Taper crimp size

[tommac919]

Just setting up a string of 10mm with rem 180gr mc flat top and Blue Dot, Star line brass... For a glock 20.

wondering if any reccommendations on the amount of taper crimp? ( crimp/seating die set up as specs, will measure again as I don't remember what it was yesterday. it was fairly tight as it took a few raps to pull the heads ... running lenght 1.250)

BTW, neck to spec, tight on head, smooth case... no deform/marks showing showing on head. After pulling bullet measures .400-.3995

[BRL]

Surprised no one has made any kind of a recommendation to you yet.

Understand that I'm only capable of a reply because I don't consider myself to be any kind of an expert on this subject, so please take it for what it's worth...if anything.

Since the cartridge headspaces on the case mouth in my Glock barrel, what I do after fully seating the bullet, is to raise the cartridge to the top of the press stroke and then screw the taper crimp die into the press until I get that "feel" of resistance that I'm looking for, and if all seems right I will set the lock ring at that point.

Pretty much means the removal of the flair I put into case earlier in the reloading process, and not a whole lot more when the bullets I'm using do not have a cannelure.

That method has worked reliably for me.

[The_Shadow]

I must have missed this post.
If your 10mm cases are sized correctly diameter (0.4215" - 0.4230") they should hold the bullets fairly tight and length is uniform so to will be your crimping.

I seat my bullet to proper depth without any crimp being applied, because the bullet is still moving deeper as crimp is being applied if doing this in a single step.  What happens if done in a single step, is the case starts to close in on the bullet, the rough case mouth can impede the bullet's travel (in the case of plated or cast bullets it can snag and start to shave off bullet material.  I use two separate steps, seat fully w/NO crimp then crimping in separate step.  That has provided me the best ammo and 100% reliability for feeding.

I like to taper the crimp to fully remove the flaring of the expander setting.  0.4230" is in most instances to straighten the case back and against the bullet.  I try to set my taper crimp a little bit more rocking the knife section of the caliper on the very edge of the case mouth lip to measure 0.4215" - 0.4220".  This little extra taper seems to provide more consistent feeding in all of my pistols. 

If you apply too much crimp, can cause the casing to slightly expand below the crimp making for a loose bullet fit, as such you might be able to spin the bullet inside the case by twisting it.  The use of the Lee FCD die, can squeeze the bullet (if soft) as it sits in the casing reducing its size, making for a loose fit as well.

Short cases will not get as much crimp applied, if the die is set for longer cases.  Some bullets can measure smaller than 0.4000" so check this prior to running your batch. 

Hope this helps out and good luck!

[tommac919]

<"Hope this helps out and good luck!">

Yes it does, great explain.... Looks like I got it right.