PS..... i call BS on those caps going off "Every time". ( i got a bunch of # 11's i'll sell you cav....)going to the musket cap was the best thing i ever did. they are easier to handle and don't foul in wet weather as easily.... i live in Orgon...trust me on that one...its eay to do, just buy a muscat nipple and screw it in....your good to go...
The only time I have ever had #11 fail was because I purchased substandard caps, or the rifle was not prepared or maintained properly. As far as heat produced by the musket and the #11 cap, the temperatures are almost identical. Granted the musket cap will produce more of it, but if the rifle is set up right, while more is better it is not necessary. Also, I hate to change the set up of the rifle. Get a stainless steel hot shot #11 nipple and you're good to go IMO.
What brand of caps did you purchase? I would be interested to know. I've hunted with #11 caps more years then I care to count, in rain, sleet, snow and sunshine. I even dropped a rifle in a creek once. Put a new cap on it and it fired just fine.
Some of the dangers of changing the set up of a rifle to shoot something it is not intended to shoot are, a musket cap can over time weaken the hammer spring causing it to fail. it can blow back the hammer to a cocked or half cock position. Anytime you're forcing something to change course that fast, I can not believe it is good for the metal and parts. Also I had a heck of a time water proofing a musket cap. Granted you can pinch the cap and make it stick to the nipple better but in most #11 caps, they will almost water proof themselves. A little birthday candle wax along the base is a good addition but if you care for the rifle you hardly need it.
Before you shoot your rifle swab the bore with pure Isopropyl Alcohol 91%. Then some dry patches. Next I take a clean patch push it to the bottom of the breech and fire a #11 cap. Pull that patch and inspect it. If if shows good burn marks, blow one more cap for good measure and then load as normal. You now a clean bore, with a dry load on a clean fire channel. A good #11 cap will fire that off.
If you are one of them that likes to put the rifle up for the night and then find the cap fails in the morning, don't blame the cap. Blame yourself and the manner in which the rifle was treated.
You are more then welcome to call BS on all of this. And use your musket caps if you feel more comfortable. But in my experience, I never saw the need for them. The only rifle I use a musket cap on is my T/C Black Mountain Magnum which came with musket cap ignition. As I mentioned, I hate to change the factory set up of the rifles.