Cleaning inside of case necks

[mikecr]

decreases seating force to allow the same grip using a larger bushing

You're decreasing seating force by using a larger bushing.
Higher friction due to clean necks could allow bullets to stay put as held in a magazine through firing, but it has no affect to peak pressure.
Using a larger bushing does, as it reduces tension regardless of neck cleanliness.

Neck tension is important to tune and not simply a matter of being 'enough' to hold bullet seating.
Especially when seated off the lands, which I doubt qualifies to Neal jones' notions.

 

[in2deep]

I think that if you try the other method it will be more obvious especially if you use a hand seating die as you can readily feel the difference in resistance needed to seat the bullet and how the relationship of neck lube (or lack of) and bushing size clearly affect each other as the type and amount of lube necessarily changes the actual neck tension and can be compensated for with the neck bushing.

I am probably not using proper terminology here and adding confusion in some way but I think actual neck tension (not just the number on the bushing) and the force needed to unseat a bullet during firing are affected in a combination of factors above.

 

[mikecr]

I think you're confusing friction forces needed to hold a bullet in an unfired neck, with expansion forces that come into play to release a bullet on firing.
Whether the necks are clean, polished, lubed, sanded rough, or left alone, this friction doesn't effect the load or MV.

A neck only needs to expand .0001" to completely release a bullet, which is barely a sneeze worth of pressure to that much area. But it takes more pressure than this to move a bullet, given it's base area & mass.
So a neck expands to release a bullet, before the bullet moves.
So seating forces contributed to friction have no affect on the load.
And they don't.

Actual tension(contraction/expansion forces) provides the need for a little sneeze or a big sneeze to release a bullet, and that is plenty enough to affect tune with most load combinations.
Very low tension implied by Neil is great in that low tension means low tension variance. But it cannot be assumed to contribute to the best load. That has to be tested for, especially while best seating has been determined to be off the lands.
Also, actual tension is a matter of springback(contraction), and is very independent of seating friction, and even seating forces(due to oversizing).

But again, excess seating friction/forces can damage bullets and cause inconsistent seating depths.
So there is no reason to cause this, or to reduce neck tension, just to clean necks.

 

[in2deep]

Thanks for clarifying the terminology makes it much easier to discuss this issue. I think we agree on everything except the part about seating bullets in a clean neck:

"But again, excess seating friction/forces can damage bullets and cause inconsistent seating depths.
So there is no reason to cause this, or to reduce neck tension, just to clean necks."

The only way to say it is that it does not cause me excess seating friction/forces (actually the opposite since my gun prefers the larger bushing now) as tested by a hand seater for 1500 rounds and the seating depths checked carefully on a comparator also don't show deviation since the bullet stays put in a clean unlubed neck and the Jones seater does a great job in regard to uniformity. Using the larger bushing I believe causes less deformation for me for obvious reasons and concentricity has been excellent so far with 15 reloads on the brass.

This is all probably an anomaly as my rifle shoots best with the larger bushing that the clean necks allow and if I needed a smaller bushing than this whole deal may stink on rice like you say. Like most things in reloading this only pertains to one specific rifle and YMMV but my gun really shoots using this setup and consistantly holds waterline at distance with only my wind reading the limiting factor. Many ways to skin a cat.

 

[Peter N]

After reading the comments on being able to maintain more consistent seating depths with less neck tension I did some experimenting at the lading bench. I sized 20 Lapua 6BR cases .03 under loaded diameter and then another 20 cases .01 under loaded diamameter. I then seated Berger 107s in all 40 with a Wilson seater. Using the Sinclair hex gage I then measured all the base to ogive lengths and compared the two lots. (these are not compressed loads so compression was not a factor). I did confirm that that the lower tension necks had better loaded bullet depth consistency than the higher tension necks. Widest spread for .01 cases was about .015 and the .03 cases was over .025. I am now a believer.

 

[mikecr]

Peter, I hope you meant spreads of .0015, and .0025, as even these are very high variance.
My seating extreme spreads using Wilson dies & also measuring with the nut(like you), are well under 1thou.
But what gets me there, aside from discussed so far, is uniforming seating forces with a Sinclair expander die prior to charging & seating. This also reduces loaded runout as measured off bullet noses.

My particular expander die is modified with an integrated resistive loadcell. I've used it for years and have pretty much tested a bunch about seating forces with & without it(using a 'PressureTrace' instead).
I know that seating results are directly tied to seating forces which are directly tied to seating friction. Indirect influence is provided by the mating of ogive to seater plug angles, and tension provided by neck springback.
I also know that the carbon in them necks is our friend.

Your results are inline with my observations, but important is that it's logical (that it makes sense).
Do you understand what I've been saying about tension as a completely different matter?
If not, I've got another easy test for you to do that's quick & easy.

 

[Peter N]

Mike,

Thanks for correcting my math error. I will try running the Sinclair expander through the cases after neck sizing. Do you use any lube on the inside of the case or does the carbon left after brushing provide enough anti friction? Also, what about new cases? I just got 200 new Lapuas and will expand before first loading. What about lube?

Thanks...........Peter

 

[DennisH]

I have read this entire post:

So seating my bullets @ .002 neck tension is recommended or not?

If I undersand correctly, if I seat my bullets @ .001, when firing the round, the neck is going to expand first before the bullet moves providing the same pressure as if the neck tensions was .002 or .003, correct?

Using less neck tension causes "less" damage to your bullet when seating? Just make sure the bullet is tight enough in the brass to stay in place even when chambering the round?

I usually brush the inside of my necks with mica while prepping, is this recommended?

And if I understand correctly, you use an expander mandrel on your brass "after" sizing your brass to insure consistancy?

PS: I only use lube when expanding brass necks.

I ask these questions because I know when I am seating my bulltes, some take more force to seat than others, my seating pressure will vary, I don't have a guage, but I know when it takes more force to seat some vs others when reloading. This can only be caused by inside neck tension ???

 

[mikecr]

Peter, the carbon IS my lube on fired brass as it provides barrier between metals. On first firing you could use graphite or other common neck lubes to provide barrier.

So seating my bullets @ .002 neck tension is recommended or not?

Yes, 2hou is great.

If I undersand correctly, if I seat my bullets @ .001, when firing the round, the neck is going to expand first before the bullet moves providing the same pressure as if the neck tensions was .002 or .003, correct?

No, more or less tension means more or less of the pressure spike to cause bullet release. Tension affects the rate of spike, like bullet weight, and early resistance to bullet engraving(seating w/resp to lands).
What I was suggesting is that friction between the bullet and it's neck doesn't matter to a load, but has it's price with seating forces(which affects seating consistency).

Using less neck tension causes "less" damage to your bullet when seating? Just make sure the bullet is tight enough in the brass to stay in place even when chambering the round?
I usually brush the inside of my necks with mica while prepping, is this recommended?

Actual tension is limited to springback of the necks. You won't damage any bullets with tension. It is the interference fit, or sizing created by bullet seating(with it's friction) that in an extreme can damage bullets.
Bullets are not good neck expanders. They aren't hardened like expanders.
So it's best not to size your necks beyond useful. NEVER FL size necks, and there is nothing useful in leaving necks more than 3thou under cal for sized portion.
As far as magazine loading, you need only enough gripping tension & friction to hold correct seating through recoil. Don't go overbored slippery on bullet grip, which circles back to carbon as ideal.
With carbon present and minimal tension, there is usually sufficient grip to hold desired seating with handling/loading. With that minimal tension, seating is more accurate and tension variance is lower to affect a tune.
With necks the less you do, all the way around, the better. But of course, trim, chamfer the mouths, and set your clearances.

And if I understand correctly, you use an expander mandrel on your brass "after" sizing your brass to insure consistancy?

Yes, this is correct. Consistency in seating force, and to reduce loaded runout.
The expander is way harder than brass. So there is no value in lubing for neck sizing & expansion. Necks aren't going to wedge/stick like case bodies in a die, as neck sizing forces are very small.

 

[Will]

Place magnet inside either a baggie or wrap in saran / shrink wrap. that works for me when using my SS media and I bet it will work for steel wool.

 

[jlow]

So a neck expands to release a bullet, before the bullet moves.

This is very interesting to me, surely when the powder ignites, it does both things at the same time, one is the pressure is pushing the bullet out of the case and yes it is also expanding the case. The question is how does one know which comes first?

Let’s play some what ifs. For example, if there is no friction holding the bullet, then can one assume that the bullets move before the case neck expands? Seems reasonable since with no friction, the force required to push the bullet would be very low i.e. much lower than required to expand the case.

So with that established, then what will happen when the amount of force holding the bullet is very high, ignoring the obvious eventual explosion, one could see that if the amount of force required to move the bullet is higher than it takes to expand the case, then the case has to expand before the bullet can move.

So this leaves us the middle ground which is at what point is there enough tension on the bullet that it will not move until the case expands? Without knowing this, would it be reasonable to conclude it is impossible to figure out which comes first?

 

[BoydAllen]

One thing that I find interesting in these discussions is that some shooters seem to be driven to clean the inside of their necks to a spotless condition, despite ample evidence that the most accurate shooters at 1-200 yards do not. Also, if a particular powder bullet combination gives best accuracy with neck tension on the high end (.003) it is very likely that an arbor press type seating die will show the best results for ogive to case head consistency. Beyond that, having such a die that is a very close fit, especially in the neck, is important to maximizing concentricity if flat base bullets are being loaded. Being anal about some things can decrease accuracy. Beyond that, if you load very far ahead of when you shoot, spotless neck interiors are much more likely to cold weld to bullets. If you must load ahead, load long enough so that chambering is impractical, and reseat shortly before shooting.

One more observation...For my most accurate rifles, 6PPCs, shooting 133 and flat base bullets, seated longer than touch, neck tension affects accuracy. Too little, and groups enlarge, and even within the range of tensions that produce good accuracy, higher tension seems to improve aggs. IMO target speak louder than any theory.

 

[Peter N]

Boyd....Did I understand you to say that if a bullet is seated long so that it is jammed some amount into the lands, that neck tension is more critical than if that same bullet is jumped to some degree?

 

[BoydAllen]

No, that is not what I meant to say. I have not tested, since I generally don't jump, but if anything, I would think that neck tension would be more important jumping. Where ever you seat, I think that consistency, within the shots that form a group (hopefully) is important. If I feel differences in seating force, for target work, I segregate loaded rounds and shoot like with like.

 

[mikecr]

One of todays bulletins:
http://bulletin.accurateshooter.com/2012/02/forum-member-averages-1-677-for-six-targets-at-600-yards/
This fella understands what I'm talkin bout!

I'm absolutely sure that consistent tension matters more while jumping bullets.
With this, it's H20 capacity and neck expansion that sets the pressure peak rate.
When jammed I would think that neck tension plays a lesser role, and it's hard to get more consistent early powder burn than produced with jam.

IMO, jammed and fast powder(very high pressures) enable advantages of complete powder burn within short barrels. This advantage puts a lot of other factors in the shadows.
But it doesn't apply so universally with hunting or long range cartridges & heavy bullets.
They are as likely to shoot better with a jump.