CCI #11 Mag caps seem to work OK for me, but there is no comparison when you introduce the 209 shotgun primer - it is in a different class entirely! In my sidelocks, the 209 will blast a flash of fire right out the muzzle, just like a Large Rifle primer in a centerfire rifle cartridge case!! In addition, I have NOT FOUND musket caps to be any better than #11 CCI Mags.

Larry