Size of K&M Neck Expanding Mandrel for 6mm?

[RonAKA]

K&M say you have to use a mandrel to uniform the neck ID before neck turning. That makes sense. Trying to figure out if I need one or if my expander ball will leave the brass right size. Does anyone have an accurate measurement of the expander mandrel for a 6mm?

 

[duanepa]

Someone will get you the measurement. If I recall, there wasn't enough tension to hold a bullet after using their expander. So, I think you'll be a little tight.

 

[RonAKA]

Yes, I guess it will depend on the mandrel diameter they use on the cutter as well. So if someone has a K&M I would appreciate that dimension as well.

 

[CoverDog]

I did this to the best of my ability...The expander mandrel measured .2435 and the cutter measured .2425. I did not remover the cutter from the holder but got a good reading about 1/4" from the carbide cutters on the end.

 

[artbosco]

K&M say you have to use a mandrel to uniform the neck ID before neck turning. That makes sense. Trying to figure out if I need one or if my expander ball will leave the brass right size. Does anyone have an accurate measurement of the expander mandrel for a 6mm?

The K&M Expandiron's 6mm mandrel for uniforming the ID of brass to be turned on a K&M Neck Turner is the PERFECT size for matching up with the Turner's 6mm pilot.

I highly recommend the use of matched up mandrels and pilots for optimum results.

 

[RonAKA]

Thanks for the feedback and CoverDog for taking the time to measure your mandrels. Yes, it looks like I have little choice but to buy their expander to use their turner. I have a Forster "oversized" expander ball, but it is still only a full 0.243 and results in a 0.242" neck ID after springback. Looks like that would be 0.0003 to 0.0005" too tight. Fired cases are about 0.2430-0.2433 ID, and too large.

Are they the only ones that requires a special sizer for their turner?

 

[TonyR]

Ron.
You might want to consider a custom Wilson inside neck reamer the exact diameter of your turner mandrel/pilot instead of a different expander mandrel. The K&M carbide mandrels clean out the donut but do not clean up the inside of the neck as well. i found that my tube mic would give different readings after turning depending on where I measured. The inside neck reamer eliminated that variation. I have tried several neck turners and they all have had their own sizes for the pilots and expander mandrels. I went to the inside neck reamer when I went to the Hart neck turner which uses a plain steel mandrel without a cutter like the K&M carbide. I couldn't get my expanded 6.5X284 to 284 brass onto the turner mandrel/pilot because of the donut that formed from the expansion to .284 from 6.5mm despite using the correct diameter expander mandrel for the Hart turner. You also need to be careful putting the caseneck on and off those K&M carbide mandrel/cutters because they can score the inside of the neck. That is part of why I decided to try the Hart turner.

 

[artbosco]

Are they the only ones that requires a special sizer for their turner?

K&M and other companies don't require you to use a certain sizer or matching tools, however, experience shows you obtain the best results by doing so.

Each caliber has a corresponding K&M mandrel and pilot engineered to provide the requisite spacing for optimum turning.

See paragraph on The Expander a third of the way down this page: http://riflemansjournal.blogspot.com/2009/12/reloading-neck-turning.html

 

[Klong]

I have K&M as well as Sinclair neck turning setup. Too lazy to go measure them though.

What I will tell you is that after using the expander on all my Lapua brass I had to turn down the cutter mandrel. It is easy and worked great. The cutter mandrels where so tight, I could not keep cases in the shell holder. A brief polish on fine sanding cloth, and everything works as it should. I resize after neck turning so the actual expander size is of no concern to me.

 

[spclark]

After I received the K&M neck turning rig I'd ordered for .30 caliber, I found the mandrel to be too large to permit use with necks sized by my Sinclair E-30 expander. So I bought one of K&M's expander tools with the .30 mandrel.

Expanded & turned necks won't hold a bullet, so a pass into a neck bushing is needed before final case processing (cleaning) and priming.

I don't feel the K&M turning mandrel is too tight, I get no perceptible heating of case necks using a power drill @ ~ 30 - 45 rpm to turn cases. I use RCBS Case Lube:

http://www.midwayusa.com/viewproduct/?productnumber=479231

- for sizing as well as turning, both on the mandrels and on the cutter.

 

[artbosco]

You also need to be careful putting the case neck on and off those K&M carbide mandrel cutters because they can score the inside of the neck.

SUGGESTION!

When anyone attempts to do this please ensure your power tool [for example, a power screw driver] is turned off when initially feeding the case neck onto the K&M carbide cutting PILOT. http://www.kmshooting.com/catalog/neck-turner-tools/carbide-cutting-pilot.html [click on picture for expanded view]

Once it's fed on, then turn the power tool on.

That procedure will prevent scoring or scratching the inside of the case neck. The cutting tips on the end of the Pilot are very sharp.

Plenty of lube such as Imperial Sizing Die Wax applied to the carbide cutting Pilot and inside of the case neck [with a lubed Q-tip] will make things progress smoothly.

 

[artbosco]

I have K&M as well as Sinclair neck turning setup.

What I will tell you is that after using the expander on all my Lapua brass I had to turn down the cutter mandrel. It is easy and worked great. The cutter mandrels where so tight, I could not keep cases in the shell holder. A brief polish on fine sanding cloth, and everything works as it should. I resize after neck turning so the actual expander size is of no concern to me.

Minor point used for clarification only. The K&M Expandiron or Expander uses a Mandrel. The K&M Turner uses a Pilot [smooth regular or carbide with cutting tips] with separate Cutter blade attachment for actually shaving or turning of the brass.

I've used Lapua brass exclusively ... forever. I always use K&M Mandrels in my K&M Expander. And, I've never had to turn down my K&M Pilots.

Here's what I've noticed.

Sometimes specific pieces of Lapua brass are harder than others. I relate that to their annealing process and believe it imparts a hard crust to the outer surface which in some pieces impedes the expanding of the neck. To solve that issue, I've taken to rotating them and running them through the Expander Mandrel several times.

Because of the "crusting" I mentioned above, I've also noted that once I get past an initial thinner top layer cut of the brass [I use two Turners] the subsequent pass leading to my goal dimension, precedes much faster and smoother.

Also, at one time I used the Sinclair Power Case Holder and found that because it had a CONVEX [or rounded] head on the portion that contacted and tighten onto the bottom of the case, that the case would often spin even with extreme tightening of the tool. [I called them and suggested a flatter design]

Once I switched over to the K&M Shell Holder Power Adapter which has a FLAT head, the spinning went away, because the force being applied to the bottom of case was now being spread out over a much greater surface.

 

[spclark]

I've used Lapua brass exclusively ... forever. I always use K&M Mandrels in my K&M Expander. And, I've never had to turn down my K&M Pilots.

I've just finished processing 2 boxes of Lapua Palma brass. None woulda ever gone onto the K&M pilot without a pass first over the K&M Expandiron mandrel. A Sinclair E-30 mandrel's too small....

Once I switched over to the K&M Shell Holder Power Adapter which has a FLAT head, the spinning went away, because the force being applied to the bottom of case was now being spread out over a much greater surface.

So far all my neck turning endeavors have been achieved by chucking cases in the 1/2" chuck of my Milwaukee drill. I've yet to see any dimensional changes to the case bodies from this (I'm careful not to tighten the jaws much past snug) or marring of the surfaces.

If this gives some of you goose bumps, I can only say it works for me & doesn't appear to have an adverse effect on the cases. I turn about 85 - 90% off the neck surfaces before the first firing, then go to my desired neck wall dimension on the next pass after cleaning & resizing. Using a K&M tool makes this easy enough; with a Sinclair it's frustrating at best.