Undersize die for 40 S&W

[basman]

I have read the posts about using an undersize die. But is it really needed? If I am loading long I do not want the lenght to shorten during feeding, etc. The Crimp is solid and seemd to work well.

Thanks

Basman

[Sam]

I haven't read about the undersize die, so I really can't say what the rationale would be for buying one. But, if you are experiencing feeding problems in any caliber, it is more likely due to an improper adjustement of the standard dies than any need for something undersized.

Brian made a great post somewhere, that I'm way too lazy to search for, about crimping and how what is really needed is only to restore the factory taper and dimensions to the round. Mic a properly sized bullet. Add the thickness of the brass. .10 for each side of the case. What you want to end up with is a loaded round that is .421 at the case mouth. (.401+.10+.10) A "crimp" may roll the brass over and actually increase the diameter of the round. An undersized die would ostensibly mash the brass into the bullet and upset the accuracy. There could be other implications like elevated pressure too.

I'm with you Bas, if the crimp is solid and works well, there is nothing to be gained and much to be lost.

[kimel]

Take a look at this from the FAQ:

Reloading Bulged Brass

The Lee and EGW (which is just a modified Lee) Undersized dies have nada to do with crimp. They are resizing dies.

Are they needed? Only if you buy once fired brass, shoot a pistol with a chamber that is SAAMI spec or tighter, and don't like having feed failures.

If you buy all new brass, don't shoot a pistol with an unsupported chamber and never end up with any random range brass in your brass bag then no, you don't need the undersized die.

Hope that helps.

[eric nielsen]

Not necessary if you shoot a Glock...

Regarding shortening, I've also found that using nickel 40cal cases and avoiding getting any spray lube in the case mouth area cured that 100%.

The expander button is what sets your bullet pull. Does anyone know if Dillon has changed the size of theirs since I bought my press - 1992? Wish mine was smaller.

[kurtm]

Never need to "undersize" .40. Using a regular dillon die and using range pick up brass, every once in a great while I will get an over size case that won't gage. but I certainly NEVER sort brass by head stamp or primer mark. If they aren't pushing back into the case now, you don't need it! KURTM

[TBF]

Caspian28r,

Dunno if they changed, but you can always make them smaller.

I have always managed to cobble something together allowing me to chuck the expander in a drill, and used emory cloth to make them smaller.

I like -.003 - .004 smaller than bullet dia measured close to the belling area, with the majority of the expander smaller still. Most of the expander is just a guide for the belling area.

This gives extremely good bullet grip, better than any crimp could ever do.

Autoloader crimp as mentioned above , is just to remove the bell anyway, and does very little to prevent bullet setback.

Travis F.

[EricW]

If your Dillon die won't go down far enough to get all of the Glock bulges out, it's a simple matter to just grind down the die so that it does.

It's just as effective and you'll save yourself $20 plus ship.

[Sam]

Thanks, for getting me on track Kimel! I was clueless....again.

So far, I've manage to get by fine with the Dillon dies. I always drop check my match ammo in the barrel it's going to be fired through. And I do find an oversized round now and then.