Seating Force Measurement

[Mikemci]

What is the consensus here on the benefit of measuring bullet seating force?
If you decide it is of value, what are your thoughts/experiences, regarding the use of a K&M Force measurement ram type vs. a hydro press, like the 21st Century version, or any other ones out there worth considering?
Mike

 

[Dusty Stevens]

I like the k&m myself

 

[dogdude]

Mike, I've owned both..prefer the K&M..the dial indicator is Much easier too read than the 21st Century, sold the 21st to a buddy and he loves it. He's never owned a K&M.

 

[dgeesaman]

Personal opinion, trust the feel of the handle before investing in the fancier press. I have a K&M with force pack. I took off my indicator because I don’t need numbers to know which ones seat firmly, stutter, or seat softly.

If you’re already using an arbor press and are looking for a finer level of resolution, buy the press with the gauge. In my case my loading skills have not caught up to it yet.

David

 

[Bart B.]

While bullet seating force is popular and easy to measure, I think bullet pull or extraction force is more important.

http://forum.accurateshooter.com/threads/neck-tension.3985488/#post-37561343

Rarely are both ways going to be the same when firing happens some time after seating.

 

[mikecr]

Seating forces directly affect your ability to set bullets to desired CBTO without a big battle on your hands.
With friction carefully controlled, seating forces can indirectly show relative differences in neck tension.
There is currently no tool or method to directly measure neck/hoop tension.

I go a different path in measuring and adjusting tension via PRESEATING FORCES rather than bullet seating forces.
I also refer to neck expansion as preseating expansion.
To do this I incorporated an electronic force sensor into an expander mandrel die. The free mandrel presses against a force sensor and a simple indicator provides a relative reading. I'm comparing each neck to all in batch for the first round of measure, adjusting outliers, and validating all match with an additional round of measure.
Then I load ammo

 

[David Christian]

@Mikemci, I used a K&M with force pack for a bit. 3 observations. 1. I found no correlation between seating force and the impact on target or speed of the bullet. 2. I found that measuring seating pressure was just as easy by feel using a standard arbor press. 3. Once my case necks were dialed in (interference fit, neck hardness, and surface condition of the inside case neck and bullet surface) I saw and felt no difference in seating force.

 

[mikecr]

1. I found no correlation between seating force and the impact on target or speed of the bullet.

This can very well be as seating forces do not directly represent tension, nor any other internal ballistic matter. The notions of 'pull force' being synonymous with tension is dead wrong.

[QUOTE="David Christian, post: 37561768, member: 1302319"][USER=1301175]2. I found that measuring seating pressure was just as easy by feel using a standard arbor press.[/QUOTE]Where reloading smartly, it is easy enough to feel a difference & which way. But that's not a [I]measure[/I].
The same can be said of primer seating (feel & measurement).

[QUOTE="David Christian, post: 37561768, member: 1302319"][USER=1301175]3. Once my case necks were dialed in (interference fit, neck hardness, and surface condition of the inside case neck and bullet surface) I saw and felt no difference in seating force.[/QUOTE]This is what I see as well.

There are other/different situations for seating forces meanings. From fully annealed partial sizing to FL sizing of hardened necks is a pretty big spread. Seating into donuts or neck shoulder junction can lead to wild measurements. Feel is of little use for these situations.[/user][/user]

 

[WIB3]

The 21st Century press is a good unit. I modified mine by removing the 100lb gauge and replaced it with a 0-15 digital. I sort my record rounds based on seating pressure. I try to get all 10 to be with in 1lb. Don’t have any scientific data to back it up but it has been working for me.

 

[243BR]

No disrespect meant to anyone who measures seating force, I know several GREAT shooters who swear by it.
I do have a question / comment though. If my understanding is correct most seating force measurements are around 20 - 30 psi. Aren't we "hitting it" with 40,000 to 50,000 psi when the powder goes off? That's a ratio of 1800 / 1(+ or -). I understand the need to control all the variables that we can, but can a difference of 10 psi really make a difference?
If I don't understand this concept, if I'm not looking at the situation correctly, I would truly like someone to explain it to me.
Again no disrespect to the great shooters who take the time to measure seating force.

 

[JFrank]

@Mikemci, I used a K&M with force pack for a bit. 3 observations. 1. I found no correlation between seating force and the impact on target or speed of the bullet. 2. I found that measuring seating pressure was just as easy by feel using a standard arbor press. 3. Once my case necks were dialed in (interference fit, neck hardness, and surface condition of the inside case neck and bullet surface) I saw and felt no difference in seating force.

On your 1st observation of no correlation between seating force and poi, at what distance did you record that observation?

 

[SealT5]

This is my experience and how I utilize my press

I own the KM with standard force pack. I use it only to sort and seg rounds that require more pressure then desired. A round that “pops” or takes excessive force to seat a bullets means I was inconsistent in my brass prep. Depending on the purpose for the loads I will usually set aside the outliers and use them as sighters, foulers, plinkers, etc...

I understand this is a piece of precision equipment that can serve a better purpose but for me it serves well.

Joe

 

[David Christian]

On your 1st observation of no correlation between seating force and poi, at what distance did you record that observation?

600 yards

 

[WIB3]

I have never tried it but just for fun I will load some 6mm’s using my normal bushing, than 5 more using one thousandth smaller. Obviously the ones with the smaller bushing will have more neck tension. I will chronograph all and post the results. Will also post the seating pressure on both groups. In benchrest competition repeatedly in muzzle velocity is whole game. Their are numerous factors that contribute to velocity.

 

[mikecr]

I understand the need to control all the variables that we can, but can a difference of 10 psi really make a difference?

You're overlooking the confinement attribute. Always remember; powder burn rate is directly tied to confinement.
Take a black powder musket, fire powder only, 'FOMP'. Reload with powder, roll a newspaper corner into a ball and gently push it down the bore to set on the powder (this is far less than 1PSI). On firing this barely confined powder, 'BOOM-YOW'. A 50cal bullet weighs far less than a pound.
If you were to confine the powder with an actual 30PSI barrier, that barrel would blow all to hell.

We are not pushing bullets through seating forces on firing. Our bullets are released with our cases (including necks) expanding. Force x Area, and bullets are fully free floating with but a ~billionth of an inch of neck expansion, so it doesn't take much.
But it also doesn't take much to vary pressure rate/peak with this, and we have a relatively narrow window that we're operating in.

Actual neck tension amounts to the force needed to overcome neck grip on bullets. On firing, this is purely neck spring back against an area of bullet bearing. Something we cannot currently measure..
Don't believe me?

Case #1
Take a fired & partially sized neck(say .125" in sizing length) to squeaky clean. Seat a squeaky clean bullet to a bearing depth of ~.200". Note the high seating force required in this.
Case #2
Same as #1 except dry coat both the necks and the bullet with WS2 (tungsten disulfide), which has an extremely low coefficient of friction, and does not affect powder burn. Note the low seating force required in this.
You can do it with as many as you like, and on firing -you will not see a difference between #1/#2.

Case #3
Same as #1 or #2, but this time size the neck ~.200" (same length as seated bullet bearing).
Now you've adjusted neck tension(increased it), and firing will show a higher MV.

Case #4
Same as any prior case. Partially size a neck with a bushing to cause ~1thou interference. This is ~2thou downsizing below cal, with ~1thou spring back outward, to ~1thou interference.
Seat a bullet, pull that bullet, and note that your neck springs back to that sized ~1thou interference.

Case #5
Same as #4 except use a bushing to cause way more downsizing (like 5thou interference).
Seat a bullet, pull that bullet, and note that your neck springs back to ~1thou interference.
There is no difference on firing of #4 or #5.
All that grips a bullet, w/resp to firing, is neck spring back, which exists within ~1thou of recovery.

 

[JFrank]

600 yards

Thank you,
I asked because I normally don’t see a bunch of poi difference with a slight seating force variation however awhile back I had that exact thing happen at 550 with a very light NT the group got BIG!

Note to self- don’t do that....

 

[dgeesaman]

If my understanding is correct most seating force measurements are around 20 - 30 psi. Aren't we "hitting it" with 40,000 to 50,000 psi when the powder goes off? That's a ratio of 1800 / 1(+ or -). I understand the need to control all the variables that we can, but can a difference of 10 psi really make a difference?
If I don't understand this concept, if I'm not looking at the situation correctly, I would truly like someone to explain it to me.

A basic notion is that seating force (neck tension) has a similar effect as seating length. The firing of a bullet is multiple stages of movement, and the timing of them is hard to measure but is critical. Consistent neck tension strongly influences this system and as such, consistency yields accuracy.

David

 

[ToddKS]

I have found that the depth of my case mouth chamfer has as much to do with my seating force as my bushing/mandrel selection. If my chamfer is not quite deep enough the seating force goes up considerably. The change in seating force in this case does not seem to affect my ES or SD. I had a batch of ammo recently that felt terrible seating the bullets but produced a singe digit ES and an SD in the high 2's which is better than my load normally performs.

 

[zipollini]

Couple of thoughts

1. If you jam your bullets neck tension and seating force don't make much difference. As David Tubb stated recently no need to anneal if jamming.

2. If you are trying to sort cases it is easier to use an expander mandrel after sizing and measuring the force or feel there instead at the time of bullet seating.

 

[Dusty Stevens]

1. If you jam your bullets neck tension and seating force don't make much difference. As David Tubb stated recently no need to anneal if jamming.

.

This is just like a carpet shower, “thats not right”