it depends if they're strike anywhere or safety matches. making them with strike anywhere will probably just blow up while you're making it. safety matches can be compressed like crazy, I heard.

They can be compressed like crazy, but that sensitivises them for strikes. My father told me about this method - get some match heads into a nut, screw it tightly with two screws, tie a string and use that string to accelerate into some hard object. Luckily, no one got hit by exploding screws.

Supposedly a wild strike caused the steel hammer to strike the steel pipe and spark, and there was a narrow flammable channel next to the dowel leading to the main charge.