MANDREL DECISIONS

[Turpentine21]

I'm doubting so-so but hopefully by Tuesday I'll be in better shape after having a neck procedure on c3 thru c6 to take care of the 25 years of chronic pain. Temp wise it's been blazing pf mostly 100°+. I forgot about bushings and not using mandrels as that might be a better way to go?

This is my next test plan for the upcoming winter. It's to doggone hot to test now. But I'd like to go up slightly more on bushing size and see if I get the accuracy and consistency I have found with the bushing and mandrel. This year has been a rush to get this 6mm AR shooting accurately. Not so much time to work out the minutia.

 

[Turpentine21]

MAN, THAT WAS LOTS OF WORK ON YOUR END FOR REPAIRS! 11 years ago i has 4 fusions done in the front of my neck where my throat was pulled out of the way for it. dr said me voice box was really big. what'll be done mon and tue is a rfa (radio frequency ablation) where they burn/singe the nerves to keep the pain signals from reaching the brain. supposedly it can repair itself in 6 months to 6 years? a person on another forum had this done in the "L" section but only lasted 3.5 months on part of it and 5 months for the longest. so much for 6months to 6 years. if it works at all and gives me a month i'll be appreciative, but hope it last longer and not have to repeat it in a short time. my injuries was from 2 car accidents where i almost went thru the windshield on 1 and went upside down (didn't roll) in a convertible (soft top was on) w/o a seatbelt. not wearing the seatbelt saved my live as the driver's side was layed flat/flattened.


would a bushing be better than the mandrel?

I have had the RFA procedure after my first back surgery. L4-5, L5-S1. Where the doctor shaved the disc bulges, did a laminectomy but did no stabilization. Six weeks later I couldn't even walk with a walker. The Doctor evidently thought I was a drug seeker, or pansy, or knew things were beyond his intelligence level so he threw me on the pain management train. The RFA treatment along with a lot of other treatments, epidurals, did not work so my very honest Pain Management Dr. told me all we can do is give you pain meds to keep you comfortable. That things were too far gone, You need to find a good surgeon that can ID the issue and fix it. An orthopedic surgeon figured out that due to the reduced disc height my facet joints were rubbing against each other, bone on bone. Three months after the fusion I was back at work, minus the pain meds. Then two years later I fell while hanging a bow stand. That really started the roller coaster. But I survived, and can walk. To this day a good portion of that old l4-5,5-s1 fusion is still in there. Encased in bone where the doctors just decided to stop trying to get that hardware out. The T10-s2 fusion runs right over the top of it.. That doctor gal at Emery knew what she was doing!
But you never know, some of that PM stuff can help. Another friend is benefiting from it right now! I firmly still believe there are many things about the spine that doctors still don't know! But some know a lot more than others!
I'll be Praying for You.

 

[Nomosendero]

21st Century Innovation has .375 caliber mandrels. I recently asked them.

Thanks

 

[Okanogan]

I've been using Short Action Customs decapping mandrel for 3+ years on what I consider to be my precision rifles. The die, neck/shoulder bushing and mandrel combination is not cheap so I usually wait and pick up what I want during their annual Black Friday sale. I started using them because I sometimes felt noticeable difference in seating pressure just using Redding bushing dies. I notice less of a difference with the mandrels but could not quantitatively show that it makes any difference on my targets. I look at it similar to using a Auto Trickler with a FX-120i; it might not be necessary but it is one less variable to worry about.

 

[nube2.0]

Bushings size your brass from the outside
Mandrels size it from the inside
Mandrels should more consistent for achieving the desirable inside neck diameter
Both will have issues with inconsistencies in neck thickness

 

[ARlife4me]

I have had the RFA procedure after my first back surgery. L4-5, L5-S1. Where the doctor shaved the disc bulges, did a laminectomy but did no stabilization. Six weeks later I couldn't even walk with a walker. The Doctor evidently thought I was a drug seeker, or pansy, or knew things were beyond his intelligence level so he threw me on the pain management train. The RFA treatment along with a lot of other treatments, epidurals, did not work so my very honest Pain Management Dr. told me all we can do is give you pain meds to keep you comfortable. That things were too far gone, You need to find a good surgeon that can ID the issue and fix it. An orthopedic surgeon figured out that due to the reduced disc height my facet joints were rubbing against each other, bone on bone. Three months after the fusion I was back at work, minus the pain meds. Then two years later I fell while hanging a bow stand. That really started the roller coaster. But I survived, and can walk. To this day a good portion of that old l4-5,5-s1 fusion is still in there. Encased in bone where the doctors just decided to stop trying to get that hardware out. The T10-s2 fusion runs right over the top of it.. That doctor gal at Emery knew what she was doing!
But you never know, some of that PM stuff can help. Another friend is benefiting from it right now! I firmly still believe there are many things about the spine that doctors still don't know! But some know a lot more than others!
I'll be Praying for You.

I really don't want meds for a fix, I want my neck to be fixed long term! This last dr went into more depth to find exactly where and the cause of the issue. Hoping he's correct as i know the area that's being worked on is where the issues are. He wanted to check and see if it was the nerves or the bones causing the issue. From testing it was the nerves.

Thanks for the prayers as all is appreciated!

I feel sorry for those that are in worse pain than I and think I'm lucky enough to not be like them

 

[Mikecr]

During yielding, tension increases from far less -all the way to loss. So there is that, but there is bad, and nothing 'good' with all that change to brass.
In contrast, you could size necks to accept bullets with 1/2thou interference.
Then, there is no upsizing on seating. Just desired tension provided by full springback for a chosen bearing length, with way less working of brass.

By default, my perspectives are locked into what I do. MY plan.
That's too limited here, and not helpful for those with a different plan.
So let me argue with myself:

If it's in your plan to process anneal,, every reload,, perfectly,, then taking brass into yielding CAN work (maybe even better) to bring about consistent tension. This, because a yielding region of brass change reaches a potentially useful plateau.
But, only with absolutely perfect, constant, annealing (i.e. AMP induction, or salt bath dip).
A chart so that you can picture it:

I've always been the 1/2thou interference guy, adjusting tension with neck sizing length.
Among the advantages with this is that I don't have to bother with annealing beyond 1st formings.
I'm relying purely on minimal sizing to prevent work hardening.
Hell, I run one fitted chamber where I never even neck size. I don't have to, as fired necks spring back to original ~1/2thou interference.
With that, neck tension will never change, with no effort other than the beginning plan.
Anyway, since I am probably weird, I should at least speculate about how others are doing well in an opposite direction of mine.

On mandrels. I was actually the 1st guy who advocated to the masses, mandrel use for pre-seating expansion.
This was probably 30yrs ago, and what a ~10yr battle that was... Nobody would hear me.
I've actually used mandrels since 1975, when I learned in HS reloading class, that neck turning/expanding mandrels worked really well for this.
They greatly reduced loaded ammo runout at the time, and didn't seem to hurt anything otherwise.
I've used K&M and Sinclair (made by PMA Tool), and PMA customs. I love Sinclair's latest mandrel die system.

With a couple cartridges I've used an expander mandrel at cal (bullet diameter).
So I bushing down-size to ~1thou interference, and pre-seat expand the neck at cal.
This provides as much as I'll get, being a `1/2thou interference guy.
My mandrel die is instrumented to provide seating force of the mandrel. With necks well normalized in friction, this gives me opportunity to address/match neck tension -before seating any bullets.

 

[Turpentine21]

I really don't want meds for a fix, I want my neck to be fixed long term! This last dr went into more depth to find exactly where and the cause of the issue. Hoping he's correct as i know the area that's being worked on is where the issues are. He wanted to check and see if it was the nerves or the bones causing the issue. From testing it was the nerves.

Thanks for the prayers as all is appreciated!

I feel sorry for those that are in worse pain than I and think I'm lucky enough to not be like them

I did not want meds to fix my problem either. I'm better off than I ever thought I'd be again. Sounds like you have the right doctor. Chronic pain is tough mentally and physically. I hope things work well for you. 25 years is a long time.

 

[dstancu]

What you're referring to is an implied interference fit, which goes to zero, when you up-size with bullet seating.
That's not what tension is.
Tension is a force, and forces are not displacements.

Consider a neck with a bullet seated in it. What grips (tries to squeeze) the bullet?
You might have noticed at some point that pulling a seated bullet leaves the neck sprung back to ~1/2thou under cal, and not whatever your sized interference was. So the force that gripped that bullet existed in only that ~1/2thou of springback.
That springback force (hoop force in this case) was applied to an area of bullet bearing, to provide some amount of total grip.

We know springback force is tied to brass hardness, and thickness at a given hardness.
Aside from that, what is squeezing your seated bullet?
Answer: the AREA that springback force is applied.

So if you can set your neck brass hardness, and thickness, to consistency (at any tested best values), how can you adjust neck grip/tension?
Answer: AREA applied
Tension is easiest adjusted (IMO) through neck sizing LENGTH.
10 PSI springback against .25" bullet bearing length = 2.5 lbf tension
Against .125 bearing = 1.25 lbf tension

Then what about interference?
Your brass springback represents it's elasticity. Anything beyond the ~1/2thou springback in this case is yielding(sizing). And with that, the brass can't fully recover, but accepts your sizing. During yielding, tension increases from far less -all the way to loss. So there is that, but there is bad, and nothing 'good' with all that change to brass.
In contrast, you could size necks to accept bullets with 1/2thou interference.
Then, there is no upsizing on seating. Just desired tension provided by full springback for a chosen bearing length, with way less working of brass.

If you want to tweak neck tension, maybe just to see what effect it provides, you might try adjusting neck sizing length.
Next time you load develop, you might begin with lower interference, and half a sized neck.
Assume that excess brass sizing is not the best approach, and see how that works.

Thanks Mikecr for the detailed description of the interference fit, colloquially called "neck tension".
You make a very interesting point about the spring-back and the contact surface.

Brass spring-back is obviously what holds the bullet tight in place. It can also be referred to as the "Normal" (N) force, perpendicular on the contact surface. I see the bullet pretension as an expression of the static friction force. In order for the bullet to move along the neck, it has to be pushed longitudinally by a force equal or larger than the value calculated for the static friction:

Fmax=μs⋅N, where μs is the coefficient of static friction and N is the normal force.

However, as illustrated by the above formula, the maximum static friction force depends only on the normal force and the coefficient of static friction, not on the apparent contact area. That is because real contact occurs only at microscopic asperities whose total area scales with load (constriction amount) rather than with the nominal surface size. In other words, the more load (tighter), the closer the two surfaces get together, and the more microscopic contact for the same contact area.
From this, we can infer that the quality of the surface inside of the neck plays a major role, because it directly influences the static friction coefficient. That is why an even, smooth surface of the neck inside obtained through brushing and mandrel use creates a better, uniform, and repeatable contact with the bullet (higher μs).
That inside surface of the neck has a direct influence on the bullet alignment. The outside of the neck does not really touch the chamber before the expansion generated by the burn of the propellant.

Mikecr, do you happen to have measurements of the neck inside diameter from bullets pulled, for different interference fits? If that is always 1/2 thousands, regardless of the "neck tension" created during brass prep, that could lead to interesting conclusions...
For instance, from my empiric observations when reseating pulled bullets without any other resizing, I did not notice any significant change in muzzle velocity, SD, or accuracy on target.

 

[Mikecr]

from my empiric observations when reseating pulled bullets without any other resizing, I did not notice any significant change in muzzle velocity, SD, or accuracy on target.

Re-seating bullets makes no difference for me either.
But then I don't seat into much interference to begin with.
The ~1/2thou springback is approximate. Changes with neck thickness, hardness, and cal.
To calculate the grip force is really a hoop tension calc.
I've been meaning to put a spreadsheet together for this, but it isn't so beneficial to me.

I find that friction plays no role in bullet release. I run coated and uncoated bullets, with no MV difference.
This makes sense actually. Think about it; once a neck has expanded barely 0.0000000000001" the bullet is fully swinging in the wind.
It takes far less pressure to expand a neck so little, than to overcome friction.
It's amazing that it matters at all,, but it does.

On a side note;
People think they need 2-3thou neck clearance, or pressure rises. This is not true.

 

[bamban]

For folks who do neck expansion, you can take tuning to a much smaller increment using gauge pins, this is another option.

Mandrel Dies – Porter's Precision Products

portersprecisionproducts.com

 

[dstancu]

Re-seating bullets makes no difference for me either.
But then I don't seat into much interference to begin with.
The ~1/2thou springback is approximate. Changes with neck thickness, hardness, and cal.
To calculate the grip force is really a hoop tension calc.
I've been meaning to put a spreadsheet together for this, but it isn't so beneficial to me.

I find that friction plays no role in bullet release. I run coated and uncoated bullets, with no MV difference.
This makes sense actually. Think about it; once a neck has expanded barely 0.0000000000001" the bullet is fully swinging in the wind.
It takes far less pressure to expand a neck so little, than to overcome friction.
It's amazing that it matters at all,, but it does.

On a side note;
People think they need 2-3thou neck clearance, or pressure rises. This is not true.

Good point.
I assume some people prefer higher clearance simply trying to avoid the bullet being either pushed down in the case neck (e.g. by tight fitting ammo cases), or hung in the barrel throat when unloading a cartridge if loaded long, touching the grooves (it happened to me )...
I use mandrels with 2 thousands less than the bullet for all cartridges, mostly for consistency/simplification.
I think that is the only role played by increased static friction. When the gun goes boom, the force pushing the bullet out is immensely higher than the friction opposing the movement, not to mention the neck expansion in microseconds, as you said. Even in a case with only the primer and the bullet seated (no propellant), the primer detonation is enough to push the bullet out of the case (and stuck in the grooves).

 

[Phil Rizzo]

go to the short action customs site and use the calculator. it will tell you what bushing and mandrel to use based on the info you provide. https://shortactioncustoms.com/product/300-winchester-magnum-neck-shoulder-bushings/

SAC is top notch as noted.
Their seaters are not only precise but pretty dang versatile within cartridge families.

 

[Bitteroot]

I've tested a lot of different bushing sizes over the last decade, I don't use mandrels rather just size one direction.
Here's my question; Why do guys feel the need to calculate or consider spring back when choosing a bushing or mandrel when they have target results to follow ?