In the reloading room...

[jmorris]

I get mostly .3565 diameter.

There is a difference between resolution and accuracy. If you are trying to measure to a half a thousandth, you are using the wrong tool.

You need a micrometer not a caliper.

 

[PO2Hammer]

In 38/357 I crimp plated bullets slightly, just enough to see a slight deformation in the surface of the bullet at the case mouth . I use either a taper or profile crimper. This has worked well for me. I use it with my lightest loads and the fairly stiff loads, 158 @ 1000 fps in magnum brass. Recovered bullets show a mark at the crimp line, but never any evidence of damage, even with the thinnest bullets (Rainier).

 

[gwpercle]

Awesome ... Sounds like you got this one by the tail on a down-hill drag ...
... Keep on Keeping on and Load Safe ...

I've got "pet loads" if you need some to get started .
Gary

 

[41 Mag]

If after everything else your still curious, load up a dozen or so rounds with your intended load. Put six in the cylinder, shoot the first and measure the rest. Shoot the second and repeat, do this until you down to the last round. Load 5 more ahead and repeat. If after a couple or more cylinders have been shot there is no movement from the initial 6th round you are good to go.

If it moves anywhere after any of the first string, adjust the crimp slightly more and repeat. Sounds overly simple, but it has worked for years with my magnum revolver loads. I found decades ago that trimmed cases and crimp can and do influence accuracy. With most of my revolver loads being used for hunting I try to eliminate everything I can from the overall equation. Most of the time that just leaves me.

 

[rdnktrkr]

I like the taper crimp for smooth sided bullets and use a roll crimp if it has a groove. I don't like your theory about seating lower and roll crimping oner the taper due to the possibility of increasing pressure, I was taught to stay around OAL for that reason.