[jtduncan]

WalterGA is on the money.

I had some Berry's 180s and 165 grain 10mm FPs tumbling.

After a while we noticed my crimping was way too tight.

Use a very light crimp on the plated bullets. Otherwise, you compress the bearing space of the rear of the bullet, elongate it, and it doesn't have a tight fit going down the barrel so it comes out like a poorly thrown football tumbling and wiggling wildly.

Try bumping up the charge a tad and lightening the crimp.