cartridge case

[kbstenberg]

How much difference in case length do you allow in your reloads. Do you only let there be 2 or 3 thousands of a difference in any batch of ammo. Or do you mix any case length as long as they chamber. Kevin

[Artful]

you talking rifle or pistol brass?

for Semi-Auto pistol I just trim once and don't worry about it again - they never grow.
for revolvers or rifle cases I trim and keep together and load and shoot as a group and
check now and again to see if needs trimming.

[35 shooter]

I'm ticky about that. I want revolver and rifle all trimmed same length. There are better and worse trimmers out there but most will keep them within a thousandth if set right. I was amazed using a lee hand trimmer on my 35 whelen brass as it kept everything within +1/2 thousandth. I prefer them perfect but thats pretty darn good for a dirt cheap trimmer. For me it's about doing everything i can to enhance accurracy.

[kbstenberg]

Sorry. I was thinking rifle/ bottle neck cases

[41 mag fan]

I keep mine in batches and and keep shooting the same ones, till they hit almost max specs or become hard to close the bolt on, then will trim them all back to minimum and start over

[Lead Fred]

zero

I make them all the same, if they fall short and can be fired to bring them to SAMMI spec, I do.
If not I cut them down and make 308 cases out of them.

[Animal]

According to Lyman 49th ed. they say to discard all brass after they have been trimmed 4 times. Anyone care to chime in on this 'requirement'? and why you choose to follow or not follow this? I'm not sure that this is inline or not with the OPs question, but I see this as an important step when choosing which brass to trash.

[frnkeore]

I believe the reason for that, is because that after the brass has moved that much forward, the web at the case head MAY have thinned enough to start case seperation.

Frank

[35 shooter]

According to Lyman 49th ed. they say to discard all brass after they have been trimmed 4 times. Anyone care to chime in on this 'requirement'? and why you choose to follow or not follow this? I'm not sure that this is inline or not with the OPs question, but I see this as an important step when choosing which brass to trash.

On rifle brass i watch the web area each time i fire them for a BRIGHT ring around the circumference. On max loads it usually shows up in about ten fireings but depending on the load can be many more fireings, especially with cast boolits. Jacketed generally give the shortest case life for me. I trim every time i fire them. When the ring appears it's time to junk them as that is the sign the brass has gotten very thin in that area as the brass has flowed forward toward the neck on each firing. I have cases for my whelen that have been fired well in excess of 20 times
but that is with cast boolits and no faster than 2500 fps. That ring is beginning to show itself on some of those cases.

The ring i'm talking about will be much brighter than the resizing marks on the case.

[Artful]

Take a paperclip straighten it out - make a short leg and reach inside the case you can feel the stretched area on the case - bright ring or no if it gets too deep prepare for head separation.

[EDG]

Most chambers are .020 to .040 longer than your brass. Unless you are crimping with a roll crimp die controlling case length to plus or minus .001 or .002 is totally meaningless.

[EDG]

I think this is a silly statement by Lyman. Brass that is correctly sized for use in a front locking bolt gun is almost immortal. Meaning it will last more than 50 loading cycles. When it does fail it is usually due to a split not a case head separation.


According to Lyman 49th ed. they say to discard all brass after they have been trimmed 4 times. Anyone care to chime in on this 'requirement'? and why you choose to follow or not follow this? I'm not sure that this is inline or not with the OPs question, but I see this as an important step when choosing which brass to trash.

[Animal]

EDG, what I am trying to understand about this is Lymans claim that the case wall will thicken as it stretches. This might be old news for some of you, but I'm trying to wrap my mind around this. Somehow the mouth of the case will increase in wall thickness as brass from the head moves toward the mouth during firing. When this condition happens it can cause a projectile to seat tighter in the throat or chamber, thus increasing pressures.

My thinking leads me to believe that nothing gets thicker. Case walls stretch as material pulls away from the head, causing weaker walls, not thick walls.

Has anyone experienced this? Do walls get thicker in real world applications?

[Carolina Cast Bullets]

There is something else to consider and that is "work hardening". This happens
when the brass is stretched and sized back down, specially in the neck area.
When that happens, most often in heavier loads, the brass in the neck area hardens
as it is being stretched and sized back down, most often leading to neck splits. The
more you work your brass, the faster it happens. Thats why lighter loads are much
easier on your brass, your firearm and your shoulder. If you need an illustration, take
a wire coat hanger, bend it and keep bending it back and forth. It quickly breaks. That
is "work hardening."

Jerry
Carolina Cast Bullets

[MarkP]

EDG, what I am trying to understand about this is Lymans claim that the case wall will thicken as it stretches. This might be old news for some of you, but I'm trying to wrap my mind around this. Somehow the mouth of the case will increase in wall thickness as brass from the head moves toward the mouth during firing. When this condition happens it can cause a projectile to seat tighter in the throat or chamber, thus increasing pressures.

My thinking leads me to believe that nothing gets thicker. Case walls stretch as material pulls away from the head, causing weaker walls, not thick walls.

Has anyone experienced this? Do walls get thicker in real world applications?

It flows forward --- thinning the wall by the head and thickening the wall at the mouth.

I have noticed this with my hotter varmint rounds. 22-6mm, 6-284, 257 Wby Mag,

[Animal]

Ok, this is making more sense when considering the heat applied from hot loads.

[9.3X62AL]

EDG, what I am trying to understand about this is Lymans claim that the case wall will thicken as it stretches. This might be old news for some of you, but I'm trying to wrap my mind around this. Somehow the mouth of the case will increase in wall thickness as brass from the head moves toward the mouth during firing. When this condition happens it can cause a projectile to seat tighter in the throat or chamber, thus increasing pressures.



My thinking leads me to believe that nothing gets thicker. Case walls stretch as material pulls away from the head, causing weaker walls, not thick walls.

Has anyone experienced this? Do walls get thicker in real world applications?

I have seen cases that lengthened upon firing on many occasions. Thickening of case necks? Might be possible, given that brass is migrating forward as evidenced by the case's lengthening as above. I have only seen this in the 22-250 using J-words at top end velocities, two rifles showed this trait. I addressed it with neck reaming.

The case lengthening is largely halted once the case shoulder has a closer fit to the chamber's shoulder, in my experience. I agree with EDG that my cases usually expire from neck cracking and not from incipient or actual head seperations, likely due to close headspace control at the case/chamber shoulder in my neck-and-shoulder calibers. In rimmed revolver or rimless/semi-rimmed pistol cases, there has been little or no lengthening once they have been fired once and trimmed. Expansion within the chamber actually seems to shorten them slightly, and resizing & expanding tends to return the cases to their former trimmed length, usually within .0003"-.0005" one way or the other. As a lot, they retain their length pretty closely.

[country gent]

My brother had a ruger 77 in 220 swift that the original 200 norma cases necks thickened to the point they wouldnt accept a bullet into a fired case anymore. Starting loads gave excessive pressure when he brought everything to me to figure out was happening. Under the pressures of firing most modern rifle rounds brass can and does move shift. Measure a case neck Load and fire this case for 10-15 cycles and remeasure the neck depending on caliber pressures it will ahve thickened some. Brass flow from the case head to the neck shoulder under firing it has to go somewhere.

[Animal]

Great explanation and examples of concepts covered in my manual.

[M-Tecs]

Neck thickening will happen with most high intensity bottleneck cartridges irrespective of any brass flow from the case head. The material in the shoulder flows forward into the neck. This will happen with neck sized fire formed to the chamber brass that shows no sign of web thinning. If you section a case you can measure the thinning of the shoulder on neck sized only brass. Normally it's not a problem. The only place I see it is on my 6mm BR brass with a bunch of loading. Most of my other cases are lost due to primer pockets loosing.

Over doing full length resizing of the brass does increase the rate of thickening but I believe the brass that is thickening the neck is coming from the shoulder and not the head. When the brass is sized to the point headspace becomes an issue when the firearm is fired the front portion of the case adheres to the chambers walls and doesn't flow. The head being thicker doesn't adhere to the chamber and is pushed back. That is where the separation ring forms.

When the case is sized again the area in the separation ring doesn't compress so this forces the thicker material in the shoulder to be sized into the neck. The thickening of the neck is because the front 3/4 of the case is moving forward and since the case walls are tapered the thicker material in the shoulder gets sized into the neck.