expander mandrel and donuts

[cj8vet]

I have been thinking about going the precision mandrel route to improve neck tension consistency(since I am not neck turning). My 284 shehane 6.5x284 lapua brass)does make donuts, my throat is long enough that they aren't an issue. BUT what will happen to the brass if I use the expander mandrels?
mark
cj8vet@gmail.com

 

[BoydAllen]

Even if the expander mandrel were to push all of the donut to the outside of the neck, I do not think that there would be a problem as long as the bullet's shank was not in that part of the neck. I can tell you that when I have re-turned necks that had developed donuts, that in order to be able to insert the turning mandrel just running an expander in and out was not enough. I had to leave it in for a bit. This happens because the thicker shoulder brass contributes to the spring back. (my guess)

 

[billlarson]

I would use a reamer to remove doughnuts...
Omho
Bill

 

[ronemus]

Expanding moves the donut to the outside of the neck where it's easy to turn. Inside reaming is difficult because you need to match the sized ID of the neck to the reamer diameter to cleanly remove the donut.

 

[Steve Jennings]

Expanding moves the donut to the outside of the neck where it's easy to turn. Inside reaming is difficult because you need to match the sized ID of the neck to the reamer diameter to cleanly remove the donut.

Consider that the donut is created/enhanced by full length sizing. How about using an expander pin to bring the top of the neck that actually grips the bullet to as fired size but stopping short of the donut. Wilson makes a reamer set up that easily removes all but a very small bit of the donut.

 

[Dave Marshall]

I was thinking a tapered expander mandrel where the full diameter is held short of the donut might work. It would be very tedious to set up for sure though. I think of like the reverse of keeping the full diameter of the bullet out of the donut.

 

[Scott Harris]

We have .240 FB with our Shehanes...bullet bearing surface sits well above the donut...no problems there. We run a carbide turning mandrel through the neck, past the donut to improve neck tension uniformity. Works very well for us and others using necked up 6.5-284 Lapua brass in no-turn 284s and Shehanes.

 

[cj8vet]

Scott,what diameter turning mandrel? Is this your last step? Source? mark

 

[mikecr]

what will happen to the brass if I use the expander mandrels?

It won't hurt anything.
I refer to neck expansion as pre-seating expansion. It drives thickness variance away from seating bullet bearing, and it establishes spring back bias as inward to grip bullets.
Other than improved control over that, mandrels also work better than sizing die expanders regarding runout.

 

[Uncle Ed]

I get the same approximate neck runout with my Forster full length die using its expander as I do if only using my Sinclair expander die. Meaning for me it is not worth sizing the case twice using the expander die when the Forster die can do it in one operation.

And if I neck turn I normally remove more brass just above the neck shoulder junction anyway. And any type expander will push neck thickness variations and donuts to the outside of the neck. And standard SAAMI chambers will give you room for a plain donut plus a frosted cream filled eclair with sprinkles.

Sinclair Expander Mandrel Die Test
https://www.longrangehunting.com/threads/sinclair-expander-mandrel-die-test.234793/

 

[mikecr]

Major flaw in that test Uncle Ed..
For one, his source of runout, which is high, is not neck expansion, but poor bullet seating. Expansion does not fix a poor seating effort, so of course there was no fixing of it there.

 

[Uncle Ed]

Major flaw in that test Uncle Ed..
For one, his source of runout, which is high, is not neck expansion, but poor bullet seating. Expansion does not fix a poor seating effort, so of course there was no fixing of it there.

There was .0002 bullet runout difference between using a expander die and a standard die with its expander in his test.
And all the bullets were seated with a standard Hornady seating die, so I would not say it was "poor bullet seating".
And I ran the same test using a Forster full length die and my Sinclair expander die using a Forster benchrest seating die and got very similar results.

mikecr, your the type person who would bitch if they hung you with a new rope.

 

[Brians356]

Expanding moves the donut to the outside of the neck where it's easy to turn.

Only if you could neck turn while it's still on the expander mandrel. After you pull the expander mandrel out, much of the donut will magically spring back inside of the neck. Most donuts are not worth the trouble, but the proper way to remove one is with a good reamer die.
-

 

[Rui]

Even if the expander mandrel were to push all of the donut to the outside of the neck, I do not think that there would be a problem as long as the bullet's shank was not in that part of the shank. I can tell you that when I have re-turned necks that had developed donuts, that in order to be able to insert the turning mandrel just running an expander in and out was not enough. I had to leave it in for a bit. This happens because the thicker shoulder brass contributes to the spring back. (my guess)

hi guys, I shoot a 7mmrsaum and have the same problem in using a expander mandrel.the brass spings back a lot, what I do now is annealing first then button than sizing and that cured my problem

 

[Texas10]

You've inspired me with this question about neck tension. And I think I'll try modifying what is working well for me and perhaps make it work even better.

I use a Lee collet die to neck size my 223 brass. I get really good, almost zero runout, and decent neck tension consistency. However, it could be better.

The Lee die squeezes the case neck against a mandrel, and perhaps by changing the diameter of that mandrel according to brass springback, I may be able to better control neck tension. Combine that with regular annealing every 3rd or 4th cycle.

As set of 4 or 5 pin gages to measure springback in the neck diameter, then changing die mandrel to get desired diameter after sizing. Just might could work.

 

[mike06]

You've inspired me with this question about neck tension. And I think I'll try modifying what is working well for me and perhaps make it work even better.

I use a Lee collet die to neck size my 223 brass. I get really good, almost zero runout, and decent neck tension consistency. However, it could be better.

The Lee die squeezes the case neck against a mandrel, and perhaps by changing the diameter of that mandrel according to brass springback, I may be able to better control neck tension. Combine that with regular annealing every 3rd or 4th cycle.

As set of 4 or 5 pin gages to measure springback in the neck diameter, then changing die mandrel to get desired diameter after sizing. Just might could work.

Just bought pins for my .223 from this company make sure you use the Florida Stock menu. Fast shipping cheap freight. https://www.suncoasttools.com/

 

[cj8vet]

Mike06, dumb question do we want go or no go? I’m guessing you bought 223 222 221 220
Thanks mark

 

[mike06]

I got the Vermont Gage Class ZZ minus pins. .222, .2225, .223, .2235, .224 and .2245 . I got six pins but likely I will end up only using one or two depending on the amount of spring back I get. I try for .0015 tension in my bolt rifles and .0025 to .003 mag in my AR15.