School me on 21st Century neck mandrel dies

pmclaine

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Nov 6, 2011
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#1
I'm about to tool up the S1050 to reload .308.

I'm intrigued by the idea of adding a neck mandrel die to my brass processing tool head.

Currently I decap and partial size in station one.

Swage in station two.

Come around to 2100 hrs and full length size/trim with a Dillon rapid trim.

The Dillon trim die is pretty tight on it's design. I currently push shoulders back about .002/.003 from fired brass.

I think the necks are probably tight on the Dillon trim die as evidenced by some "wasp waist" below the seat of the bullet.

If I run a 21st Century neck mandrel die after the trim die with a .307 mandrel am I on the right track to a better process?

My bullets are typically 168/175 SMK or Nosler CCs.

Thank you.
 

spife7980

Full Member
Feb 10, 2017
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#2
The .307 is the expander mandrel and the .306 is the turning mandrel, correct? I think you would want to use the turning mandrel.

At least that’s what I’m using, their titanium nitride whatever and it measures .306. I had always heard that you have to go above .001 for spring back but before buying I asked and the general consensus is that it turns out they don’t spring that much, they pretty much stay set at what diameter you open them with. And I’ve found that to be true this far. So the .306 turning mandrel will give you the default .002 of neck tension. If you developed with some other amount then you can get mandrels turned for whatever diameter.
 

fxdrider

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Jan 3, 2014
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#3
I recently bought one in 6.5 Creedmoor. The expander ball on my Redding FL sizer was leaving me with an enormous(I thought) amount of neck tension - .0035. It took a very deliberate effort to seat the bullet. With the mandrel, I'm getting .002, and the feel when seating is much smoother. I believe it's made a positive difference, though I can't absolutely prove it. I recently tried a previously 3/4-ish MOA load with the mandrel and the results were several sub-3/8 MOA groups. Did the mandrel make the difference? Possibly. But I also changed the stock at the same time. And the brass I used was once-fired rather than virgin. So it could be attributed to other factors. I don't think it hurts though.
I bought the expander mandrel.
 

pmclaine

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Nov 6, 2011
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#4
I run the ball on my first Dillon die which straightens any neck damage prior to going to the trim die but than I think the trim die "over sizes" the neck.

Im not using a bushing die or such so Im just looking for the mandrel die to hopefully homogenize things.

So if I read the above correctly I have one vote for the turning mandrel and one vote for the expander mandrel.....

My thought with going to .307 was that if my necks are .305 with spring back Id end up about .306. If history shows little spring back is limited and .306 works....

Ill probably buy both if the price is reasonable and have to use my calipers to figure it out.
 

fxdrider

Full Member
Jan 3, 2014
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#5
I run the ball on my first Dillon die which straightens any neck damage prior to going to the trim die but than I think the trim die "over sizes" the neck.

Im not using a bushing die or such so Im just looking for the mandrel die to hopefully homogenize things.

So if I read the above correctly I have one vote for the turning mandrel and one vote for the expander mandrel.....

My thought with going to .307 was that if my necks are .305 with spring back Id end up about .306. If history shows little spring back is limited and .306 works....

Ill probably buy both if the price is reasonable and have to use my calipers to figure it out.
You have to order the expander die body for $34.99 (currently) plus the mandrels - the titanium ones are $18.95 each. You only have to buy the body once, and then mandrels for any caliber you wish.

21st Century Shooting - Die Body

21st Century Shooting - Mandrels
 

padom

SuperMod
Staff member
Mar 13, 2013
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#6
I run the Dillon trim dies on my XL650 for 223, 308, 300blk and 6.5cm then 21st Century TiN "Turning" mandrels in the final step to set .002 neck tension. This provides extremely concentric ammo with virtually no runout.

My trim does create way too much neck tension if I didnt use the mandrel.
 
Jun 7, 2012
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#7
For bolt guns I use a Sinclair expanding mandrel .001 undersized, and for gas guns I use the turning mandrel .002 undersized.

The main benefit I've seen from the mandrel is with 260 Remington where it is the final sizing step because a sizing button can raise a little bur/donut at the neck shoulder junction.

Getting a Forster die honed to the right dimensions for your brass is another excellent idea.

Also do not overlook chamfering/deburing the case necks. I definitely notice when a bullet jacket catches on the burr of a case mouth.
 

pmclaine

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Nov 6, 2011
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#8
Good info you guys set me on the right path

Ill be trying out a TiN "turning" mandrel for my upcoming reload session.

I see in the video they set these up with the lock ring loose to allow float...is that pretty much how everyone runs them?

Agreed on the chamfer/debur. The Dillon cuts square and sharp. I can process thousands of cases through my press with little effort or time but chamfer/debur each case by hand blows but is necessary.

Does the mandrel perform any useful "swaging" of the Rapid Trim cut such that an SMK would slip right in?
 

fxdrider

Full Member
Jan 3, 2014
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#9
I see in the video they set these up with the lock ring loose to allow float...is that pretty much how everyone runs them?
I had mine set up with the locking ring slightly snugged up against the press. I didn't experience any negative effects. But they do recommend in their video (about 2:00 in) to leave it slightly loose. Try it both ways...load up 10 rounds of each. It'll either make a difference or it won't.
 

pmclaine

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#10
Ill do whichever needs to be done to prevent the mandrel from hitting the tops of the case necks and delaying the progressive operation.

It looks like the mandrel has a nice taper to allow it to find home like throwing a hot dog into the Callahan Tunnel so to speak.

It was not that way with the backer rod on the swage station of the Dillon until I took out the rod and tapered the tip to a more pointy appearance.

Im not a reloader that checks runout as evidenced by the fact Im reloading progressive....just looking for an easy way to make for a better quality ammo and I think uniforming my neck tension, relieving some of the excess tension created by the Trim die, will be about as far as I can bring it.
 
Likes: fxdrider

pmclaine

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Nov 6, 2011
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#12
I think I liked Sinclair better when they were a stand alone company.

They have some neat stuff. I think soon Brownells will just consume it.

Not that I have anything against Brownells but Sinclair was able to be more innovative.
 
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