What size mandrel to expand?

Beeckie

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I’m going to give expanding with mandrels a try. Do you guys recommend -0.001 or -0.002 in size. I anneal with an AMP before each loading and size with Redding type S bushing dies.
 

7mMike

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I size with a non bushing die, and use a mandrel 2 thousands under bullet diameter for setting neck tension. And I also anneal with a amp.
 
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CarlM

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Make sure you brush out the necks after using the AMP, it makes a big difference in seating. I use a bronze brush and I also use the 2 thousands mandrel.
 
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Saffer

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I’m going to give expanding with mandrels a try. Do you guys recommend -0.001 or -0.002 in size. I anneal with an AMP before each loading and size with Redding type S bushing dies.
Why not use the bushing die to set your neck tension? I only use a mandrel on new brass.
 
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MarinePMI

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The size used is also driven by the seating method (Wilson seating die vs. press mounted die).
 

Trek

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I am also using the Redding FL S die... I use a bushing to bring in the neck, and then expand out to desired .307 carbide mandrel (for my 308)... AMP anneal and use a nylon brush on a drill (3 passes)... so far so good.
 

Lunchbox27

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This. I size my necks down with a bushing .004 under loaded diameter and expand with the TiN arbor.
Bingo. You can use a bushing. I do, 4 thou under as well. I already have the bushing dies and bushings so thats what I run. Had I known how well the mandrel works I would have bought cheap hornady dies, no bushing, remove expander button and the run it in the mandrel after.

Using the mandrel in my prep cut my ES down on all calibers and provided smooth seating each time. The bushing work well on their own, but only the outside is controlled. The mandrel covers the inside.

Again, IMO, you really don’t need a bushing die set if you are going to run a mandrel. No neck turning either. Fuuck that.
 
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MarinePMI

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It was pretty damn early in the morning when you posted this, coffee? I do not get this, please expound.
Wilson inline seating dies require less neck tension to seat the bullet correctly (especially without damage). Most have to have around .001 neck tension, which either most FL factory dies, means expanding the necks is required.

Make sense? (And yes, it was early, and on my first cup of coffee).
 

Dthomas3523

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I have the 21st century sets. So I have them in .0005 increments.

I use pin gauges (for example a .241 for .002 with a 6mm). I’ll use whatever mandrel it takes to get the right fit with pin gauge.

For example, some brass I use a .242 and others I need a .2425 to get .002 tension. Different spring back can even happen over the course of the same brass’s life and needs a different mandrel.
 
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MarinePMI

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I have the 21st century sets. So I have them in .0005 increments.

I use pin gauges (for example a .241 for .002 with a 6mm). I’ll use whatever mandrel it takes to get the right fit with pin gauge.

For example, some brass I use a .242 and others I need a .2425 to get .002 tension. Different spring back can even happen over the course of the same brass’s life and needs a different mandrel.
Exactly. Hornady Valkyrie brass has been a real pain in the Wilson dies, while Federal hasn't. The differing neck thicknesses and spring back are very noticeable with the inline seater dies.
 

milanuk

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You may have to play a round a little with bushing size and mandrel size to get the results you want. Just running a mandrel that is 2 thou under nominal bullet size thru the neck as the last step (in sizing) may not get you where you want to be; the brass is going to 'spring back' some amount, depending on how small the F/L die originally squeezed it down, and the state of the neck (freshly annealed, or not).

Most neck turning setups that use a Sinclair style mandrel have an 'expander' mandrel that is 0.001" under nominal bullet diameter, and a 'turning' mandrel that is 0.002" under bullet diameter (so the expanded neck will fit over the mandrel when you go to turn necks). Even if you're not turning necks, you can use those two different sizes to your advantage as far as expanding the neck a little more, or a little less.

Also... some other brands - like K&M - use expander mandrels that are actual bullet diameter, and pilots for the neck turner that are 0.001" under size. Since that was the system I use, it took me the longest damn time to figure out WTF people were talking about when they gushed on and on about the wonders of expanding with a neck turning mandrel :rolleyes:;)

Nowadays though, K&M offers neck expander mandrels in 0.0005" increments (as do others) if you *really* want to get particular about it. Either way, I'd highly recommend spending a few $$$ on some pin gauges in 0.0005" increments above and below your 'target' neck ID. They're like $7-8 each, and well worth it.

My (current) setup for my 'match' .308 Win stuff uses a Forster NM die, with the neck honed to .333 (after years of using either a .333 or .334 bushing in a Redding Type 'S' F/L die, I figured I knew what size to go with ;) ) and a Sinclair carbide .30 cal 'turning' mandrel (measures .306)... which with freshly annealed Lapua Palma brass nets me a .305 neck ID. I test with a .305- pin gauge, which slips right in with a piston fit, and a .3055- gauge, which stops on the chamfer of the mouth (y)
 
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Milo 2.5

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As in not crunching the nose/ogive of the bullet while seating it with an inline seater die and arbor press.
You do know that inline seaters were made to be used with a rubber mallet? Arbor presses were not that common when they first came out.
 

MarinePMI

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You do know that inline seaters were made to be used with a rubber mallet? Arbor presses were not that common when they first came out.

Regardless, everyone uses arbor presses these days...and it shouldn't matter (unless I'm missing something).
 

TRyanOC

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Why not use the bushing die to set your neck tension? I only use a mandrel on new brass.
This is my process as well. I was wondering about the theory of sizing down with a bushing and then expanding back out with a mandrel. Seems like an unnecessary step.
 

Dthomas3523

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This is my process as well. I was wondering about the theory of sizing down with a bushing and then expanding back out with a mandrel. Seems like an unnecessary step.
If you’re looking to make the most perfect ammo you can, it’s going to be the most consistent way. Bullet interacts with the inside of the neck, mandrel makes the inside of the neck as perfect as we can get it.

Will just the bushing gets it close enough? Probably. Some are looking for better than close enough and some aren’t. The step is unnecessary to some and necessary to others.
 
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TRyanOC

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With good brass it can be unnecessary. But it also doesnt hurt.
Help me to understand, please. I use mandrel on virgin brass for desired neck tension and skim turn necks. Then FL size after every firing, bumping shoulders back .001-.002 using S bushing dies and neck size with bushing .001-.002 neck tension. To use your method, would I use a neck bushing that is .004ish and then mandrel size out to .001-.002 tension?
 

TRyanOC

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If you’re looking to make the most perfect ammo you can, it’s going to be the most consistent way. Bullet interacts with the inside of the neck, mandrel makes the inside of the neck as perfect as we can get it.

Will just the bushing gets it close enough? Probably. Some are looking for better than close enough and some aren’t. The step is unnecessary to some and necessary to others.
If .002 neck tension is desired, would you use a bushing that is .002 smaller than a loaded round, and then use a .002 mandrel on the next step? Or would you size smaller with bushing to say .004 smaller and then size out with .002 larger mandrel?
 

Dthomas3523

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Help me to understand, please. I use mandrel on virgin brass for desired neck tension and skim turn necks. Then FL size after every firing, bumping shoulders back .001-.002 using S bushing dies and neck size with bushing .001-.002 neck tension. To use your method, would I use a neck bushing that is .004ish and then mandrel size out to .001-.002 tension?
Are you sure every piece of brass is turned to the exact .001 or so? Also, over time, brass can move a bit.

When you use a bushing only, let’s say brass piece A has .013 neck thickness, and piece B has .0125.

With the same bushing used on both, one will have more/less tension, but the same OD of loaded neck.

With a mandrel, they will both have the same tension/ID but different OD.

The ID is much more important than the OD.
 

TRyanOC

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Are you sure every piece of brass is turned to the exact .001 or so? Also, over time, brass can move a bit.

When you use a bushing only, let’s say brass piece A has .013 neck thickness, and piece B has .0125.

With the same bushing used on both, one will have more/less tension, but the same OD of loaded neck.

With a mandrel, they will both have the same tension/ID but different OD.

The ID is much more important than the OD.
Thank you, this makes sense to me now.
 
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WhiskeyWebber

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I've added a few steps to my reloading lately. I have 60 rounds of 6xc made up where I've annealed for the first time, used an expander mandrel 0.002" under, and I'm also seating with 0.060" jump. This gun and my old process have always grouped at 0.6 to 0.7 MOA which I thought was definitely good enough. It will be interesting if this brings those groups down to .3/.4. Planning to test later this week.
 

Dthomas3523

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I've added a few steps to my reloading lately. I have 60 rounds of 6xc made up where I've annealed for the first time, used an expander mandrel 0.002" under, and I'm also seating with 0.060" jump. This gun and my old process have always grouped at 0.6 to 0.7 MOA which I thought was definitely good enough. It will be interesting if this brings those groups down to .3/.4. Planning to test later this week.
Keep in mind, when using a mandrel, brass springs back tighter. With a bushing it springs back looser.

I typically need to use a .001 under to get .002 due to sprinting back tighter. Your .002 under may be closer to .003 once it springs back.

This is why I use pin gauges to check my neck tension. Sometimes it’s not as easy as just using the exact number over or under what you want the final tension to be.
 
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Why not use the bushing die to set your neck tension? I only use a mandrel on new brass.
When you set the neck tension to .002” using a bushing the direction of spring back is away from the bullet. When you use a mandrel it is toward the bullet. The latter favors bullet retention.