we measure neck tension by saying" .001 or .002 neck tension". this obviously is a measure of the neck's expansion after seating the bullet. i doubt the pressure between the bullet and neck stay the same over time. my suspicion: a seated bullet stretches the neck until an immediate equilibrium is reached, but i don't think it stops there. over time the residual pressure against the brass causes it to continue to "relax" until the force stretching the brass(from the bullet) equals the resistance in the brass. this process must vary depending on the condition of the brass...new and annealed or old and hardened. my reasoning for pondering this phenomenon is that i work up loads by loading and usu shooting in the next few days. i repeat a good load 3 times and consider it real and will load a number for later target or varmint shooting. 6+mos later that one hole group is not there! i know there are a lot of other variables but neck tension changes must be a significant internal change. i also suspect once the above reaches that equilibrium over time the brass hardens thereby resisting the necessary stretching required to release the bullet. ?"cold bonding " at it's worse...i pulled some bullets seated 1 year ago and my hornady collet puller was strained to the max! FWIW my suspicion...am i all wet?
neck tension changes with time?
- Thread starter lpreddick
- Start date
My theory is that brass is kind of fluid when sized. The after the sizing operation the brass moves in the direction that the sizing took place. i.e. inward with a bushing die and outward with a collet neck die. This movement will continue for a few days after the sizing operation took place until the equilibrium, that you have mentioned, is achieved. The phenomenon has been observed by many and discussed a lot on many threads on this and other sites.
I neck size with a Lee Collet Neck die, and when I do so, I let the brass 'rest' for a few days. If I were to seat bullets immediately after neck sizing the seat force is markedly greater than that of brass that has been 'rested'. Also neck tension that is felt is more variable. Brass sized with a bushing type die is the opposite. Bullets seated immediately after sizing 'feel' easier to seat with less tension variability than that of bullets seated in cases that have been sized and left to sit for a few days.
Therefore, when I load I tend to seat bullets right away if I am using a bushing type die, and I wait a few days if I use a Lee collet sizer. Also, to avoid the 'cold weld' phenomenon in preloaded ammo, I seat bullets .020" long and re-seat to the correct depth right before I am ready to shoot these rounds in a match.
There are many other opinions on this subject, but this is what has worked for me.
I neck size with a Lee Collet Neck die, and when I do so, I let the brass 'rest' for a few days. If I were to seat bullets immediately after neck sizing the seat force is markedly greater than that of brass that has been 'rested'. Also neck tension that is felt is more variable. Brass sized with a bushing type die is the opposite. Bullets seated immediately after sizing 'feel' easier to seat with less tension variability than that of bullets seated in cases that have been sized and left to sit for a few days.
Therefore, when I load I tend to seat bullets right away if I am using a bushing type die, and I wait a few days if I use a Lee collet sizer. Also, to avoid the 'cold weld' phenomenon in preloaded ammo, I seat bullets .020" long and re-seat to the correct depth right before I am ready to shoot these rounds in a match.
There are many other opinions on this subject, but this is what has worked for me.
300 RUM
Gene Nowaczyk
Ok I know your all going to hate me for this.
Brass has a memory to it unless annealed so;
If you size the necks after an anneal , it will not return to it's original memory as much but it will spring back some, when you apply a load such as a sizing die does the load remains in place for some time until visco relaxation is reached.
If you size a case that has not been annealed it will have more memory (spring back), over time the case neck will stress relax itself, it may not return fully to its original size, but it will grow larger.
Ok to keep this from getting to be 500 pages, it's simple the lees you work the neck the better right. The problem is for example you have a .308 in which the neck measures .339 after firing and them measures .333 after sizing and a bullet in placed it. If you choose the right bushing and anneal your cases you will not have issues on the long haul.
And it is almost impossible for brass to " cold weld" itself together with copper
lpreddick your quote of " a seated bullet stretches the neck until an immediate equilibrium is reached", not true it is not the bullet effecting the brass, but the brass returning to it's original state.
To be honest I load hundreds of round at a time, seating the bullet long and re-seat to proper length just before a match out of convince. On the other hand I have loaded rounds that have sat for 6+ months and they shoot just as well. To be honest one hole groups don't happen on their own and realistically ammo loaded today shooting one hole will still shoot one hole 1 year from now.
Brass has a memory to it unless annealed so;
If you size the necks after an anneal , it will not return to it's original memory as much but it will spring back some, when you apply a load such as a sizing die does the load remains in place for some time until visco relaxation is reached.
If you size a case that has not been annealed it will have more memory (spring back), over time the case neck will stress relax itself, it may not return fully to its original size, but it will grow larger.
Ok to keep this from getting to be 500 pages, it's simple the lees you work the neck the better right. The problem is for example you have a .308 in which the neck measures .339 after firing and them measures .333 after sizing and a bullet in placed it. If you choose the right bushing and anneal your cases you will not have issues on the long haul.
And it is almost impossible for brass to " cold weld" itself together with copper
lpreddick your quote of " a seated bullet stretches the neck until an immediate equilibrium is reached", not true it is not the bullet effecting the brass, but the brass returning to it's original state.
To be honest I load hundreds of round at a time, seating the bullet long and re-seat to proper length just before a match out of convince. On the other hand I have loaded rounds that have sat for 6+ months and they shoot just as well. To be honest one hole groups don't happen on their own and realistically ammo loaded today shooting one hole will still shoot one hole 1 year from now.
300 RUM said:
I agree 300 RUM, I have loaded rounds that have sat for months then take them to a match and they shoot the same as when I loaded them months back, however rifles DO change. As we shoot them the barrels begin to deform on the inside and they will definately change the way they shoot!
300 RUM
Gene Nowaczyk
BlackKnight755 said:
I store my pre-loaded ammo in dry box's with descent along side my powder and primers. Most of today's powders and primers have a very long shelf life a minimum or 10 years and in most cases up to 50 years, about the same for primers. If you doubt my statement I suggest you do your home work before commenting.
If you want the most out of your brass size them and wait 30 days to load them. On the other hand if you size them and just waited 24 hours to load, most of the brass spring back will be complete.
Think of your rifle like a pair of shoes they start off wonderful but after a while the start to hurt your feet, the shoes change not your feet in most cases.
I'll agree with the thought that neck tension relaxes with time and probably all other "sized" parts of the brass. I usually soft seat my 6mm to a very light neck tension of approx 1/2-3/4 thou. A recent state shoot was coming up and I was going to be out of town for the two weeks prior and had no choice but to preload all the ammo 3 weeks before. Didn't notice any accuracy changes as I started out with a 200-10x but I sure did notice two rounds that were soft seated so light that after the neck had "relaxed" the bullets had actually fallen down into the case. My guess is the necks had "relaxed" approx. a half thou. over the 3 weeks they sat in the box. I usually do try to load the week of the event. Eric in DL
for all my earlier shooting i would find a load /bullet combo that when jumped into the lands would at least cloverleaf. varying the jump usu did this quickly. i would then load 20-30 and wait for varmint season to open. the gun was not shot during that time, so no "change" in the gun. sometimes the cloverleaf would still be there and sometimes not! the temperature had changed, so i tried seating the bullet .005 thous deeper, then .10 thous deeper to find the one hole again. so many times i would hear a little "pop" as the bullet moved. ? cold bonding...not going there...recently tried pulling loads that were 1 yr old and the bullet was nearly destroyed by the hornady collet puller which works like a charm on recently loaded rounds. bullets falling into the case after seated very lightly. these observations suggest to me that the neck tension at the moment of seating changes with time. seems that it initially relaxes, which makes sense in that the brass is stretched by the bullet and the brass has to resist to hold the bullet. for every action there is an equal and opposite reaction...the brass continues to respond until??? an equilibrium of forces? what happens next over time? brass will harden as it ages, so does the grip on the bullet increase? one piece of brass is different esp if some were recently annealed and some not. so many variables and we can affect just a few.
Like I mentioned, further equallibrium counters last action.
If the last action is downsizing(like Cake's necks), spring back continues outward after initial. His last action was downsizing, because it left necks less undersized than a seating bullet would re-upsize. So his neck tension(grip) can be expected to drop a little bit over time. This is common.
When downsized enough that bullet seating will upsize, then upsizing is the last action. With this springback is inward, and can continue inward after initial equallibrium is reached. And here tension can be expected to increase.
When you downsize, then expand necks before seating, you're back to Cake's scenario.
When you anneal necks, you directly affect this(by removing springback), which can be as bad as good.
This is why there can be no set rule in it without qualifiers.
And necks are not unique in this. All brass sizing initiates the variable.
I for one have noticed that changing tension, HS, H20 capacity, and primer strike, affects tune.
So I load develop with fresh ammo, - not old ammo.
If the last action is downsizing(like Cake's necks), spring back continues outward after initial. His last action was downsizing, because it left necks less undersized than a seating bullet would re-upsize. So his neck tension(grip) can be expected to drop a little bit over time. This is common.
When downsized enough that bullet seating will upsize, then upsizing is the last action. With this springback is inward, and can continue inward after initial equallibrium is reached. And here tension can be expected to increase.
When you downsize, then expand necks before seating, you're back to Cake's scenario.
When you anneal necks, you directly affect this(by removing springback), which can be as bad as good.
This is why there can be no set rule in it without qualifiers.
And necks are not unique in this. All brass sizing initiates the variable.
I for one have noticed that changing tension, HS, H20 capacity, and primer strike, affects tune.
So I load develop with fresh ammo, - not old ammo.
BoydAllen
Gold $$ Contributor
Do this simple experiment. Start with a uniform set of rifle brass, that is ready to size. Size half of it, wait a month and then size the rest and load it all. If you are paying attention, you will notice that it takes a little more force to seat bullets in cases that were sized a month before bullets were seated.
Another experiment would be to size all of the brass at once, and load half of the cases immediately, when wait a month and load the rest, both sets longer than what is desired. Then reset the seater for the correct (shorter) length and reseat the bullets, noting any difference between rounds that were just loaded, and those that were loaded a month before.
You can call it whatever you want, but I have personally experienced guilding metal jacketed bullets becoming stuck in the case necks in which they had been loaded to the degree that they could not be removed with an inertial bullet puller unless they were broken loose by being seated deeper in their cases, which caused a loud pop when they broke loose. This is not conjecture, but fact.
Another experiment would be to size all of the brass at once, and load half of the cases immediately, when wait a month and load the rest, both sets longer than what is desired. Then reset the seater for the correct (shorter) length and reseat the bullets, noting any difference between rounds that were just loaded, and those that were loaded a month before.
You can call it whatever you want, but I have personally experienced guilding metal jacketed bullets becoming stuck in the case necks in which they had been loaded to the degree that they could not be removed with an inertial bullet puller unless they were broken loose by being seated deeper in their cases, which caused a loud pop when they broke loose. This is not conjecture, but fact.
I might not be thinking about this correctly, but why is that? I would expect the opposite. Granted, I haven't done a controlled experiment, but I would expect sized brass to "relax" over a short period of time and move more towards its expanded state. Or is it a matter of brass that has been sized recently being more malleable?BoydAllen said:
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