Mandrel as last step?

[Mikecr]

You're absolutely right about it all centering on load development.
No matter your reloading plan, with or without extremes.

I hope you understand though that our bullets are not expected to be pushed from necks. The PSI of gripping force I'm referring to is not that needed to push bullets through necks. Instead, it's a force needed to overcome(release) the grip on bullet bearing.
If a bullet could not release from a dry neck, let's say because the neck could not expand, and so the bullet had to be pushed out, your gun would explode right there. If you had a wet lube on your bullets (hydraulic bearing), then they could be pushed out with less drama. But your tested best CBTO could be dubious to manage.

 

[Alex Wheeler]

You can easily measure neck tension. You load groups with different neck bushings then you measure the only thing that matters. The target.

 

[Mikecr]

How do you incorporate bushing changing during load development?

 

[Mike Matteson]

Not a direct indication.
A prior thread about this: https://forum.accurateshooter.com/threads/seating-force-measurement.3985487/

Seating force is mostly frictional, which plays no internal ballistic role.
So we can only correlate seating force with 'relative' tension (roughly) -at carefully controlled/normalized friction.

True neck tension, amounts to hoop tension, provided by brass spring back force, against a bearing area (PSI).
It is possible to measure this force but there is currently nothing available for it on the market.
Given this, instead of trying to set force (which you can't measure right now), it's easier and more precise to adjust sizing LENGTH, which spring back force would apply to. It's also easier, and logical, to do this in a pre-seating operation, so that you can match it before seating bullets.

I'll go a long on that. Setting up and under sizing the neck the same on each case to start with. At least you would be some form of consistence. The brass is kind of the unknown on how it hold the bullet. So same lot of brass should help to be consistent. At the same time I will go back to cutting your case necks to a consistent thickness. There by the release would or should be the same all the way around. In my way of thinking. Some say it doesn't make any different. The long range shooter think not either. It would be hard to make me believe it doesn't. A thin pieces of metal moves far easier than a thicker pieces of metal or made to move at the time of releast.
The other is I haven't taken the time to set up, size and let the brass set for a day or so two, to see what the spring back is or going to be.

 

[Alex Wheeler]

How do you incorporate bushing changing during load development?

Mike, this is the easiest thing to test. Many things can move the node, like a primer change. However a bushing does not seem to do that. You can simply take your best load and just change the bushing. If I want to find the correct bushing first, I load a mini ladder, 5 shots around the node with each bushing. Usually its pretty obvious. Im not saying you dont already have to best nt for your combo, but I have turned rifles I was about to pull the barrels into excellent shooters by changing nt. It can make a huge difference. You need to shoot this at distance. I have had rifles shoot well at mid range, but were un tunable at 1k until testing this at 1k.

 

[Dragoon300]

Mike, this is the easiest thing to test. Many things can move the node, like a primer change. However a bushing does not seem to do that. You can simply take your best load and just change the bushing. If I want to find the correct bushing first, I load a mini ladder, 5 shots around the node with each bushing. Usually its pretty obvious. Im not saying you dont already have to best nt for your combo, but I have turned rifles I was about to pull the barrels into excellent shooters by changing nt. It can make a huge difference. You need to shoot this at distance. I have had rifles shoot well at mid range, but were un tunable at 1k until testing this at 1k.

That's interesting, and worth trying. It can be done with mandrels too. Do you see velocities change up or down with more or less tension? I can appreciate your testing at 1k too, easier to see a change, if you are experienced in 1k shooting. Otherwise small changes could get lost in the conditions.

 

[Willys]

I read a post from AW about not being afraid to bump up NT so I went to .0035 from .002 and it tightened verticle up at 1000. One more variable to test.

 

[BrentM]

Mandrel address brass neck thickness inconsistency better than a bushing. I still use a bushing and size down about .003 and then mandrel expand to .002 ish. If you see a neck base donut mandrels will address this too. I prefer it, no more 90% neck turning, great sd and accuracy.

 

[Dragoon300]

Mandrel address brass neck thickness inconsistency better than a bushing. I still use a bushing and size down about .003 and then mandrel expand to .002 ish. If you see a neck base donut mandrels will address this too. I prefer it, no more 90% neck turning, great sd and accuracy.

Totally agree

 

[SteveBurton]

Mandrel address brass neck thickness inconsistency better than a bushing. I still use a bushing and size down about .003 and then mandrel expand to .002 ish. If you see a neck base donut mandrels will address this too. I prefer it, no more 90% neck turning, great sd and accuracy.

This!

 

[Mike Matteson]

Mandrel expansion should be seen as a pre-seating action.
It does push most thickness variance outward -away from seating bullets. With this, bullets seat straighter.
Pre-seating expansion itself is needed to bias residual springback energy inward, against bullet bearing.
Otherwise, if last sizing energy is inward, then brass will eventually reach lowest energy level by counter expanding outward, away from bullet bearing. This, reducing tension over time.

We should always size necks outward last, before seating bullets. And truly we should not be upsizing necks with bullet seating.
Bullets ARE NOT neck sizers.
Bullet seating should expand necks no more than normal elastic limit (springback range), which is not actual upsizing/yielding.
For tension adjustments, we should adjust sizing length on necks, and not interference.

Then you are looking at neck sizing dies? Because FL dies are set up to bump the shoulder at the same time. With FL bushing dies can be ajusted to on size the neck or a portion of the neck. At least that what I ran into, or think I did. Never had used bushing dies until go to a 6mm/280AI case. I only done a few case at this time. Stepping down 4x to achieve ID or what I feel is the correct ID presently. Having the Smith sitting up a blank seating die with my reamer to complete the last step for the rifle presently. LEARNING!

 

[Mike Matteson]

This!

So you push the inconsistence to the exterior of the neck. Why not just cut the neck to take out the inconsistence thickness neck to start with?

 

[Willys]

You mean inside turning?

 

[SteveBurton]

So you push the inconsistence to the exterior of the neck. Why not just cut the neck to take out the inconsistence thickness neck to start with?

You absolutely can do that. Turning necks is an expensive and time consuming process. I went down that road several years ago but have been trying to simplify my process lately.
Also, most SAAMI chambers are cut with 0.010 clearance between the brass neck and chamber wall. Most SAAMI brass diagrams show an 0.016-0.018 thick neck wall. You start turning necks down and you increase that clearance which also works the brass in the neck more.