Need help selecting 21st Century mandrel sizes

A

avastcosmicarena

Sergeant of the Hide
Full Member
Minuteman
Jul 23, 2018
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#1
So, I've read & watched a lot of videos about the benefits of switching over to using a mandrel die + mandrel for expanding the internals of the neck before bullet seating, and I want to get into this.

I want to start with .223 to get used to it, and later on, as long as I like how it works, I'll start doing it for 6mm also.

The problem? I'm not really sure which mandrels to buy.

I don't want to get into neck turning right now. I just want to use the mandrel prior to bullet seating to get the right amount of tension. However, I've seen some people recommend using the neck turning mandrels instead of the expander mandrels.

I've also seen that 21st Century offers precision mandrels that incrementally step up in size .0005" at a time so you can really get exactly the right tension you want

Caliber Specific Expander Mandrels

21st Century Shooting, Reloading products, Caliber Specific Expander Mandrels
www.xxicsi.com www.xxicsi.com

Here's a video about them:

Unfortunately, it looks they only offer these precision mandrels in stainless steel, whereas they offer the regular expander & turning mandrels in some more slick coatings (Black Nitride & Titanium Nitride).

So, these are my questions:
- Should I go with the precision mandrels instead so I can more precisely dial in tension?
- If so, I don't want to buy the entire set. If I were to select 3-4 of them, which would be the most ideal sizes to go with?
- Alternatively, it might be more important to just have a slicker finish and go with the regular mandrels. Maybe, I could get what I need just by going with the neck turning mandrel instead & also get it in Black Nitride or Titanium Nitride at the same time?
 
#2
I cant answer all your questions as i only have the neck turn arbor with titanium Nitride but i have found it works well for me using 6.5 creedmoor lapua brass. I get 2 thou neck tension after running the arbor down the neck after sizing with a bushing die. It has greatly increased the consistency of my seating pressures. Before that i gave the k&m expander mandrel a try but i was only getting half a thousandths of neck tension.
 
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#3
DrManhattan5160 said:
I cant answer all your questions as i only have the neck turn arbor with titanium Nitride but i have found it works well for me using 6.5 creedmoor lapua brass. I get 2 thou neck tension after running the arbor down the neck after sizing with a bushing die. It has greatly increased the consistency of my seating pressures. Before that i gave the k&m expander mandrel a try but i was only getting half a thousandths of neck tension.
Click to expand...

Thanks for the info. Do you have any problems with sticking with the TiN finish or does it work pretty well?
 
#6
avastcosmicarena said:
So, I've read & watched a lot of videos about the benefits of switching over to using a mandrel die + mandrel for expanding the internals of the neck before bullet seating, and I want to get into this.

I want to start with .223 to get used to it, and later on, as long as I like how it works, I'll start doing it for 6mm also.

The problem? I'm not really sure which mandrels to buy.

I don't want to get into neck turning right now. I just want to use the mandrel prior to bullet seating to get the right amount of tension. However, I've seen some people recommend using the neck turning mandrels instead of the expander mandrels.

I've also seen that 21st Century offers precision mandrels that incrementally step up in size .0005" at a time so you can really get exactly the right tension you want

Caliber Specific Expander Mandrels

21st Century Shooting, Reloading products, Caliber Specific Expander Mandrels
www.xxicsi.com www.xxicsi.com

Here's a video about them:

Unfortunately, it looks they only offer these precision mandrels in stainless steel, whereas they offer the regular expander & turning mandrels in some more slick coatings (Black Nitride & Titanium Nitride).

So, these are my questions:
- Should I go with the precision mandrels instead so I can more precisely dial in tension?
- If so, I don't want to buy the entire set. If I were to select 3-4 of them, which would be the most ideal sizes to go with?
- Alternatively, it might be more important to just have a slicker finish and go with the regular mandrels. Maybe, I could get what I need just by going with the neck turning mandrel instead & also get it in Black Nitride or Titanium Nitride at the same time?
Click to expand...


The "Turning" mandrel is .002" under the specific caliber and the "Expanding" mandrel is .001" under the specific caliber. Buy the size that is .001" larger than your desired final neck ID. Most shooter want .002" or .003" of neck interference. Personally I think the .0005" increments is unnecessary unless you are trying to dial out the runout in their turning lathe. I highly doubt you're going to see any appreciable difference in performance incrementally between .002" and .004" of neck interference. Your really don't need four different mandrels, pick one of the two and make sure your sizing die is at least .002" less than the mandrel.

ETA: Every coating and material of mandrel will still gaul brass unless you lubricate it. I have stainless, TiN, and carbide and they all get brass build up of you use them dry.
 
#7
Dthomas3523 said:
I would get the TIN turning and expanding arbor.

And .002 under and up to your caliber and all the .0005 in between
Click to expand...
This.
The TIN is worth it but I still use a tiny bit of lube.
I use .002 under which I believe is the standard expander for neck turning.
Plenty of neck tension even for gassers in 223.

Nice for getting new brass to a decent neck tension as well.
 
#8
So, what do you all think about the video from the F Class guy I posted in the original post? He seems to prefer much less neck tension than most people, though he does admit that he has friends who use more than he does and have no issues. Any thoughts?
 
#9
avastcosmicarena said:
So, what do you all think about the video from the F Class guy I posted in the original post? He seems to prefer much less neck tension than most people, though he does admit that he has friends who use more than he does and have no issues. Any thoughts?
Click to expand...

F class = dropping round in by hand and chambering in a controlled manner

PRS = running bolt faster with mag feed

Too little neck tension in prs style shooting, if the bullet makes contact with fees ramp or anything (even too much dirt or carbon) it can be pushed further into casing.

Same line of thinking with jamming lands in prs. If you have to extract that live round, there’s a chance of bullet pulling out.
 
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#10
I use the size the turning mandrels are as I settled on getting .002 tension and it being the best all around. Plus you'll drive yourself nuts trying to get everything to be the same with tiny custom increments.

After firing a round I'll bring the neck back down within .002 or so of the bullet size with a Redding bushing die. Then open it up slightly to the .002 tension via the turning mandrel as this process has proven to overall be more consistant than with a bushing alone.
 
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#11
Ok, so using a 223 Remington case for example you would use a .223 diameter mandrel after you resize.
This will typically bring the neck inside diameter to .222 as the brass will spring back some giving you .002 tension.
 
#13
Dthomas3523 said:
F class = dropping round in by hand and chambering in a controlled manner

PRS = running bolt faster with mag feed

Too little neck tension in prs style shooting, if the bullet makes contact with fees ramp or anything (even too much dirt or carbon) it can be pushed further into casing.

Same line of thinking with jamming lands in prs. If you have to extract that live round, there’s a chance of bullet pulling out.
Click to expand...
I have seen the bullet extraction happen on a PRS stage, shooter was out of commission for that stage
 
#15
The turning arbor will be .221 or .002 under. This is what I use in my setup after FL sizing to uniformly expand case necks. I have the Tin finish mandrels and have great results without having to lube. They also have a black nitride finish that is supposed to be even better. I have one on order for my 6mm but have not received it yet to give feedback.
Basically, with 21st arbors, the expanding or “E” is .001 under and the turning “T” is .002 under.
 
#17
Dthomas3523 said:
F class = dropping round in by hand and chambering in a controlled manner

PRS = running bolt faster with mag feed

Too little neck tension in prs style shooting, if the bullet makes contact with fees ramp or anything (even too much dirt or carbon) it can be pushed further into casing.

Same line of thinking with jamming lands in prs. If you have to extract that live round, there’s a chance of bullet pulling out.
Click to expand...
The pulling projectiles from a jam is a myth if you are running 2 thou neck tension. It only happens if you are running very little or no neck tension. I run a jam on both my prs rifles and I've extracted hundreds of rounds and never had one move let alone be pulled out
 
#18
McMillan said:
The pulling projectiles from a jam is a myth if you are running 2 thou neck tension. It only happens if you are running very little or no neck tension. I run a jam on both my prs rifles and I've extracted hundreds of rounds and never had one move let alone be pulled out
Click to expand...

Did you not read the scenario/watch the video in which he was asking about??
 
#20
If you use a Expander mandrel your case neck will be .002 under bullet diameter, if you use a Turning mandrel your case neck will be .003 under bullet diameter.
 
#25
Bought the Black Nitride turning arbor and die for it. Will test this out with .223 for a while before deciding whether or not I need any other arbors/mandrels or getting the same for 6mm.
 
#28
Just an FYI, I emailed 21st on actual sizes.

"Thanks for reaching out to us! Our Black Nitride mandrels and arbors generally add .0002 to the raw stainless material. The 6.5 Expander is .2632, while the arbor is .2622. The 30 Cal expander is .3072 while the arbor is .3062. Int he past our mandrels/arbors had no issue in the sinclair body, but as of late there have been some fitting issues. I would suggest you use our body just to be sure."
 
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