ORIGINAL: cayugad
eldequello - have you ever noticed that mag spark to cause any damage to the hammer springs? I talked to a fellow at a gun shop that used one, and he said he would fire the sidelock and it would cock the hammer from the back pressue. The gunsmith "suspected" a weak hammer spring. He said this never happened until he went with the mag spark.
Well, it hasn't happened to me. I franky don't see how it could happen with a Mag Spark,as the hole in the bottom of the Mag Spark nipple is every bit as tiny asin a No. 11 size nipple. In addition, the back pressure would only push the primer up against the firing pin inside the screw-on cap. In my Mag Sparks, there is no evidence of the primer moving at all...... And I have used some pretty hairy powder charges with them!
However, years back there were similar devices that permitted the use of small rifle primers. I've used a couple of these, and one had a constant-diameter hole straight through under theprimer cut. I DID get hammer blow-back with this kind, with every rifle I tried it on. So I suspect the nipple design was faulty, not a weak mainspring.