They work fine in .45 ACP revolvers that have headspace shoulders. In those instances the Rimz clips are simply providing a surface for the extractor to bear on. If you have an early Colt 1917 without headspace shoulders, or a Webley Mk VI, Colt NS, or S&W HE2 that has been converted from .455 to .45 ACP then the Rimz clips provide too much cushion and cause occasional misfires. My early Colt 1917 without headspace shoulders misfires about 15% of the time with Rimz but I've had no misfires with the Colt using steel clips. Conversely, I've experienced no misfires using Rimz clips with a S&W 1917 or Brazilian, due to the headspace shoulders providing a solid resistance to the case being driven forward by the firing pin.
-Bob