Crimp diameter minimum

[longnkrnch]

What is the smallest diameter I could taper crimp to without causing issues? I am hitting right at .475 right now and still having elongation when chambering unless I ease the rounds in.

[Hoot]

What is the smallest diameter I could taper crimp to without causing issues? I am hitting right at .475 right now and still having elongation when chambering unless I ease the rounds in.

IMHO if you're crimping into a cannelure, then .474 doesn't seem to stress the case mouths too much. Into a smooth, hard copper body, that degree of taper crimp will in all likelihood cause the mouth walls to thin permanently after a time or two. The net effect of the thinning is that the same amount of taper crimp the next time will not have the same effect. The issue has been at the forefront since I started using this caliber. The heavier the bullet, the more it pulls out during chmbering due to momentum. Switching to a side/stab/LeGendre crimp will also scar the brass, but not at the mouth and if you crimp in the same spot every time, even the scar does't matter. Trying to quantify that kind of crimp in terms of diameter gets a bit more tricky as the width that the bite is ground down to becomes a factor. Narrower being more effective in terms of bite, but less effective in surface area affected. There is a balance to be had though and a .474 stab crimp will probably deliver 3x the retention into a cannelure or driving band groove compared to the same degree of taper crimp. Probably 2x into a smooth, hard sided bulet without distorting it enough to impact accuracy. Again, my experience has been that stab crimping has a measurable but not significant impact upon accuracy depending upon whether you're into a cannelure/groove or denting the smooth side of a bullet and worse the further back it is placed on that bullet.

Unfortunately, the best I can recommend is to switch from the taper crimp to a stab crimp. There are several "stickied" threads at the top of this sub-forum with easy to follow instructions and me to answer any holes in them. If your pockets are deeper than your handiness with and access to tools, drop me a PM and we'll work something out.

Hoot

[wildcatter]

What is the smallest diameter I could taper crimp to without causing issues? I am hitting right at .475 right now and still having elongation when chambering unless I ease the rounds in.

IMHO if you're crimping into a cannelure, then .474 doesn't seem to stress the case mouths too much. Into a smooth, hard copper body, that degree of taper crimp will in all likelihood cause the mouth walls to thin permanently after a time or two. The net effect of the thinning is that the same amount of taper crimp the next time will not have the same effect. The issue has been at the forefront since I started using this caliber. The heavier the bullet, the more it pulls out during chmbering due to momentum. Switching to a side/stab/LeGendre crimp will also scar the brass, but not at the mouth and if you crimp in the same spot every time, even the scar does't matter. Trying to quantify that kind of crimp in terms of diameter gets a bit more tricky as the width that the bite is ground down to becomes a factor. Narrower being more effective in terms of bite, but less effective in surface area affected. There is a balance to be had though and a .474 stab crimp will probably deliver 3x the retention into a cannelure or driving band groove compared to the same degree of taper crimp. Probably 2x into a smooth, hard sided bulet without distorting it enough to impact accuracy. Again, my experience has been that stab crimping has a measurable but not significant impact upon accuracy depending upon whether you're into a cannelure/groove or denting the smooth side of a bullet and worse the further back it is placed on that bullet.

Unfortunately, the best I can recommend is to switch from the taper crimp to a stab crimp. There are several "stickied" threads at the top of this sub-forum with easy to follow instructions and me to answer any holes in them. If your pockets are deeper than your handiness with and access to tools, drop me a PM and we'll work something out.

Hoot

And if this doen't work, use both crimps at the same time..

..t

[Texas Sheepdawg]

On my FMJs, I initially taper crimp to about .476-.478"
then I apply my side crimp to .472, down .066" from the case mouth
Then taper crimp to .474".

That's why I now have two Rock Chucker Presses.