Crabo: If the 'Topple Rule' is the same as when I shot Metallic Silhouette 30 something eyars ago it means the target has to topple, or fall. It cannot be just 'rung' - that is, hit by the bullet that makes it ring when hit, or 'rocked' - which means 'wobbled' or almost toppled.
It used to mean that you hafta knock it off its perch and make it fall over.
Our favorite 44 magnum load for the Metallic Silhouette was the 240-245 gn keith style swc, gas checked or otherwise, over the factory load of Winchester 296: 25 gns for cast slugs and 24 for jacketed. I once got the loadings mixed and shot 25 gns under 240 gn jacketed slugs but in my Ruger Super Blackhawk it didn't matter - they still hit those rams like it was meant to be. Some guys mixed their loads to shoot milder ones at the 50 and 100 yd targets, some didn't.
Most of our shoots were during the dead of winter and it would get really cold on that firing line - one of our shoots saw temperatures to minus 32 Farenheight and it was nasty that day.
We found that when it was so cold like that even with the 44 magnums we had to hit the 200 yd ram high center to knock it over. If we hit it low it would ring out and rock or wobble but often no topple. Same thing with the 200 gn 357 loads - either you clocked the ram high center to topple it or all you got was a 'ringing' awareness that your slug had hit the silhouette. Mikey.