Just finished the test on the copper foil. Short version of the analysis is that it's difficult to work with compared to the aluminum.
First off, let me say that the manufacturer says to punch a cap and then slide the material in the tool to punch the next. So none of the material I've punched can be easily and smoothly slid through the tool. Not the single pop can, not the double pop can, not the aluminum in the post above but especially not the copper foil!! It's too soft and the edges seem to follow the punch down into the tool. It's ery sticky and needs to be worked to free it up. The aluminum can be a bit sticky too but it's tolerable and I can work with it twice as fast as the copper.
That said, the caps are very nice but no better than the aluminum. I expect that they will both function well on the gun but I'm going to charge these two batches and compare at the range.
Notice how much more ragged the copper is along the edge compared to the aluminum.
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