.243 Win and 6 ARC Mandrel Expanding

[hhudson]

Most of my rifle shooting is with a .243 Win (bolt) and a 6 ARC (gas). The more I shoot the more I am interested in precision and precision reloading so here I am asking about mandrel expanding. I thoroughly enjoy the reloading process so the added steps is not a downside for me. That said I’m not competing and don’t want to be deeply financially invested in mandrel sizing.

I have a few questions.
First LE Wilson mentions their die is for new brass. I was under the impression that it would be done every loading.

Second how much undersize of a mandrel should I buy without spending a couple hundred bucks on all of the available sizes that I’ll probably never use? Maybe .002 so .242”?

Lastly is there a die that can do .243 and 6 ARC with the same die, obviously some vertical adjustment and correct shell holders would be needed.

 

[chromatica]

I like expansion with the Lee Collet Die to be the last brass operation on the neck. The Lee Collet dies ship with mandrels that are .002 smaller than caliber so for .243 it would be .241 in diameter. The mandrel has a tip on it that mates with the flash hole and keeps the process centered. It also has steel petals that close down over the outside of the neck while the mandrel is in place. You can purchase custom undersize mandrels from Lee. I have done that and so now I am running a .240 mandrel in my 6ARC die.

 

[Allen Corneau]

I shoot a 6BR, but it should be relevant to your situation.

I use unturned Lapua brass.
I use a 0.264" neck bushing during full-length sizing (no expander ball).
I use a 0.240" mandrel after wet tumbling with pins.

My target "neck tension" is 0.003" so when I check the brass afterward with gauge pins (half-thousandth increments) I get about 85-90% at 0.240" and the remainder at 0.2405".

If I get one that feels weird/soft when seating the bullet I just set it aside and mark it for blow-off/sighters. Those with a fancy AMP press can do a similar thing by referring to the graph on screen and culling the outliers.

This system works great for me and gives me loaded rounds that falls within my tolerances for what I need.

 

[ShaunBrady]

Most of my rifle shooting is with a .243 Win (bolt) and a 6 ARC (gas). The more I shoot the more I am interested in precision and precision reloading so here I am asking about mandrel expanding. I thoroughly enjoy the reloading process so the added steps is not a downside for me. That said I’m not competing and don’t want to be deeply financially invested in mandrel sizing.

I have a few questions.
First LE Wilson mentions their die is for new brass. I was under the impression that it would be done every loading.

Second how much undersize of a mandrel should I buy without spending a couple hundred bucks on all of the available sizes that I’ll probably never use? Maybe .002 so .242”?

Lastly is there a die that can do .243 and 6 ARC with the same die, obviously some vertical adjustment and correct shell holders would be needed.

I do something similar to Allen, size down 4-5 thou under the bullet diameter, open it back up to 2 thou under with a mandrel.

With new brass, I follow the same process as reloaded brass, size down, mandrel up. If you want to minimize bushings, maybe start with 5 under. It'll start at 5 and be down to 4 after a few firings when the neck hardens. Opening it back up at least 2 reduces variations in the neck tension.

I use the Lyman M dies a lot. I also have mandrel holders primarily intended for neck turning from Sinclair and KM. The Lyman dies are sometimes listed by cartridge, but there generally only 2 part numbers per bore. Long and short action. I buy the M dies even though I have mandrels for the other tools to avoid having to reset the die when I switch cartridges. After setting them up for a given cartridge, I put that die in the box with the sizer and seater.

How many more steps it adds depends on your approach to lubricating the ID of the neck and whether there needs to be an extra cleaning step to remove that lube.