Case prep/Mouth bell question

[perimedik]

Greetings Folks,
How do you put a "bell" on the mouth on a case for cast reloading. I keep reading about it here and there so not to eff up the brass. I understand the concept, however,

is it a tool?
Is it a die?
Is it a specific measurement?
Is it a finesse by eye artform or technical skill?

Can anyone help out, pic or two would be good for reference.

Thanks

[stubshaft]

It is called a Lyman "M" die. It has an internal spud that expands the case slightly and flares the mouth to accept cast boollits.

[btroj]

I use a Lyman M die for rifle cartridges. For pistol, and straight case rifle, most die setts come with an expander for belling the case mouth.
The whole key is getting enough belling to not shave lead while not having so much that it prematurely causes case failures. This is a feel type thing.

[462]

Perimedik,
Here you go: http://www.lasc.us/Brennan_LymanMDies.htm

The M-Die's advantage, over a conventional die, is that it adds "expands" and adds a "step" that properly aligns the boolit to the case. A conventional die only "flares" or "bells" the case mouth, so that a boolit will not sit squarely in the case and will be seated at some non-optimal angle.

[rocice]

Great product http://www.lymanproducts.com/lyman/dies/rifle-die-details.php?brand=3&cartridge=26&die=52

[deadwooddick]

A conventional die only "flares" or "bells" the case mouth, so that a boolit will not sit squarely in the case and will be seated at some non-optimal angle.

So my RCBS expander plug (to enable thumb seating) allows the bullet to tip ? Odd, since runout on loaded 40-90 BN rounds measures 0.001 to 0.003" with that RCBS expander.

My 2¢, if you get tipped bullets (excessive run-out) something else is going on.

[MikeS]

I think a lot of other die makers have been making their expanders similar to the Lyman M ones. The only difference is that you can buy the Lyman M expander dies as a 'generic' die, being caliber specific, not cartridge specific. This is mostly for folks loading cast boolits in rifle bottleneck cartridges which don't normally come with an expander die. I use the expander die from my RCBS dies, and they work fine for cast boolits.

[mooman76]

You pistol dies come with a die that will bell the case mouth. It simply will flare the case mouth like a funnel so you can start a lead bullet into the case mouth without cutting into the lead or damaging the case mouth. It is explained in your die set instructions. Rifle die sets usually don't have this die so you can get the Lyman M die to do it or you can get a universal die that will do basically all calibers.

[MtGun44]

Pistol dies will bell the mouth if you set the expander deep enough. You can also use
the Lee Universal Expander Die to bell the mouth of any cartridge. Works great.

Bill

[Hip's Ax]

I use the Lee Universal Expander Die to bell the mouth just enough to seat without shaving lead then I make the bell go away with a crimp die.