Neck Tension Changing?

[Davidheart]

Do any of you find your neck tension will "settle" or reduce after resizing using a standard FL sizer? I have a batch of 308 LC LR 12 brass I cleaned using SS pins, annealed, FL sized, trimmed, and loaded all in a two day span. I loaded CFE223 in 0.3gr increments to do some testing with a 168gr A-Max up to 46gr.

I shot my loads at 44.5gr and 44.8gr and received low SDs (7fps and 4fps respectively) and .610 and .330 5 shot groups respectively and 2600fps and 2615fps respectively from an 18" barreled 6.5lb rifle. It was awesome!

Then it started to rain and I called it a day. The next couple days were very windy so I decided not to shoot for groups in strong wind.

4 days later I back out to shoot the subsequent groups. I went through 45.1gr and 45.4gr..... and saw some strange results.... so I shot another group of 44.5gr and decided to stop. All three groups opened up past 1.5" and SD's went closer to 30fps! Completely different from my previous result and very very mind melting.

I then went to load a couple more last night to try my groups again and noticed significantly more tension upon loading! Is it possible there was a fair amount of springback after loading my other groups causing pressure spikes and/or inconsistent neck tension? Or is it because I used SS to clean my brass and the inside of the necks are so clean I need to hit them with some graphite before loading again?

Very confused and would appreciate some additional input! Thank you.

 

[Ccrider]

No way to tell. Do everything the same. Change one thing at a time and judge for yourself the effect.

 

[drop_point]

Was all the brass prepped at the same time?

I've never been able to measure any spring back.

Also, single five round groups aren't enough to really establish accuracy or SD.

 

[Bill Norris]

Within 4 days lots of other changes could have occurred. Atmospherics, barrel condition (cleaned or not) , and general set-up come to mind.

 

[Mike TackleBerry]

Humidity would be my guess.

 

[JFrank]

Could have pinged up the case necks a bit with those SS pins, obviously you’ve discovered increased friction.
Can you post the tuning ladders ?

 

[Straightshooter1]

Do any of you find your neck tension will "settle" or reduce after resizing using a standard FL sizer? I have a batch of 308 LC LR 12 brass I cleaned using SS pins, annealed, FL sized, trimmed, and loaded all in a two day span. I loaded CFE223 in 0.3gr increments to do some testing with a 168gr A-Max up to 46gr.

I shot my loads at 44.5gr and 44.8gr and received low SDs (7fps and 4fps respectively) and .610 and .330 5 shot groups respectively and 2600fps and 2615fps respectively from an 18" barreled 6.5lb rifle. It was awesome!

Then it started to rain and I called it a day. The next couple days were very windy so I decided not to shoot for groups in strong wind.

4 days later I back out to shoot the subsequent groups. I went through 45.1gr and 45.4gr..... and saw some strange results.... so I shot another group of 44.5gr and decided to stop. All three groups opened up past 1.5" and SD's went closer to 30fps! Completely different from my previous result and very very mind melting.

I then went to load a couple more last night to try my groups again and noticed significantly more tension upon loading! Is it possible there was a fair amount of springback after loading my other groups causing pressure spikes and/or inconsistent neck tension? Or is it because I used SS to clean my brass and the inside of the necks are so clean I need to hit them with some graphite before loading again?

Very confused and would appreciate some additional input! Thank you.

Yes, after sizing your brass, there will be an initial spring back and over ~24 hr period a little more. To see how much, simply measure the necks after you've sized them and then again the next day and see the difference.

How much spring back you'll see will depend on a couple of things. The main thing is how much work hardening is taking place with your sizing operation. If you're not properly annealing after every firing, every time you size the brass the more work hardened the case gets and the more springback you'll experience. Another thing that's involved with how much springback one can have is the thickness of the neck wall AND the diameter of the neck (so the caliber one is dealing with is part of the issue).

Don't confuse what we call "neck tension" with the interference fit, interference referring to the friction between the bullet's bearing surface and the case neck wall. Neck tension has to do with how much pressure it'll take to expand the neck and release the bullet. Interference is a very small factor on bullet release, but it can have a great effect on the seating depth consistency.

Wet tumbling with pins get the interior of the necks nice and clean and even shinny, and that tends to result in quite a bit of interference fit. To reduce that, one will need to use some kind of lube. . . or figure out an approach to not remove much of the residue left after firing.

The goal is for consistent seating depth and consistent release of the bullet. My solution is not wet tumbling with pins (just hot water and Dawn will do), but dry tumbling with rice after sizing. And of course, I anneal after every firing.

 

[Ccrider]

Within 4 days lots of other changes could have occurred. Atmospherics, barrel condition (cleaned or not) , and general set-up come to mind.

This is what I was thinking and why I said no way to tell. One or two good groups do not tell you anything. Also, different days, different temps, humidity and bp— different results, and moreso if the gun is not in tune to begin with. No way anyone is going to be able to answer your question, other than to tell you it’s possible.

 

[mikecr]

For testing, I make a testing batch a couple hours before shooting it.
For hunting, I test & use (if good) ammo made months beforehand. What I call seasoned ammo.

I do this because brass continues to counter last energy added over time.
And with this, I add as little energy as viable.

I think you maybe doing too much to your brass for consistency.

 

[L.Sherm]

Have you tried not annealing?

 

[JFrank]

moreso if the gun is not in tune to begin with. No way anyone is going to be able to answer your question, other than to tell you it’s possible.

This ^^ is what I was thinking with regards to repeatability. I don’t see temps changing a load drastically unless it’s already edgy.

 

[Davidheart]

This ^^ is what I was thinking with regards to repeatability. I don’t see temps changing a load drastically unless it’s already edgy.

Genuinely, this rifle tends to shoot under 1" no matter what I stuff down its pipe. I doubt the rifle is that bad. I also don't see my groups opening up from .6 and .3 to 1.4 unless something dramatic happened. Yes, extreme weather changes could effect loads, but I've never seen it happen so dramatically.

I created myself another batch from the same brass. 5 with mica on the inside of the necks, 5 with graphite, 5 with nothing new but an expander mandrel run through the necks, 5 with an expander mandrel and graphite, 5 from the original sizing with no changes (unless the neck spung back).

When I created these batches I'm going to say, the ones that didn't have the expander mandrel run through them felt excessively tight.... we'll see if it shows up on paper.

 

[Davidheart]

As a follow up I haven't shot the batches I made yet but I did resize and measure the OD using an OD micrometer on Friday night (it's Monday morning). The neck reduced from being .3375 to .3365 in the course of three days.

 

[drop_point]

What did you measure them with? Did you measure neck thickness and check for variance?

It sounds like if they feel tight seating the bullet without the expander, you're introducing a huge variance.

You say the gun always shoots tighter, but you are changing lots of variables at once. 1.4" isn't out of the realm of possibility with what you're doing.

 

[Davidheart]

This is a fresh batch of brass I haven't worked with yet. I measured with a 0.0001 outside micrometer. The dial type that goes from 0-1". Not a Mitutoyo caliper like we use to measure OAL.

I resized/expanded them, then let them sit for a while. The cases which sat for a while feel tight while seating. However, if charged and seated immediately following expanding they feel normal. Also, if I send the expander mandrel in brass which has sat a few days they again feel normal. Clearly I'm having spring back which is causing my issue.

My gun shoots tighter using known brass I've worked with before. It's a Lilja barrel chambered to BR specs using an Alpha reamer with a trued and bushed bolt. After ~1k rounds sub MOA is typical. Of course a total crap load could be throwing me off but it's not what I'm used to seeing in this rifle.

I'm wondering if the spring back I'm dealing with is a result of using this particular batch of Lake City LR brass. Clearly there's about .001 of spring back I should account for. Another variable is pin cleaning and seating bullets in perfectly shiny necks without lube which could cause issues too.

A solution could be just using this brass for cannon fodder doomsday preps and just go pick up some Alpha/Lapua/Peterson for serious work.

 

[JFrank]

seating bullets in perfectly shiny necks without lube which could cause issues too.

shiny clean adds a lot of friction when seating , does that transfer to the target though ?

 

[drop_point]

This is a fresh batch of brass I haven't worked with yet. I measured with a 0.0001 outside micrometer. The dial type that goes from 0-1". Not a Mitutoyo caliper like we use to measure OAL.

I resized/expanded them, then let them sit for a while. The cases which sat for a while feel tight while seating. However, if charged and seated immediately following expanding they feel normal. Also, if I send the expander mandrel in brass which has sat a few days they again feel normal. Clearly I'm having spring back which is causing my issue.

My gun shoots tighter using known brass I've worked with before. It's a Lilja barrel chambered to BR specs using an Alpha reamer with a trued and bushed bolt. After ~1k rounds sub MOA is typical. Of course a total crap load could be throwing me off but it's not what I'm used to seeing in this rifle.

I'm wondering if the spring back I'm dealing with is a result of using this particular batch of Lake City LR brass. Clearly there's about .001 of spring back I should account for. Another variable is pin cleaning and seating bullets in perfectly shiny necks without lube which could cause issues too.

A solution could be just using this brass for cannon fodder doomsday preps and just go pick up some Alpha/Lapua/Peterson for serious work.

So in other words, you've not used this brass. This brass is the first suspect.

Using pins can also create some issues, I'd look really close and make sure you aren't peening the necks.

 

[Webster]

Do any of you find your neck tension will "settle" or reduce after resizing using a standard FL sizer? I have a batch of 308 LC LR 12 brass I cleaned using SS pins, annealed, FL sized, trimmed, and loaded all in a two day span. I loaded CFE223 in 0.3gr increments to do some testing with a 168gr A-Max up to 46gr.

I shot my loads at 44.5gr and 44.8gr and received low SDs (7fps and 4fps respectively) and .610 and .330 5 shot groups respectively and 2600fps and 2615fps respectively from an 18" barreled 6.5lb rifle. It was awesome!

Then it started to rain and I called it a day. The next couple days were very windy so I decided not to shoot for groups in strong wind.

4 days later I back out to shoot the subsequent groups. I went through 45.1gr and 45.4gr..... and saw some strange results.... so I shot another group of 44.5gr and decided to stop. All three groups opened up past 1.5" and SD's went closer to 30fps! Completely different from my previous result and very very mind melting.

I then went to load a couple more last night to try my groups again and noticed significantly more tension upon loading! Is it possible there was a fair amount of springback after loading my other groups causing pressure spikes and/or inconsistent neck tension? Or is it because I used SS to clean my brass and the inside of the necks are so clean I need to hit them with some graphite before loading again?

Very confused and would appreciate some additional input! Thank you.

How do you anneal. Whats the temperature you are trying to hit? 750F does zero annealing. No-one knows who made up this number. A lot of accurate annealing data related to temperature has been put up on this website.

 

[JFrank]

This is a fresh batch of brass I haven't worked with yet. I measured with a 0.0001 outside micrometer. The dial type that goes from 0-1". Not a Mitutoyo caliper like we use to measure OAL.

I resized/expanded them, then let them sit for a while. The cases which sat for a while feel tight while seating. However, if charged and seated immediately following expanding they feel normal. Also, if I send the expander mandrel in brass which has sat a few days they again feel normal. Clearly I'm having spring back which is causing my issue.

My gun shoots tighter using known brass I've worked with before. It's a Lilja barrel chambered to BR specs using an Alpha reamer with a trued and bushed bolt. After ~1k rounds sub MOA is typical. Of course a total crap load could be throwing me off but it's not what I'm used to seeing in this rifle.

I'm wondering if the spring back I'm dealing with is a result of using this particular batch of Lake City LR brass. Clearly there's about .001 of spring back I should account for. Another variable is pin cleaning and seating bullets in perfectly shiny necks without lube which could cause issues too.

A solution could be just using this brass for cannon fodder doomsday preps and just go pick up some Alpha/Lapua/Peterson for serious work.

A friend of mine experienced a bit of spring back on relatively new brass although by brushing debris out and adding a bit of lube the bullets seated on and shot very well, personally I like as much bullet hold as I can get and the target tells me when it’s too much.

 

[gunsandgunsmithing]