MANDREL DECISIONS

[Turpentine21]

I use the 21st century die and mandrels in 6.5 and 6mm. I have no complaints. Then again I've used nothing else to compare to.

 

[ntsqd]

21st Century seem to have the biggest supply of mandrels in sizes by the .001 steps. Set up a excel program to determine what you want for neck tension. I don't know it the math part will go through.

For a compare and contrast, MSC has 22,432 different p/n's for the ZZ Minus gauge pins that the Porter Precision system uses. A lot of those are either too small or too big to be of any use in reloading, but that is still a LOT of options.

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www.mscdirect.com

 

[Phil Rizzo]

Correction: 21st Century mandrels are offered in .0005 steps for each caliber.

 

[Turpentine21]

Correction: 21st Century mandrels are offered in .0005 steps for each caliber.

You are correct Phil, as usual. . I just bought 3 of them. .2405, .2410, and .2415. Already had a .2400. The 2405 and 2410 don't let my bullets slip and shoot the best.

 

[Mike Matteson]

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.

INTERESTING! I'll to do some thinking about what you have said. I have use donut stile neck at time, and found or seem to work better in grouping of rounds. I haven't play with that in a long time, but I will have to cross that bridge again. Bushing die can and do create a donut effect in resizing the brass. That would create the amount of area that the tension is applied to bore size of the bullet.
I felt that setting tension was by I.D of neck, and O.D. of bore sizes of the bullet being used. The difference between the two. Spring back does come into play there also. I don't fully understand yet, but learning. I have a thick head at times. Butting it against the wall doesn't seem to help at times.
People say there nothing new here. Looks to me like they are not reading!

 

[Turpentine21]

INTERESTING! I'll to do some thinking about what you have said. I have use donut stile neck at time, and found or seem to work better in grouping of rounds. I haven't play with that in a long time, but I will have to cross that bridge again. Bushing die can and do create a donut effect in resizing the brass. That would create the amount of area that the tension is applied to bore size of the bullet.
I felt that setting tension was by I.D of neck, and O.D. of bore sizes of the bullet being used. The difference between the two. Spring back does come into play there also. I don't fully understand yet, but learning. I have a thick head at times. Butting it against the wall doesn't seem to help at times.
People say there nothing new here. Looks to me like they are not reading!

I read a lot! But my comprehension skills are compromised!

 

[Mike Matteson]

I read a lot! But my comprehension skills are compromised!

Mined is a little short too.

 

[ntsqd]

Hoop Stress is a fairly common Engineering consideration. If you work in designing pressure vessels of just about any type you work with that formula every day. Can calculate the resulting Normal Force by basically working it backwards. Not that it will do you much good in knowing that, UNLESS you know exactly what condition the brass is in from hardness testing etc.

Out of curiosity I looked them up. Current price on the 21st 0.2415" mandrel is $23.75, Porter's are $11.50 (already ground with lead-in taper) MSC's current price on a 0.2415-" gauge pin is $4.48 (DIY lead-in taper grinding required). Porter sells the pins by the .0005" increment with a "+" or a "-", so can buy a 0.2415+ pin or a 0.2415- pin, which is roughly like buying a 0.24155 pin or a 0.24150 pin.

It does cost more for the Porter expander body and the machining industry standard ER collet, but those are one-time purchases (unless you were shooting BR-A's and now you're moving to a Cheytac, but that's also true of 21st).

 

[Mike Matteson]

Hoop Stress is a fairly common Engineering consideration. If you work in designing pressure vessels of just about any type you work with that formula every day. Can calculate the resulting Normal Force by basically working it backwards. Not that it will do you much good in knowing that, UNLESS you know exactly what condition the brass is in from hardness testing etc.

Out of curiosity I looked them up. Current price on the 21st 0.2415" mandrel is $23.75, Porter's are $11.50 (already ground with lead-in taper) MSC's current price on a 0.2415-" gauge pin is $4.48 (DIY lead-in taper grinding required). Porter sells the pins by the .0005" increment with a "+" or a "-", so can buy a 0.2415+ pin or a 0.2415- pin, which is roughly like buying a 0.24155 pin or a 0.24150 pin.

It does cost more for the Porter expander body and the machining industry standard ER collet, but those are one-time purchases (unless you were shooting BR-A's and now you're moving to a Cheytac, but that's also true of 21st).

The cost is a lot different from 21st and others for sure. That why I built a program to get me what I felt was needed for a mandrel. I have a lot of extra sitting around, that I can't use do to wrong sizes. So be carefull in ordering mandrels from 21st. If possible it would be better to talk, to them over the phone than ordering over the net.
I use bullet bore size -.003" to set I.D. of neck. After that I use bushing dies to set the O.D. of the neck. To start off with I use a mandrel to set I.D. of neck. I cut all my case to a length. Them cut my necks to a thickness. After that I just use a bushing die that's set tension of whatever I feel works the best for my rifles. Only using a mandrel the very first time to expand the neck to whatever I.D. I am after. That also sets up my pliots or mandrels to fit in the neck of the cases. At that time I have pushed out any irregularity of the neck to the outside, I believe, so that takes away of problem inside the neck. So I think, but could be wrong.
So far I've been only able to use a .001" less the case neck is expanded too. They say .0005" but couldn't get the neck cutter to work. To tight.
Hopefully this make sence to you or others.

 

[Nomosendero]

I thought I knew how to handload and I guess I am lucky with the results I have achieved, but it appears I don't know jack sh!!3t!

 

[Alibiiv]

I'm posting mostly out of curiosity. All I've done for 42 years is fl size w/button on every reload.

I have been reloading a very long time also, and there is "always" something to learn every day. I full length resize leaving a .002-004 thousandths bump on the shoulder on annealed brass. When I FLR I leave the expander plug out. I then deprime the brass with a universal depriming die. From this operation I use a Sinclair mandrel die for setting the neck tension, and the next step after the mandrel die is to turn the necks to clean up any runout of the brass. I use the mandrel to remove the donut from the shoulder/case neck area.

 

[Mike Matteson]

I thought I knew how to handload and I guess I am lucky with the results I have achieved, but it appears I don't know jack sh!!3t!

Sometimes I wonder about that too. At the same time it's where you can develop your load and see how it does on the target. Lots of things to work with at the same time. Working toward that single hole on the target. With what I known now I do wonder how I hit the target at all.

 

[Bitteroot]

Sometime's it's just a matter of wanting to take a program to the next level and without saying there was anything wrong in the first place but there is certainly a next plateau with new challenges.
That may be what many find so attractive about the sport of precision shooting.

 

[bamban]

I FLR. Run a mandrel at - 0.001 from bullet diameter. Trim. Next steps are done on the lathe.

Turn down a mandrel insitu, +.001 above bullet diameter, with a step shoulder that would stop the case.

In the tailstock, chuck up the appropriate shell holder in the tail stock.

While the spindle not spinning, push the case into the mandrel. Ever so slightly pull back on tailstock to allow the brass head to freely spin. Turn lathe spindle and make the cut with the appropriate single point cutting tool into small section into the shoulder.

This method from my own experience produces the most even neck wall.the cutter cuts the brass that is interference fit over the mandrel. No clearance between a traditional turning mandrel and the brass ID required

Sacrifice a brass to get the correct thickness using a ball micrometer. Once finished with the batch and removed the turned mandrel, if you ever need to turn more necks, even of the caliber, Chuck up material and cut another mandrel.