Expanding vs Turning Mandrels

[Polaris_Doc]

Ok, so I want to start using mandrels to size the inside of my necks vs just using Redding type S dies. I've been noticing some inconsistencies in seating force and concentricity on loaded rounds. I anneal my brass after every firing with an AMP annealer. I use Redding TiN bushings that I may switch SAC after watching their bushings make nearly zero runout.
So should I use the turning mandrels that are .002 under bullet diameter, or the expanding ones that are .001 under? I'm assuming .003 under bushings, then the turning mandrels .002 under based on annealing and not as much spring back? Can I get some of the more knowledgeable guys than me on here to chime in? Thanks in advance.

 

[Mark M.]

I'm running my cases threw the Lee collet die then my expander mandrel die, I end up with .0015 tention and neck thickness is very consistent all around

 

[QuietTexan]

That's a perfectly good plan to start with for trying a mandrel. If you want to go deeper getting a pair of mics will help you narrow down on bushing size and mandrel size selection. I'm not sure you'll see much of a difference though just adding a mandrel, especially if you're using the sizing button that came with the die. If you aren't and are only using the bushing to size down, you might be able to see a difference.

For reducing seating pressure variations the other major factors are case necks thicknesses varying excessively, and how much of the neck you're sizing. You could try sizing less of the neck, or checking your brass for excessive thickness variations first before adding the new mandrel new step to the process.

Neck tension and max bullet grip force

Does anyone know how much spring back tension is possible with any given neck diameter and/or case wall thickness for holding a bullet? Brass will stretch at a certain point and no longer provide an increase in the spring back force that would increase bullet tension. At some point, I would...

www.longrangehunting.com

 

[lancetkenyon]

Try both. Use whatever works best for accuracy and ES after testing.

 

[Polaris_Doc]

That's a perfectly good plan to start with for trying a mandrel. If you want to go deeper getting a pair of mics will help you narrow down on bushing size and mandrel size selection. I'm not sure you'll see much of a difference though just adding a mandrel, especially if you're using the sizing button that came with the die. If you aren't and are only using the bushing to size down, you might be able to see a difference.

For reducing seating pressure variations the other major factors are case necks thicknesses varying excessively, and how much of the neck you're sizing. You could try sizing less of the neck, or checking your brass for excessive thickness variations first before adding the new mandrel new step to the process.

Neck tension and max bullet grip force

Does anyone know how much spring back tension is possible with any given neck diameter and/or case wall thickness for holding a bullet? Brass will stretch at a certain point and no longer provide an increase in the spring back force that would increase bullet tension. At some point, I would...

www.longrangehunting.com

Forgot to mention that, but yes, I am neck turning to eliminate high spots, and I use micrometers to get accurate measurements. But I figure unless I find someone with an auto-DOD that will charge a small fee to turn the inside and outside of the necks, then I'm hoping the mandrel after the bushing will hopefully push the discrepancies out versus the bushing pushing them in.
I have a v4 on the way, And I figured the last piece of the puzzle would be the would be the AMP Press. That would be probably the easiest way to eliminate flyers by culling the ones that are way off on seating force for the charts.

 

[WildRose]

If you aren't already doing so uniforming the necks by neck turning will be a really big help in getting consistent neck tension. No matter what you do as far as expanding the neck there's only so much room in the chamber and "out of round necks that are thicker in one area than others creates multiple issues including issues with concentricity.

As for which type, both have advantages/disadvantages pick one and as Lance said, check your results, if you're not happy, try the other.

 

[QuietTexan]

Well ok, different conversation time Seeing as how you're a fellow connoisseur of excessively excessive reloading equipment... (love my V4, I'm sure you will too)

What caliber are you doing this on? Smaller calibers have less tension to work with in general than larger. On my 6.5CM comp rifle I've been using -.002 bushing /+.001 mandrel -meaning the second mandrel up that actually opens the neck. My new pin gauges are in to try to get that measurement tighter.

You probably are trying to use the mandrels you have already, but take a look at the 21st Century or K+M mandrels - you can order in 0.0005" increments and really dial in on the best size instead of being limited to the -.002 or -.001 turning kit mandrels. Long term. Near term try both the turning mandrels and see if either makes a difference on a target versus the bushing you're using now.

I agree on the AMP press. I'm very much looking forward to comparing it to the K+M force pack.

 

[Polaris_Doc]

I'll have to check those out as I would agree .0005 increments would've nicer than 001. I actually don't have any mandrels right now and want to get the right thing the 1st time instead of having to buy twice.
Basically 20br, 243, 6br, 6gt, 6.5cm, 7saum, 30sm, 30br. And I'm sure as time goes on I will add to the list. Going to start with the 6gt and 6.5cm first.
I absolutely believe the AMP press would be the final piece of the puzzle, but I do not shoot f-class nor anything more competitive than PRS (for now) so I really can't justify that expense right now. After reading about all the testing and science that went behind the AMP annealer I was absolutely sold.

 

[QuietTexan]

Ah my bad, I thought you had the turning and expanding mandrels since you skim turned necks.

30BR might be the best place to start, since it should show the greatest impact of changes to neck sizing. I bought the caliber set from 21st Century for the 6.5mm, the cost kind of sucked but it's everything I needed to actually work on the process. I still use Sinclair's turning mandrels in 6mm until I get a better barrel spun up.

 

[Polaris_Doc]

Well, not sure how that one is gonna go for that testing. It is a 330 chamber, so the necks are turned to .010 for 328 loaded. Not much to work with and necks get pretty soft after annealing. Fun gun tho, and definitely turns dogs to soup!

 

[QuietTexan]

Haha fair enough, yeah maybe pick one you can move the brass a titch bit more. There was a thread recently where Alex Wheeler was talking about moving necks down 0.007" and getting good results, so pick whatever you have that's loose and start with it to see what happens maybe.

 

[Beluebow]

The 21st Century expander set that QuietTexan mentioned is good to go.

For a slightly cheaper option and still quality.

Mandrel Dies – Porter's Precision Products

www.portersprecisionproducts.com

 

[ntsqd]

I'll have to check those out as I would agree .0005 increments would've nicer than 001. I actually don't have any mandrels right now and want to get the right thing the 1st time instead of having to buy twice.
Basically 20br, 243, 6br, 6gt, 6.5cm, 7saum, 30sm, 30br. And I'm sure as time goes on I will add to the list. Going to start with the 6gt and 6.5cm first.
I absolutely believe the AMP press would be the final piece of the puzzle, but I do not shoot f-class nor anything more competitive than PRS (for now) so I really can't justify that expense right now. After reading about all the testing and science that went behind the AMP annealer I was absolutely sold.

If you haven't already purchased any expanding mandrel tools I'll suggest looking at the Porter's Precision system. It uses standard gauge pins for the mandrels and standard ER series machine tool collets and collet nuts. This way you're not tied to any particular mandrel mfg. and can buy the pins and collets from any machine shop supplier (MSC-Direct, Travers, & McMaster are easy online sources), and those come with a certification so that you know the pin is the size that it claims to be.

Mandrel Dies – Porter's Precision Products

www.portersprecisionproducts.com

 

[SteveBurton]

I started going down this rabbit hole myself so I'll share what I have found out so far. This applies to my factory Rem 700 SPS varmint in 308 Win that I use for PRS.
I'm using Lapua LRP brass. I don't neck turn because I know the necks are pretty consistent at 0.015.
I anneal after every firing.
I use a Redding FL bushing die with a 0.333 TiN bushing. This will size the necks down to an inside diameter of 0.303 which I have checked with pin gauges.
I use a 0.307 mandrel from PMA. It sizes the necks to 0.306 which I have also checked with pin gauges. I've loaded hundreds of rounds this way and every piece of brass I check is spot on.
My load gives me an ES of 9 and SD of 3 and I typically put 5 shots into .4 MOA

I'm very happy with the results so far but admit that I want to try some of the SAC bushings and the 21st Century mandrels. I just have a hard time justifying the expense when my process is working so well right now.
I used to neck turn and play with bushing sizes, neck size only, etc. I feel the mandrel is more consistent and the FL bushing die doesn't work the neck as much as a FL die does. One trick I do is leave the mandrel a little loose in the holder the same way you setup the bushings. I'm thinking it will align with the neck better and cause less runout. Does it really work that way? I have no idea but it makes me happy.