So you said you had a cap fall off in Colorado and it cost you a crack at a bull. Were you using a different gun, with maybe a 209 ignition (I'm not sure what is legal in CO, still building points there, so I haven't muzzleloader hunted there yet).
It was a 209 ignition.
Last year I spent a lot of time working on cap and nipple fit. Not all #11 cap brands are sized the same. Also nipples, especially between brands, vary quite a bit. To weather proof and have reliable ignition, look for a snug fit and a way to reliably seat the cap. I actually have a shaped a small block of delrin (plastic) I put behind the cap and press it into place. Some guys use cappers that are rigid enough to firmly seat the cap. You need the cap to go on true (not cockeyed) as well to prevent misfires.
I also have a small drill the size of the flame channel and I chase the hole out every time I clean it. I often use a welding torch tip cleaner as well.
To summarize:
1. Determined a magnum cap you wanted to use (go with CCI or RWS)
2. Find a nipple that is a snug fit and try several caps on it.
3. Determine a method to seat the cap straight and firmly. If you "stretch" the side of the cap ever so slightly that will help weather proof.
4. Be vigilant about keeping the flame channel clean. One post I read once said "the root of all evil in muzzleloader is a dirty breach".
Follow this and you should have a gun that goes boom reliably.