Just carry one gun, for crying out loud. Your .45 ACP H&K is not going to be "ineffective." There's are very few ineffective guns - just lots of ineffective shooters. Fast, multiple hits delivered to center mass in any caliber will be effective. My "car gun" is a .44 Special Charter Arms Bulldog, but at 23 ounces empty and with a ridiculously long 3 inch barrel, it's way too big and heavy to consider carrying concealed, so it sits between the front seats in my center armrest.