I think he is talking about musket caps.

As mentioned, just pinch the cap a little so it will grip the nipple.

As far as how many shots you can get with a nipple...

Certainly several hundred shots to a thousand plusif you don't dry-fire and detail clean the nipple after every shooting session. I shoot the same nipple until it begins to flatten out from use making it difficult to cap or as the flash portopens up from useand I end up getting a bunch of blowback. But that happens over a long time if you care for them.