Does a small semi-auto CCW gun mean more fragile?
It sure use to mean that, but pocket guns have come a long way. Defensive ammo has gone a long way in recent years and the 38 special ammo your grandfather used in Law Enforcement is not the 38 Special you have today. I did some chrono tests with a Smith & Wesson Model 19 and the feet per second velocity between that and j-frame Model 637 was dramatic. I was breaking 1000ft per second with the j-frame and it really literally blew me away. I always thought that having a 4 inch barrel on a gun meant that it was shooting a load faster, but not the case with these two guns.
A friend of mine told me that everything he thought he knew about ballistics was thrown out the door when he got his first Chronograph and I agree. I also though that because a gun fit in my pocket that it had to be weaker. I am still trying to unlearn what I had learned with pocket guns, but another buddy of mine did some ballistic tests where he proved that his 32acp penetrated ballistic gelatin as well as a 38 special. While there is definitely some variations in results from firearms, the ammo you put in your Kahr PM9 and the 6rd or 7rd Kahr magazines that you are using, may be far more potent than you realize. The Kahr firearms are probable one of the most durable small guns out there and they have had several improvements over the years that put them above their competitors.