crimp


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area51
June 10, 2012, 04:36 PM
Which is the best crimp out of these 3 ? 158 lswc over 3.6 hp38. I want to up the charges to 3.8 and 4.0 - shooting these out of s&w 2" pre 36, m19-4 and a blackhawk 6"

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rcmodel
June 10, 2012, 04:38 PM
I can see no crimp on the one on the left.
The one on the right is way too much for a mild load like that.

So, the one in the middle.

rc

56hawk
June 10, 2012, 04:44 PM
Yeah, second one for 38s third for 357s.

area51
June 10, 2012, 04:44 PM
I can see no crimp on the one on the left.
The one on the right is way too much for a mild load like that.

So, the one in the middle.

rc

Thanks RC ! You are a real asset to this forum. A reloading guru !

Friendly, Don't Fire!
June 10, 2012, 05:02 PM
Yup, the middle one, fer-sher.

BYJO4
June 10, 2012, 05:06 PM
I would increase the crimp slightly on the #2 round. The 3rd round is too much.

area51
June 10, 2012, 05:22 PM
Many thanks Gents. Back to the reloading bench listening to a medley of Getz and Chet Baker for a couple of hours....

rcmodel
June 10, 2012, 05:27 PM
Rough rule of thumb:

The hotter the load, the more crimp you need to prevent recoil pulling the bullets.

Your 158/3.6 HP38 is not a hot load.
It's barely a starting load so it won't have much recoil.

rc

Friendly, Don't Fire!
June 10, 2012, 05:37 PM
I realize others are commenting that this is a mild load, let's for a second pretend that the load is a fairly wild load, or even IS a wild load.

In that case, it is best to shoot a cylinder full of them and after each shot, check to see if there is any bullet jump from the mouth of the remaining cartridge cases. Recoil, especially on wild loads with heavy bullets will tend to cause the bullet, or the pill, to begin jumping forward. You do NOT want this to happen - at any cost!

If you get to the third shot or so and if the remaining cartridges have pills that have jumped enough, it is possible for the last one or two to actually jump out of the case, of course, powder would be dumped into the cylinder holes around the same time that flame and sparks are coming from the round being fired.

That would be the worst case scenario which could end up in a kaboom.

The least that could happen is the cylinder jams due to a pill that has jumped forward so it is now beyond flush with the front of the cylinder.

Walkalong
June 10, 2012, 05:52 PM
Medium roll crimp on a 125 Gr lead bullet (The weight is not relevant)

http://www.thehighroad.org/attachment.php?attachmentid=104460&stc=1&d=1251676348

homatok
June 12, 2012, 12:11 PM
You need to be more concerned with bullet-to-case tension rather than crimp! Lead bullets are prone to being sized down during the seating process, a concern that is addressed by controling (i.e."M" die) bullet fit (into the case). Too tight of a crimp can result in bulging the cartridge to the point it will not chamber and it will also, at the very least, result in the bullet being damaged when it is fired, which leads to gas cutting and leading.
●Too much crimp only ruins tension, use ONLY enough to hold bullets under recoil.
●Toughen the bullet to open the crimp and prevent slump and skid.
●Changing the crimp alone does not solve the problems that can be caused when firing opens it. A very light crimp that does not open will still damage a bullet.

Experiment with your crimp. if you can run your finger nail down the finished cartridge and it does not catch on the brass that is enough. If the bullets are not walking forward under recoil that is enough. if they are not being shoved back into the case in a levergun that's enough.
Take a new case, chamfer inside and out, then apply a small bell. Slip the lead bullet in and crimp lightly (into a crimp groove) just so it straightens the case. At this point you should have just a bit of an edge on the case mouth. This is verified by using the cylinder to make sure they will chamber.

If your bullets are moved forward until the cylinder jams, simply push them back in with your thumb, fire them, and then reset the crimp die, screwing it downward another 1/16th to 1/8th of a turn. It only takes a little to tighten the crimp. When the bullet is gripped tighter than tapping with any tool will loosen, (short of banging on it hard), you know it's there for good. Sufficient crimp has been achieved when there is just enough crimp to leave a straight case (from the belling die) and have a bit of an edge that clears everything. Crimp must only be applied at the edge of the case mouth. If the crimp is excessive, it will bulge the brass below it, which is no good and will cause the cartridge to be too big to enter the chamber!

area51
June 12, 2012, 01:36 PM
You need to be more concerned with bullet-to-case tension rather than crimp! Lead bullets are prone to being sized down during the seating process, a concern that is addressed by controling (i.e."M" die) bullet fit (into the case).
Funny you mention the M dies. They were ordered about 3 das ago.

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