Lucas McDennis
Member
- Joined
- Dec 26, 2010
- Messages
- 22
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.
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.
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