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Neck Tension Changing Over Time

JD Tactical

Private
Minuteman
Jun 5, 2020
10
1
Hey guys, new member here but not at all new to the sport. I thought I would share some interesting info that I learned in the last year. Apologies if this has been discussed before.

While working up a new load last year for my 300 RUM I noticed that my "fresh" loads (loaded within a day or two of shooting) had a considerably higher MV than loads that had sat for about two weeks or so. I am full length sizing all my brass the same way with a redding bushing die and the expander mandrel installed. All loads were the exact same specs but the fresh loads were around 3135 FPS with an ES of around 20 FPS and the 'seasoned' loads shoot around 3075 FPS with the same ES.

I know that a lot of benchrest shooters load and shoot immediately, even loading at their vehicle before the match. As a hunter I can't really do this so now I prefer to 'season' my loads for a couple weeks before shooting.

To back this up, a buddy of mine I shoot with noticed the exact same thing on his 6.5 CM while we were shooting together.

Simply put, I believe brass will 'stress relieve' over time which results in slightly less neck tension. This, I assume is causing this to happen.
 
Hey guys, new member here but not at all new to the sport. I thought I would share some interesting info that I learned in the last year. Apologies if this has been discussed before.

While working up a new load last year for my 300 RUM I noticed that my "fresh" loads (loaded within a day or two of shooting) had a considerably higher MV than loads that had sat for about two weeks or so. I am full length sizing all my brass the same way with a redding bushing die and the expander mandrel installed. All loads were the exact same specs but the fresh loads were around 3135 FPS with an ES of around 20 FPS and the 'seasoned' loads shoot around 3075 FPS with the same ES.

I know that a lot of benchrest shooters load and shoot immediately, even loading at their vehicle before the match. As a hunter I can't really do this so now I prefer to 'season' my loads for a couple weeks before shooting.

To back this up, a buddy of mine I shoot with noticed the exact same thing on his 6.5 CM while we were shooting together.

Simply put, I believe brass will 'stress relieve' over time which results in slightly less neck tension. This, I assume is causing this to happen.

Hey, JD, I'll be watching your thread here. I imagine that many a reloader has attributed this phenomenon to 'cold weld'. I never was entirely sold on the concept and may be leaning to your suggestion and may do some of my own research this summer.

Ken Taylor
 
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Hey Ken, so yeah this whole thing led me to the interesting phenomenon of 'cold weld'. So I did my own test regarding this. I do not have a PSI gauge on my press so this is somewhat subjective.

Last year I load two identical rounds, one with graphite lube applied to the neck and the other without. This was also on brand new shiny brass. I loaded them a little long so I could press them down a little and not push them in to far.

After letting each round sit in my garage over the winter for about 4 months or so I pressed each on down about .020" looking for increased pressure to seat or that 'pop' everyone talks about. I noticed no difference in seating pressure on either case. Maybe I didn't wait long enough?

I personally think that the bullet weld can be attributed to some sort of lube or corrosion from people hand oil/sweat when then handle the bullet. Sounds weird but working in the knife industry I have seem some people cause knives to rust in their pockets quicker than others.
 
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It’s an interesting concept and one that would seem to have some merit in some circumstances, I.e. brass that has not had stress relieved through annealing. So, a couple of questions for you:

Do you anneal prior to sizing? It’s been shown that annealing before sizing reduces spring back. Maybe this issue could be reduced.

Have you tested this theory at all? Since you have taken the time to test the lube/weld concept, could you not use the same type of test to verify if rounds created exactly the same except for annealed/non-annealed or new brass versus multi-fired brass show any re-seating variation after an extended period of time?
 
It’s an interesting concept and one that would seem to have some merit in some circumstances, I.e. brass that has not had stress relieved through annealing. So, a couple of questions for you:

Do you anneal prior to sizing? It’s been shown that annealing before sizing reduces spring back. Maybe this issue could be reduced.

Have you tested this theory at all? Since you have taken the time to test the lube/weld concept, could you not use the same type of test to verify if rounds created exactly the same except for annealed/non-annealed or new brass versus multi-fired brass show any re-seating variation after an extended period of time?

This is a very good point. So, the test I did and all rounds fired last year were from a new batch of un-fired Norma brass. I am pretty sure Norma anneals the brass from the factory so that's why I did not anneal. Also, I do not normal anneal between loadings which I probably should just never have.

When you down size the neck and then stretch it out with the mandrel you are still imparting some significant stress into the brass after you anneal it. So, I couldn't say for sure without annealing myself but my guess is that it will still have 'spring back' during its own relieving process.
 
I pulled down some year old 22-250 80g a max from a barrel that didn't last as long as expected. They had cold welded in. I had to use the seating die to break them loose so I could pull them with a collet puller. I think its highly doubtful the amount of force needed was because the necks tightened down little. This was 7x fired Lapua with no neck lube.
 
I pulled down some year old 22-250 80g a max from a barrel that didn't last as long as expected. They had cold welded in. I had to use the seating die to break them loose so I could pull them with a collet puller. I think its highly doubtful the amount of force needed was because the necks tightened down little. This was 7x fired Lapua with no neck lube.
A year on clean cases, I could totally see that.
 
Factory brass is waxed so your tests are invalid.
Also, brass hardens over time, not the other way around.

I size and tumble the brass before reloading which I would think would eliminate any wax in the neck. Also, I never said the brass softens over time. Brass does relieve stress over time and yes it also hardens in the process. I have found non-shooting scientific articles on this.
 
I think it’s something in your brass/neck prep causing this

I have 3 different match guns and about 9 barrels between them currently in different calibers...I routinely load 3-500 rounds for a barrel then shelf it until I shoot up my current batch/caliber, then I’ll switch barrels and shoot the stuff off the shelf...I’ve shot ammo in all of them that sat for 6 months to a year and I’ve never seen any velocity differences in it that could be anything more than temp/day to day variation related

I just shot some ammo in my hunting rifle yesterday that I loaded back February...it avg 3055 then, and was 3052 now On the LabR

Like mentioned above, in the past I’ve pulled bullets From boxes to check/measure something, then put that bullet back in the box...pull it out a month later, it’s tarnished, and when seating I can feel more drag....I’ve always been curious If getting skin oils between the bullet and brass necks Causes some form of corrosion also

when I’m seating bullets I typically wear gloves to keep oils out of the mix, idk if it helps, but I’ve never seen this issue lots of others talk about?
 
If you think you’re experiencing cold welding between the bullet and the brass, I would think you’d see pressures/speeds boost. My only experience was with 338 Lapua cases, wet tumbled with stainless pins. Similar experience to the op but with higher speeds and increased es/sd’s, same lots on everything. I could replicate the results, when I used graphite neck lube, everything fell back into place speed, es, sd-wise. I stopped cleaning with that process and resumed walnut media tumbling of the brass, never ran into the problem again. Thinking you’re problem may be something else that
I am not qualified to comment on
 
I size and tumble the brass before reloading which I would think would eliminate any wax in the neck. Also, I never said the brass softens over time. Brass does relieve stress over time and yes it also hardens in the process. I have found non-shooting scientific articles on this.

Brass does not stress relieve over time when it’s under tension from a bullet sitting in the neck. Brass hardens and stress increases and the neck eventually splits. That is why the brass is annealed at the neck at the factory prior to loading and why the military specifies the annealing mark be visible on the ammo they purchase.

Sizing and tumbling will not remove the wax from the inside of the neck. Shooting, then tumbling will.
 
Pull a bullet from a cartridge that has been sitting and measure your neck tension to see if it has indeed changed.