Neck Tension/Seating Pressure Question

[Dave Way]

Guys, I have a question for you. Yesterday I went to load up some 300 WSM ammo for a test of a new bullet. Let me describe my normal reloading process for you:

Clean carbon from outside of case necks with 3M pad
Anneal cases in AMP Annealer
Trim/Chamfer cases in Giraud power trimmer
Size cases is Redding S Type FL Bushing die
Clean primer pockets
Clean cases in vibratory tumbler with ground walnut hull media
Brush inside of necks with nylon brush in electric drill
Prime
Charge
Seat Bullet with Wilson in line seater and 21st Century Hydro Press

This method has yielded low run out, single digit SD's and some good groups at 1K for me. The reason for my question is I sort my loaded rounds by seating pressure from least to most using the hydro seater. Normally the gauge on the seater rises as pressure is applied- until the point where the bullet begins to move. This is the pressure I use to sort them by. At that point the gauge levels out until the seater bottoms out, at which it will spike.

Yesterday however, when I went to seat the bullets the pressure just slowly increased constantly until the seater bottomed out. Since I was testing a new bullet, and thinking that may be the cause, I loaded some of the bullets I normally shoot with the same result. Then I thought, the only change in my routine, and it wasn't really a change, just a timing thing, was that the cases that I went to load had been annealed, sized and cleaned at least two months prior, in fact they were still sitting in the tumbler.

So after that long introduction, my question is, do you think the long delay between case preparation and loading versus my normal case preparation and loading in a 24 hour period was the cause of the noted change in seating pressure? If so, why? Does the brass "relax" more "resting" for that extended period? I know a bunch of friends and I have shot some great groups fire-forming "virgin" brass. We can assume "virgin" brass has been "resting" for some time before we buy it. Annealing essentially returns brass to its 'virgin" state.

As I run multiple sets of match brass I plan on doing some testing with various amounts of time between case preparation/loading this spring including it's possible effects on SD and group size.

Curious to hear your thoughts-Dave.

 

[Dave Way]

Thanks Tom. I have heard that brass should get harder over time too. I could still sort these by neck tension however I would need to change my technique and use the last pressure before the die bottomed out. The interesting thing is the way the bullets started to move right away and the pressure kept increasing as more of the bullet entered the neck of the case which would make sense. That however would seem to indicate softer brass not harder brass like one would expect from sitting for an extended period.

Normally the pressure builds to a certain point until suddenly the bullet begins to move and you would think that would indicate harder brass/more neck tension which is the opposite of what one would expect when loading right after sizing.

 

[Willie]

Not sure it's pertinent to your regimen, but I size soon after annealing and use a bushing .003" under. When I get around to loading, I use an extra step by opening the neck up with a .002" under caliber mandrel, just prior to charging case. Seating has been smooth and consistent, plus SDs are mid single digits. Just a thought.

 

[T-shooter]

I use Imperial dry lube in the case necks before seating all bullets using their applicating media (small ceramic balls coated in the powder). It seems to help especially if the inside of the neck is cleaned too much or new cases that don't have any carbon yet.

 

[Richard Coody]

well i to used the 21st century shooting hydro press and found out pretty quickly if you were loading for ultimate accuracy you need to size and the rest of the process the night before going to the range. seating force goes up quickly after sizing. Don't know why just know what works. Rounds loaded the week before also didn't perform as well as the ones loaded the night before. undersizing and running a proper expander mandrel right before loading also.works but i found it.was just as easy to wait and resize just before loading.

Now many wouldn't notice the difference but for me it was the difference between high 2s and 1s and low 2s. sorting by seating force brings those groups right in.

 

[foxguy]

Dave,

I see my 6mms build to a peak and level off. But I don't anneal, so a lot of apples to oranges comparing notes here.

Tom

If I remember correctly( I am getting older) you are turning your necks, how many reloads are you getting out of your brass. Just wondering if after x number of reloads you go to new brass in order to continue shooting small groups.

Thanks

 

[Regnar]

Not sure it's pertinent to your regimen, but I size soon after annealing and use a bushing .003" under. When I get around to loading, I use an extra step by opening the neck up with a .002" under caliber mandrel, just prior to charging case. Seating has been smooth and consistent, plus SDs are mid single digits. Just a thought.

I am looking to do this. where are you getting your mandrel made? custom or off the shelf? i was looking at whiddens ser last night

 

[Richard Coody]

I am looking to do this. where are you getting your mandrel made? custom or off the shelf? i was looking at whiddens ser last night

K & M they will make whatever size you want.

 

[Bart B.]

The amount of interference fit between bullet and case is one cause for a given amount of seating force required.

The case neck hardness and thickness are two others.

The inside edge of the case mouth plays a small amount; more force needed if it's a rough sharp edge (often peels bullet jacket strips off), less if radiused and smooth (no jacket peeling).

 

[Richard Coody]

yep consistent neck tension is important and difficult to obtain

my technique
neck turn to a uniform thickness, anneal every firing, full length resize with a custom or simi-custom die, leave the carbon in the necks, light hand chamfer every time with a little rub with scotchbrite to polish it up., use an arbor press with a force indicator gauge to evaluate your procedure, sort by seating effort to find what your rifle likes. now this is taking it to the extreme but it works for me.

 

[Dave Way]

Thanks for the replies guys. It's always good to hear other's thoughts on a process that can be as variable as precision reloading. I had never entertained the expander mandrel idea but may test that. I know I will be testing to see if I can make any sort of correlation between the length of time between the initial annealing/sizing operation and then re-loading versus the SD's and or group size. If I come up with anything I will post it here. Dave.

 

[Bart B.]

Just wondering if after x number of reloads you go to new brass in order to continue shooting small groups.

A friend reloaded one 308 Win case 56 times shooting Sierra 168's into a 3/8ths inch group at 100 yards. 43 grains of IMR4895 in full-length sized cases. I had honed its neck to .002" less than loaded round neck diameter. Fired case shoulders' bumped back about .002" and case trimmed back to 2.000" every 10 shots.

 

[dmoran]

A friend reloaded one 308 Win case 56 times shooting Sierra 168's into a 3/8ths inch group at 100 yards...

Must have had some fantastic tunnel type conditions to get that kind of conditional control over the man hours it would have taken to only use one and the same case for 56-shots into a .375" group. Or there is other pertinent particulars that your leaving out to how it was actually accomplished.
Donovan

 

[Richard Coody]

Thanks for the replies guys. It's always good to hear other's thoughts on a process that can be as variable as precision reloading. I had never entertained the expander mandrel idea but may test that. I know I will be testing to see if I can make any sort of correlation between the length of time between the initial annealing/sizing operation and then re-loading versus the SD's and or group size. If I come up with anything I will post it here. Dave.

i have a k&m expandrel mandrel kit.

if you use a bushing die then the mandrel certainly helps. moves brass imperfections to the outside especially if you are using unturned brass. use a little tighter bushing and let the mandrel do the final sizing.

if you neck turn imperfections are less of a problem but i find that final sizing with a mandrel gives better control of neck tension. of course i have a set of mandrels in .0005 increments. final sizing just before charging and seating bullets is best.

 

[Bart B.]

Must have had some fantastic tunnel type conditions to get that kind of conditional control over the man hours it would have taken to only use one and the same case for 56-shots into a .375" group. Or there is other pertinent particulars that your leaving out to how it was actually accomplished.

He used a wood stocked Win 70 based rifle, 26" Hart 1:11 twist barrel, in a machine rest he had built that was clamped on a concrete bench. Essentially a rail gun setup. Reloaded that WCC58 match case then shot it every 2 minutes or so. 8200 feet elevation in the Rockies early in the morning. Calm wind.

 

[Richard Coody]

best group i ever shot with my bench gun back in the olden days before all this modern machinery. A shilen built .222 bench gun i took one case and loaded it at the bench 5 times. learned something from that.

 

[Regnar]

best group i ever shot with my bench gun back in the olden days before all this modern machinery. A shilen built .222 bench gun i took one case and loaded it at the bench 5 times. learned something from that.

Curious as to what you learned? and that is not being a wise ass, im serious.

 

[243winxb]

Does the brass "relax" more "resting" for that extended period?

Brass has a memory. https://depts.washington.edu/matseed/mse_resources/Webpage/Memory metals/how_shape_memory_alloys_work.htm

 

[Richard Coody]

Curious as to what you learned? and that is not being a wise ass, im serious.

well they were neck turned with the neck turner that came with the rifle and bullets were seated with a hand die that came with the rifle. powder was weighed on a beam scale. now you bave to remember this was in the late 70's.

i would say to me the consistency of using that single case proves that there is a reason to sort cases by weight, volume and whatever else you can do to make every piece of brass as identical as possible.

 

[Regnar]

well they were neck turned with the neck turner that came with the rifle and bullets were seated with a hand die that came with the rifle. powder was weighed on a beam scale. now you bave to remember this was in the late 70's.

i would say to me the consistency of using that single case proves that there is a reason to sort cases by weight, volume and whatever else you can do to make every piece of brass as identical as possible.

Thats good info. so you are saying that your test, along with Barts friends test one case, proves that case volume effects the comcistancy of the POI of the round?