Tested my CVA 12ga double today with MAG-SPARK adapters, using shotgun primers. I was looking for some way to deal with my supply of #11 caps running extremely low. There don't seem to be any to be found, either. Dumb on my part for not stocking up, but it is what it is. I was looking at a muzzleloading forum on another site for something completely unrelated and saw a reference to the primer adapters. I figured why not give it a try and see what happens. I'm well stocked with shotgun primers, including some I'll never be able to use.
Adapters fit the gun perfectly, which was a good start. I popped a couple caps in each barrel at some dry leaves on the ground to see the reaction. Seemed to be way more blast than a #11 cap, which I had kinda expected.
Long story short, the MAG-SPARKS worked perfectly. Gun patterned well, seemed to produce a more complete burn (not as much fouling, more shots without needing to clean, etc.). I'm going to be doing more shooting, as I have a few more load combos to try, but the alternative ignition source is working better than I had hoped.
Are there some downsides? Yes, of course. To load a primer, unscrew the cap/firing pin, load a primer, screw the cap back on. After firing, unscrew the cap and remove the spent primer. IMO, this would be a serious PITA if you were shooting a round of skeet or trap. But for my use, casual clay shooting and hunting small game, upland birds, and waterfowl, it's not really an issue.
Upsides? Watertight, secure, reliable ignition every time. Plus, I can use an abundance of primers I already have, including a large quantity of old obsolete shotgun primers (Rem No. 57 and No. 69).
Bottom line? I ordered 2 more for my double rifle, another for my T/C Renegade, and a set for my ROA.
If you are experiencing a shortage of #11 or musket caps, this might be an option worth considering.
I don't have any stake in the company or their products, just passing on my results.