to provide easier chambering, but also when pulling the shoulder forward, gives the compressed fit of case and chamber. This aligns the bullet with the bore more uniformly as it is "held in compression" and not allowed to sit on the chamber bottom due to it's being fully resized and having it's shoulder pushed back, making for very little or no compression.

the less you work the brass, the longer it lasts.

olsenjb

Thanks for the info JustC. I really like the rifle and it has really treated me well with the factory ammo I've ran through it.

Perhaps I should mention that I'm not that concerned about shooting the smallest groups on paper, shooting match, etc. I'm really just trying to reload in a manner that is safe, will allow for the longest brass life and will be used for hunting nearly exclusively.

Someone mentioned in a post previously that they soot the neck/shoulder of their brass with a flame. Then, they slowly adjust the FL die down until it just hits the shoulder. Is this a sufficient way to set up for partial full length sizing safely without buying the additional special equipment like the headspace gauge kit? I realize it might not be as accurate, but that really isn't my main concern as long as it is safe and will shoot relatively accurately.

JustC

You can do it that way. The shoulder just being touched will not be pulled forward, so you have basically sized the neck and very little of the body. You should have sized the expansion ring enough to allow smooth chambering. Once you notice the shoulder being touched by the die body, then maybe 1/32 more of a turn should give you a slight shoulder compression or at least tighten it up some. I am a big fan of making them match your chamber dimensions, and this is one way to do that. You will be safe even with FL sizing, you will just have to watch for case-head seperation signs when FL sizing every time. The PFL will make for a much longer life span, and if the caliber is a higher pressure chambering, the primer pocket will be gone before the case-head seperates.

Just monitor the case length as it is sized and fired. If you are getting a lot of case lengthening, you may wish to go to PFL to help slow that down a bit.

olsenjb

Thanks...Yeah, as I recall, I think that poster mentioned that once the die is just touching the shoulder based on the soot being smeared, then to tighten the die down just a little more and lock it in place.

Am I correct in thinking that you have to trim cases the least often with neck sizing, then PFL, and finally you have to trim most often with FL sizing?

JustC

that would be my conclusion as to trimming. The calibers with a lot more body taper (257rbts, 220swift, 300H&H etc) will grow more due to the brass flowing more easily down the taper and across the shallow shoulder angles. The sharper the shoulder and flatter the body, the less the case will grow each firing, this is one of the great benefits of the "Ackley Improved" conversions with their non-tapered body and 40* shoulder angles.

Studebaker Hawk

If the calibre in question is a 6.5X55, there is something else to know -domestic brass is undersized by .006" in the head area. This is not so with imported 6.5X55 cases. This can and will cause problems in a modern bolt gun when pressures are turned up.