How much is too much, Help me Shadow and the gang!

[okierider]

Lyman says case mouth should be .423 and I am measuring .4150 on my reload Is that safe ? Factory Sig ammo measures .4205

[sqlbullet]

I would say no issue personally, but would probably back off the crimp some.  While nominally 10mm headspaces on the case mouth, in any controlled feed action it really headspaces off the extractor groove.

HOwever, you should be aware that if those are lead bullets, they are probably too small now and leading may result.

[okierider]

I put no crimp and they are coated lead bullets. I bought a undersized sizing die because I was having FTF issues with my lone wolf barrel and reloads.
These loads are the first time I had a pass on the Wilson gauge and I was all happy until I pulled  the calipers out . Thank you for the input .

[The_Shadow]

After all the pull-downs the average edge of the case mouth measures were 0.4220" most of all of the UW ammo was 0.4215" using a tapered crimp. 
While I have see stuff measure 0.4180" that had the bullets squeezed inward leaving a squeezed indention, too much crimp!  Also have seen ammo that were sent out with no crimp 0.4235".

Things to remember is seating bullets to their proper depth without any crimp being applied helps maintain good bullet diameter to case neck fitting, helps to eliminate case buckling and bullet shaving or snagging.

After bullets are fully seated to depth you can then apply a taper crimp without any bullet movement where the casing is gently being closed against the bullet which the slight taper can help reliable feeding.  Over crimping can buckle the casing, damage the bullet by squeezing it smaller at the crimp line but cause it to expand above and or below that area.  Understand that the LEE Factory Crimp Die can over squeeze the case mouth reduce bullet size (not good for the cast bullets or plated being squeezed smaller, the lack bore fitting seal) but can also leave the bullet loose inside the casing.  You can test that by twisting on the bullet to see if it will spin inside the casing or if there is any movement.  If loose it can also lead to poor propellant ignition, with alloy bullets that loose bullet in the bore will deposit lead in the barrels with excessive blow by.

10mm Cartridge Overall Length is usually 1.2500" - 1.2600" with Truncated Cone style bullets.  Bullets with MEPLATS 0.3000" with round edges will feed at these COL's, where as bullet with square edges like those Wide Flat Nose can cause magazine jams and failure to feed as these edges rub the insides of the mag tube or strike the edge of the feed ramp as they try to chamber.  The tipping angles can be such that the wide nose jams at the top of the tighter chambers before the case head can slide up the breech face.  Those Wide Flat Nose bullet may need shorter COL's down to 1.2420" especially those that have MEPLATS of 0.3200".

Hope this helps you understand the situations, but it can vary with different guns, barrels and magazines...

[okierider]

All info helps. Thanks Shadow.

[Univibe]

What I do with all handgun cartridges is use a four die set.   The third die only seats, and the fourth die only crimps.  By separating the operations I avoid the problems listed above.