Comments on: Neck-Expander Mandrels for More Uniform Neck Tension

By: VF

VF — Thu, 13 Feb 2020 03:55:35 +0000

This is a tad off subject. On a magnum cartridge with a muzzle brake on rifle, how many thousandths of neck tension will prevent shifting of bullets in magazine from recoil?
Should I crimp or is a tighter inside neck diameter
sufficient? This would help in order to buy proper
mandrel sizes. Thanks

By: Julio

Julio — Fri, 27 Sep 2013 18:53:27 +0000

Thanks for the explanation. So we’re talking about hand-loading, not re-loading here. I’m good with that. Especially if those with unwanted heaps of over-worked, sub-prime, once-fired Lapua brass cluttering up their loading benches would like to clear the decks in my direction! (.308, 6.5CM, .243, .223 or .222 only please!)

By: Julio

Julio — Fri, 27 Sep 2013 06:04:45 +0000

“using a die with an expander ball will work the necks more — since you first size them down, then the ball expands them up again”. OK, maybe, but isn’t the degree to which the brass is worked the same whether you run a ball or a mandrel through the necks? It is still sized down by the die and up by the ball/mandrel. Also, why exactly would a mandrel give more consistent neck tension than an expander ball? I guess I’m missing something…

Editor: With many full-length sizing dies (unless they have been honed to a larger-than-standard neck diameter), you are reducing the neck diameter well below the diameter “out of the box”. Then you have to push it back out with the expander ball. Here we are talking about expanding new brass.

By: Mike

Mike — Thu, 26 Sep 2013 22:04:05 +0000

The bottom line is last sizing of necks is expansion, either with a mandrel or bullets, and bullets make terrible expanders.

By: Dennis Brown

Dennis Brown — Wed, 27 Jun 2012 18:43:54 +0000

I agree that these expanders made the process of seating bullets go much more smoothly. It also reduced runout from offset setting.

By: Tony Chow

Tony Chow — Tue, 12 Jun 2012 22:11:09 +0000

I only use the mandrel on new brass. My reason has less to do with concentricity, than fact that new case mouths often are slightly dinged and not completely round. I chamfer all new cases to prevent shaving of jackets. To chamfer out-of-round case mouths would result in an uneven cut. Running the cases through the mandrels prepare the cases for chamfering.

By: mike

mike — Tue, 12 Jun 2012 22:10:53 +0000

Cole, where were you indicating on the loaded ammo?

By: cole roberts

cole roberts — Tue, 21 Feb 2012 10:01:00 +0000

I used the Sinclair Expander Mandrel on once fired .338 Lapua brass after sizing. Check loaded rounds on concentricity gauge. Loaded rounds WITHOUT using sinclair expander mandrel read from .000 to .002. Loaded rounds USING mandrel all read from .003 to .005 out of round.

By: Eric Kennard

Eric Kennard — Sun, 05 Sep 2010 02:01:38 +0000

I use one of these every time I load a piece of brass new or once fired. These are also the way to go for expanding your favorite 6.5 x .284 brass to a straight .284.

One tip, The end of the expander mandrel is fairly blunt and can catch the case rim. It is much better if you round the point a bit on a lathe or even chucked up in a drill.

By: Mikecr

Mikecr — Thu, 22 May 2008 15:58:33 +0000

These expanders can also reduce runout from offset seating.
Prior to bullet seating, expand the sized necks to force thickness variance outward. With the Sinclair system, the necks will springback fine, and will not be pulled out of center. This leaves plenty of tension, and bullets seated more centered. I do this, even with turned necks, to get improved seating.