Neck sizing with mandrel

[kevins750]

Can someone explain the process?

Better than regular sizer in the die?

Is there a die with a mandrel sizer inside or do you
Purchase a mandrel sizer and install it in your die?

Sorry for the questions, and is it really needed for non comp shooting.

[pacrat]

Can someone explain the process?

Better than regular sizer in the die?

Is there a die with a mandrel sizer inside or do you
Purchase a mandrel sizer and install it in your die?

Sorry for the questions, and is it really needed for non comp shooting.

Standard sizing dies use friction to extrude the case smaller. And in the neck area, they size smaller than finish size. Then the "expander" that is part of the depriming pin, is pulled up out of the case to expand the neck to finish size.

Mandrel sizer is for neck sizing only. The mandrel fits inside the case, then as the ram goes up farther the fingers of a "collet" squeeze the case laterally to size the neck onto the mandrel.

You cannot simply put a mandrel in a standard sizing die. Because it doesn't have a collet.

Sizers that use a mandrel are commonly called a "collet die". Lee Precision makes excellent collet neck sizer dies.

https://leeprecision.com/reloading-dies/rifle-dies/lee-collet-dies

Best to get the Deluxe/Ultimate die set. It includes both a collet neck sizer and the standard Full Length sizer.

https://leeprecision.com/ultimate-rifle-die-set/

[longrange1]

pacrat explained the collet die....the other way is to neck size with a bushing and then run an expander mandrel into the neck to get the finial size in a separate step.

[LynnJr]

Kevin750
K-M sells what they call an Expandiron that is smooth and tapered. Generally it is used to prefit brass to a mandrel before neckturning but has become commonplace with shooters who don't anneal or don't seat into the lands.
On a bench type gun the necks only have a 0.001 of clearance so work hardening of the brass takes several firings.
On bench type guns the bullet is oftentimes seated into the lands giving very consistent ignition and low extreme spreads.
Consistency is what wins matches.

With other forms of shooting where magazines restrict the length of your loaded rounds and jumping bullets is the norm consistent neck tension is more critical to achieve top accuracy.
When you combine a bullet requiring jump and a loose chamber necks can work harden very quickly.
By using a mandrel your brass has less grip but a more uniform grip on the bullet which helps with shot to shot variation in neck tension and thus extreme spread.
The bigger the clearances get the more important it is to anneal.
The picture is if a couple mandrels that show how they thread into your press like a normal die.
You can use a graphite dry neck lube or Imperial sizing die wax for lubricant.
Factory brass has a hardness near 100. Once fired loose brass that has been sized for a factory type chamber can be 140 hardness and many times fired brass can approach 200.
If you shoot brass that us 100 with brass that is 150 you won't get a consistent release of the bullet and higher than normal extreme spreads.
If you seat hard into the lands the neck expands before the bullet begins down the barrel which helps your extreme spreads.
The mandrel is used to lessen the necks affect on releasing the bullet in a consistent pattern.