Neck expander mandrels

A

akinswi

New member
I currently have a lyman m die that I use to expand the necks on my cases. The expander mandrel is at .3065 when I expand the neck it springs back to .307 Any one know that if 21st or Sinclairs mandrels will fit in the thread of the lyman m die. I checked lymans website I couldn’t find a different mandrel they use a standard 30r mandrel which Im assuming is a universal 30 cal .3065 dia

I want to get a .306 and .3055 and experiment with them to increase the neck tension a bit for my service rifle loads. My neck OD after using 168 SMK in a 30-06 case is at .335

Trying to get the Neck OD down to at least .334 or .3335

Thanks
 
The mandrels are often made for outside neck turning. There are special die bodies that adapt them for use on a press. I don't think they are compatible with anything else. Both Sinclair and 21st Century sell mandrel die bodies.
 
If I understand you right,you can buy .3065 mandrels? I'd think you could spin it in a lathe or drill press and use a very fine (1200 grit or so) polishing stone to take off .0005 or .001
 
Nick,

https://21stcenturyinnovation.com/buy-online/ols/products/caliber-specific-expander-mandrel/v/E306

I was thinking of getting a .308 and .306 I would use the .308 first to basically flare the case mouth just a bit. then set the neck tension with the .306 mandrel.

HBiC

I do not have a lathe or drill press so I couldn’t evenly polish my lyman mandrel even tho that mandrel has the raised step to flare the case mouth just a bit which I like because even with boatail bullets that little step really helps center the bullet in the case neck

I could buy a cheap lathe from harbor freight, think it cost as much as the 21st body die not including the mandrels.
 
The steel mandrels will be hardened, so you might need a toolpost grinder to reduce them on a lathe. The nitrided ones will have their surface finish spoiled by material removal and should not be considered reworkable for size. The carbide ones would require diamond grinding points and lapping compounds to reduce and some skill working with carbide. I think, if you want to turn a custom size, you will want to start with drill rod and quench it and temper it yourself.

If you are trying to create an M-die type profile, the. 308” won't widen the top enough. Spring-back after expanding will make the opening narrower than the mandrel. You would need something closer to .3095" if you expect the bullet to slip into that portion of it. They have a 309", I see, so I would start with that, though if your brass hardens, you may need to anneal to make it work.

Another whole approach, since you have the M-die, would be to call Lyman and see if they will make you a set that has the same large step diameter, but narrows to your desired smaller diameter(s). It is still expanding by plunging down like the mandrels, but I don't know how the cost for the custom work will compare.
 
Contacting Lyman would save me from buying the die body and mandrels from 21st, which In my case I would have too buy two one for each mandrel.

I do have two lyman m dies one is in my first stage of my Dillion, 2nd I bought for the coax , I could chuck the mandrel in a power drill in my vise and put a piece of blue painters tape to mark where the larger step begins and polish from there. If I mess up just will order a new mandrel.

Its either this or I will have too get a neck bushing die which im trying to avoid
 
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