“Seat and taper-crimp in one stage?” or “How much taper-crimp is enough?”

[Lucas McDennis]

The two questions are equivalent for me, in that my Loadmaster presses allow me to use the RCBS powder-check only if I can seat and crimp in one stage. If I want to break seat/crimp into two stages, there’s no room for the powder-check.

This is not a problem with revolver bullets having a crimp groove that gets roll crimped. Simply adjust the seat/crimp die so that the crimp ring engages the case mouth roughly coincident with the back of crimp groove. Then as the crimp turns in, there is no interference between brass and bullet to iron-out or shave the bullet. The crimp turns into the groove, and if everything is set up right, one achieves the desired amount of crimp, and the front of the crimp grove is aligned with the top of the brass (uniform case length required, etc. or allow some extra margin in set-up).

Now I’m wondering if the reason I can’t seat/crimp those calibers head-spacing on the case mouth in one stage is because I have been using too much taper crimp. With a moderately heavy taper crimp (1/2 to ¾ of a turn of Lee seat/crimp dies), the bullet’s bearing surface gets ironed out as it slides past the gradually tightening crimp. In the case of properly over-sized cast lead bullets, a sliver-ring even gets shaved off, damaging the bullet and making a mess of things.

But am I applying to much taper crimp? In other threads here, knowledgeable people say that the purpose of the taper crimp is only to remove the bell; not to hold the bullet from jumping crimp. Rather, holding can only be done by case mouth tension, established by the sizing die. At least one writer points out that too much taper crimp is counter-productive to holding the bullet in place, because the bullet undergoes more plastic deformation (less “spring back”), while the brass is more elastic, (more spring back). The result being less bullet grip from over-crimping; not more.

So, all of this is to answer the question: Can I reduce the amount of taper-crimp I’m using, and combine seating/crimping in one operation, so I can use the powder check on calibers such as 9 mm and .45 acp on my Loadmasters?

Thanks in advance.

 

[rcmodel]

Yes.

If you are shaving lead or bullet jacket during seating & taper crimp, you have too much crimp.

rc

 

[243winxb]

When brass is all of a different length, some will shave lead, some will not. Plus, not all seating dies are correct. Some will start taking out the bell sooner than other. This requires the seating die to be modified to seat & crimp with the same die. Adjust the bell on the shorter case of the lot. Set the taper crimp on the longest case of the lot.

 

[rcmodel]

Chamfering the case mouths also helps a bunch.

rc

 

[Walkalong]

There is so little bullet seating going on when the proper taper crimp is being applied to the 9MM or .45 ACP, that there will be no lead shaving.

Seat and "crimp" in the same step to your hearts delight. No worries.

 

[Lucas McDennis]

Thanks all.

As per Walkalong's observation that "There is a little bullet seating going on when the proper taper crimp is being applied..." I would agree, and that's what causes the deformation and/or shaving, when setting the crimp to Lee's suggestion (1/2 to 3/4 turn past the point where crimp ring contacts the case mouth). I think the key is to use less than that much crimp; just enough to remove the bell, and no more.

 

[LiveLife]

Been seating and taper crimping in one step for happy 16 years even with lead bullets.

 

[243winxb]

just enough to remove the bell, and no more.

No, just enough taper crimp to let the round chamber.

 

[Lucas McDennis]

Ah! Yes, of course. Just enough to chamber.

 

[Walkalong]

I'll respectfully disagree with 243winxb. Just enough to remove the bell or a hair more. If that isn't good enough to chamber, you have other problems.

Thinner brass will measure differently.

 

[243winxb]

Thinner brass will measure differently

And thicker brass will require more taper crimp. Post #4

Notice how just a light taper crimp on the 1.239 O.A.L. round dropped the round another .004 deeper.

Amount of crimp .001" Round headspacing on the bullet. Photo Thread http://www.thehighroad.org/showthread.php?t=506678

 

[Lucas McDennis]

Thanks very much to all of you. I now understand I was over-crimping my auto caliber loads, and can go back to seating/crimping (de-flaring actually, in these cases) in one operation, and thus free up a position on my Loadmasters for the powder check.

 

[beatledog7]

I have yet to load a 9mm round that I had to taper to achieve easy chambering--bullet seating straightens out the flare. Maybe when I try some lead bullets I'll need to taper.

 

[Striker Fired]

I seat and crimp seperately but my LNL has enough stations to do so.You should be able to get away with them combined.I did it for a while with my RCBS dies till I got all Dillon crimp dies,when I switched I did notice more consistant OAL .Lead bullets may vary in OAL a little more than plated or jacketed ,possibly,but not enough to worry about in pistols,

 

[Walkalong]

And thicker brass will require more taper crimp. Post #4 .........Notice how just a light taper crimp on the 1.239 O.A.L. round dropped the round another .004 deeper.

The flare wasn't removed until then, holding the round back, and/or his chamber wasn't parallel all the way to the shoulder, being a hair tighter towards the end. A dulling reamer with a curve at the shoulder instead of a nice sharp 90 degrees.

So yea, a bit more taper crimp could help here, but it was only needed because of another problem. Post # 10.