What is your sizing/expanding method?

[fatelvis]

Hi Guys, I have 300 rounds of Once fired Lapua 6 BR brass that is ready to be reloaded. I’m trying to decide how much to size the necks down, and what size mandrel to use to open them back up. Please let me know what works best for you. All this brass is unturned blue box brass. Thanks!

 

[Bill Norris]

I measure my loaded neck diameter. Drop back .002 on the bushing and go.

 

[memilanuk]

I pick a nominal value - say 0.002" under bullet diameter - to start with. Generally I'll go with a mandrel of that size, as they are pretty commonly available. I'll check the resulting neck ID using pin gauges, and note it for future reference.

When it comes time to reload the fired cases, I'll experiment a little with said expander, and various bushing sizes, to achieve the same neck ID as before. I've had some experiences where the change in spring back of the neck between virgin and fired caused me some grief. Annealing seems to help, as does keeping track of the neck ID that the load was originally developed with.

Other times, if I'm feeling especially fussy - or if it just feels like it's not *quite* shooting the way I want it to... I may experiment with specific neck IDs to see if one value or another works better in that particular barrel.

 

[BartsBullets]

I size but don’t expand. I haven’t seen a need to work the case neck both ways. For long range I find a bushing that provides between 20 to 40 pounds of seating pressure.

Bart

 

[caihlen]

I size but don’t expand. I haven’t seen a need to work the case neck both ways. For long range I find a button that provides between 20 to 40 pounds of seating pressure.

Bart

How are you measuring this?

 

[Bc'z]

I size with a L.E. Wilson bushing die, or a Redding type S.
Expansion is done with a bullet.

 

[BartsBullets]

How are you measuring this?

I have a K&M and a 21st century arbor press that will give me the seating pressure.
Bart

 

[caihlen]

I have a K&M and a 21st century arbor press that will give me the seating pressure.
Bart

Cool. Thanks for that.

 

[Murray Brook]

I use a Redding body die to size my 6br case and bump the shoulder appx .0015-.002 and size the neck with a Lee collet die that gives me appx .0015 of tension. I get good run-out #'s this way and works great in my rifle. I believe the neck tension that works best in your rifle can only be found by testing several different #'s. JMO

 

[fatelvis]

I size but don’t expand. I haven’t seen a need to work the case neck both ways. For long range I find a bushing that provides between 20 to 40 pounds of seating pressure.

Bart

Thank you for all the responses guys. I like to see what the reloading gurus are doing behind closed doors! Lol
Could I ask what measurement of neck tension is equal to 20-40Lbs seating pressure? I realize that other factors affect seating pressure, but I'm using once fired Lapua, dry tumbled to leave the carbon in the neck, and brushed twice with a nylon brush before seating.

 

[Bill Norris]

I size but don’t expand. I haven’t seen a need to work the case neck both ways. For long range I find a bushing that provides between 20 to 40 pounds of seating pressure.

Bart

I have seen no improvement in accuracy by using a mandrel after the bushing. Just working the brass for nothing seems like.

 

[mikecr]

Seating force is not tension. It's friction. But with friction normalized, then seating force is a valid comparative check.

I bushing downsize 2thou under cal for no greater length than seated bearing, & mandrel expand at 1thou under cal.

 

[mikecr]

I have seen no improvement in accuracy by using a mandrel after the bushing. Just working the brass for nothing seems like.

There is a difference -over time.
Brass initially springs back counter to last action, but it isn't over right there. It continues over time(or tries) to reach lower energy levels.

So initial tension with downsized(only) necks will decrease over time.
Tension with expanded necks cannot change while against bullet bearing.
Where you want good loaded ammo months down the road, you're better to expand(pre-seat) necks.

Expansion also pushes some thickness variance and donut outward, away from seating bullet bearing.

 

[Bc'z]

There is a difference -over time.
Brass initially springs back counter to last action, but it isn't over right there. It continues over time(or tries) to reach lower energy levels.

So initial tension with downsized(only) necks will decrease over time.
Tension with expanded necks cannot change while against bullet bearing.
Where you want good loaded ammo months down the road, you're better to expand(pre-seat) necks.

Expansion also pushes some thickness variance and donut outward, away from seating bullet bearing.

Annealing every firing should help to maintain consistency.
Bushing dies only size roughly 3/4 of the neck, with the proper combination of bullet and throat of chamber, donuts should become a non issue.
Or I'm doing it all wrong. Lol

I think it comes down to what works for each individual in the technique/method they chose to use to skin the cat.

On another note, after using a expander mandrel for turning necks I have followed up with a bushing die to get my .002 tension I like to start with for load development.

 

[JFrank]

Thank you for all the responses guys. I like to see what the reloading gurus are doing behind closed doors! Lol
Could I ask what measurement of neck tension is equal to 20-40Lbs seating pressure? I realize that other factors affect seating pressure, but I'm using once fired Lapua, dry tumbled to leave the carbon in the neck, and brushed twice with a nylon brush before seating.

Those should seat smoothly with touch of carbon left in the necks, I use enough bullet hold to seat +.025 and maintain cbto if I pulled a loaded round.
I have tested bushings against each other with the extra hold a clear winner for consistency on paper at 1000 yards. The main take away from this is to set up a target at 500 or more and test bullet hold side by side and draw your own conclusions.

J

 

[Ledd Slinger]

Any which way you bush and expand is up to you. Ladder testing will tell you what the rifle likes. I’ve had many instances where more neck tension shot better.

But a big key to consistent seating pressure, and thus grip/release of the bullet, is to run a nylon brush in the necks really fast multiple times with equal strokes on each case neck to smooth out the carbon. I run about 3 or 4 full strokes in and out on each neck. For that task I only use nylon brushes from “Montana Extreme”. Any other nylon brush is too soft and won’t give you as good consistency with pressure when seating bullets.

I personally like expanding along with a neck bushing because it lets me feel the case necks ‘before’ seating the bullets. Pretty easy to tell when one is too light or too tight and I can move it into the sighter/fouler pile. Sometimes if too tight a few more brush strokes will make it right.

 

[mikecr]

While seating force is a matter of friction (not tension), the target results will not show it.
Bullets are not pushed out of necks. They're released from necks.
Neck tension is that squeeze force gripping bullet bearing, provided purely by spring back force.

Example: If you were to fully anneal necks, you would likely find seating forces increased, but tension is dramatically lower as measured by a drop in MV.
On the flip side, if you dry coat bullets with WS2, you would find seating forces decreased, but tension is exactly the same as measured by same MV.
Adjust the LENGTH of neck sizing, and MV will follow this, as the gripping force is spring back force X area gripping (PSI).

 

[Ledd Slinger]

I agree that the bullet is released, hence why I used the terms “grip/release”. But the bullet would have to move forward some amount before the neck fully releases the bullet. That movement has to do with the friction factor and can change chamber pressures. Ignition starts in the rear, thru the middle of the charge to the base of the bullet, then outward in all directions. So a high friction neck may not allow the bullet to move forward until fully released during full ignition (higher pressure) where a low friction neck might allow the bullet to start moving prior to full release/ignition (lower pressure). If I don’t brush the carbon in my necks, it can show up on target in the form of fliers. If there was a way to control equal amounts of high friction on a case neck for seating pressure then I expect the consistency on target would be exactly the same as equal amounts of low friction, but that’s not easily accomplished since you don’t know what’s gonna happen if you don’t brush them. Could avoid brushing then sort them with a seating pressure gauge but I think you’d have too many separate groups. Kinda like sorting Hornady bullets. LOL!

The few renowned 1K BR shooters I know like to seat bullets at the range on each day of the shoot and brush the carbon in their necks to avoid any case weld on the bullet. If friction wasn’t an issue, I don’t think they would worry about brushing necks or loading rounds the morning of each day’s relays

 

[mikecr]

Cold welding doesn't happen in a day. It takes a long period of moisture exposure.
I always run a nylon brush through necks for a fresh carbon layer. This normalizes friction for consistent seating force and ease of reaching desired CBTO.

I agree that bullets will move under enough pressure, even if necks did not expand at all.
However, if the powder did have to overcome pull friction, the peak pressure would be higher than it is.
And an interference fit with chamber would present an immediate danger.
But this does not happen (normally).

If a neck expands only ~1/billionth of an inch, the bullet is swinging in the wind, freely released.
There is nothing griping a bullet after neck expansion.
Now consider how little of force per area it takes to expand a neck so little.
That's what we're dealing with, and what I'm telling you here passes tests.

I can double or halve normal seating forces purely due to neck/bullet frictional changes, with no change to neck tension itself. This has zero affect to MV or tune.
Then, I could tweak tension only, and see immediate affects.
It's very important to understand the difference.
Friction and tension have nothing in common.