Redding S bushing die and expander ball

[BoydAllen]

If a bushing die is used with unturned necks, so that the neck is not sized down too far, before expanding, resulting in much straighter brass than if a typical one piece die, use of an expander ball will not make the case crooked but it will give more uniform neck tension. Evidently it is brain surgery. A long time 1,000 yd. benchrest shooter, who has done well in the sport, once told me that the last step in his sizing process is to use an expanding mandrel to open up his bushing sized, turned necks slightly, because he gets better results that way. He has a set of expanders in half thousandth increments. This is not some theoretical discussion. I have done exactly what I am posting about.

 

[CatShooter]

If a bushing die is used with unturned necks, so that the neck is not sized down too far, before expanding, resulting in much straighter brass than if a typical one piece die, use of an expander ball will not make the case crooked but it will give more uniform neck tension. Evidently it is brain surgery. A long time 1,000 yd. benchrest shooter, who has done well in the sport, once told me that the last step in his sizing process is to use an expanding mandrel to open up his bushing sized, turned necks slightly, because he gets better results that way. He has a set of expanders in half thousandth increments. This is not some theoretical discussion. I have done exactly what I am posting about.

I'm not sure how this tale of a 1,000 yard benchrest shooter's case prep applies to the original question, but if that is your idea of brain surgery, I'm applying for operating privileges at the local hospital.

I am not sure what this sentense means...

"If a bushing die is used with unturned necks, so that the neck is not sized down too far, before expanding, resulting in much straighter brass than if a typical one piece die, use of an expander ball will not make the case crooked but it will give more uniform neck tension."

Can you explain it, please? I have an over the counter, Remington .220 Swift, with a SAAMI chamber.

The SAAMI neck for a .220 Swift is very large (probably because the dimensions were set 80 years ago, and based on an experimental military case)... so a fired case is 10 thou (0.010") larger than a necked sized, and loaded neck.

I run fired cases (un-turned, factory Norma) through a Redding Comp NECK sizer in one pass, and the neck TRO (total run out) is ~1 thou (~0.001").

How much better does it need to be, and how much better can you get it, by sizing it smaller and then expanding it?

 

[Lapua40X]

How much better does it need to be, and how much better can you get it, by sizing it smaller and then expanding it?

I can't speak for others, but in my case it isn't about making a neck smaller and then expanding it, it's about ensuring that the case neck is as straight as possible. Even a bushing die, depending on the bushing's alignment with the die body, can tweak a case neck to some extent and the expander mandrel can help correct that condition. I've found the run out on some of my case necks (not always but certainly sometimes) fresh out of the bushing die have greater run out than others and running them over the expander mandrel improves the run out results.

 

[mikecr]

For unturned necks, mandrel expansion pushes thickness variance outward, allowing straighter seating.

Also;
1st - Neck tension is not the interference fit you initially leave with a die. Neck tension amounts to the grip on bullets that springback provides.
2nd - Springback changes with time, continuing to counter last energy added. If your last sizing action is inward, the brass springs back outward, and continues to do so over time until a minimum energy balance is regained.
If last energy added was outward, necks will continue to springback inward(increasing bullet tension). When you size brass to yielding, you change it's stored energy, and it's balance(it get's 'harder').
This happens everwhere brass is sized, including primer pockets.

Sinclair mandrels expand necks to ~cal, and then necks spring back to grip bullets. That is your true tension regardless of sizing(it's perfect). Your going to do this no matter what as bullet seating is expanding, but there is no good in high seating forces.
Pre-expand with a mandrel to drive any thickness variance outward, and allow necks to springback naturally for moderate seating forces and just as much grip as you'll get no matter how much you size. If the ammo isn't shot immediately, tension will go up a small bit over time, instead of down.
And don't clean necks to squeaky clean. This only serves to increase seating forces.

 

[BoydAllen]

When an unturned neck is sized with no expander ball or mandrel used, the irregularities show up on the ID rather than the OD. Choosing ones bushing size so that the expander ball can barely be felt as it passes through the neck, the ID of the neck is made more uniform, but the amount of pull on the neck is so slight that the case will not be made less straight by pulling it through the neck. With one piece dies that over size neck to a degree that is impractical for good bullet seating unless some sort of expanding is done, I have found that using an expander die and mandrel works much better than an expander ball, with regard to the straightness of the resultant ammo. If the ID of a case neck was in perfect alignment with the body of its case, taking a reading off of the OD of the neck would show runout equal to the variation in thickness of the neck, which is why it is better to check unturned brass, with a bullet seated, since it is the alignment of the bullet to the body of the case that is the major concern.

 

[LHSmith]

Sinclair mandrels expand necks to ~cal, and then necks spring back to grip bullets. That is your true tension regardless of sizing(it's perfect). Your going to do this no matter what as bullet seating is expanding, but there is no good in high seating forces.
Pre-expand with a mandrel to drive any thickness variance outward, and allow necks to springback naturally for moderate seating forces and just as much grip as you'll get no matter how much you size.

Well sometimes high is good when you want to build up pressure: typical current BR load of N-133 in a 6 PPC ....Likes HIGH N.T. as in 0.256 bushing on 0.0082 nks. in a .262nk. chamber w/ 0.002 total clearance.
Re: the 2nd para. ??............I run tighter bushings (after annealing) to bring those cases that had minimum NT up to the same tension as the rest of the cases.

 

[mikecr]

You may have missed my point.
Downsizing more does not create anymore tension. It only increases seating forces.
Annealed brass that's not expanded increases seating forces -while producing lower tension, until it's re-hardened(through sizing cycles).

If I shot a 6PPC, and of course needing extreme pressure, the last thing I'd be doing is over sizing and annealing. I'd size the correct amount including expanding, so that I never need to anneal, so that bullet grip remains highest.

 

[searcher]

The "problem' with not annealing is the progression of hardness and loss of spring. Too difficult to control as you are chasing the evolution of the changing neck continuously. Much easier to anneal on a regular basis - with the frequency set for what works best with that cartridge/load. I personally have never had a problem getting enough tension on a newly annealed case. I load my heavy bullets in one of my match A/R's using heavy enough tension (.005") that my bullets don't move in the cases - despite having no cannelure. And, because I anneal the cases on that gun every time, they are as close to the same everytime as I need them to be.

 

[mikecr]

The "problem' with not annealing is the progression of hardness and loss of spring.

Except harder brass springs back MORE...
You should review what's going on here.

The need for annealing comes down to a sum of choices right up front.
As long as you developed your load with continual annealing, and you're happy with the results, you should stick with it.
For those who develop loads with ~new brass hardness, and you're happy with the results, you should stick to minimal sizing.
If you chose a poorly designed cartridge, like a 30-06, well then you don't get the minimal sizing option, and annealing and lots of trimming and continual capacity variance and high runout, are the results of your choice.

 

[Turbulent Turtle]

Great, and I just gave up popcorn.