In almost all cases a properly brass breeched Longshot will be superior to a singled Longshot. Having a clip accepting brass breech allows a greater capacity and thus rate of fire compared to a singled Longshot, while still allowing for the use of Stefans (provided your clips are modified appropriately and the brass you use is appropriate).
Singled Longshots are only useful if you've broken your Longshot's boltsled or you want to use darts which for some reason do not work in a brass breech.
Magazine, breech.
Yes. A simple google search would answer your question.
brass
Brass because it looks better, but be warned they will patinate. Even then it will have a nice vintage look.
Because woodwind is a bit girly.
Stainless steel would be better since it is hypo allergenic. Brass tends to turn skin that comes into contact with it green.
Yes. On a scale of 0 to 100, where annealed copper is 100, aluminum rates a 59, and brass averages 28. I say averages because there are actually quite a few different alloys of brass, but all of them are poorer conductors than aluminum.
Well, in my opinion, it is much better.
Copper fireplace sets are better in sense that it has a higher melting point than brass. On the other hand copper has a more dull color than brass and is harder to polish. Since the sets will be outside away from the fire, brass sets are more beautiful and easier to clean.
Brass is conductive. It's an alloy of copper and zinc, both of which conduct electricity ( pure copper is better, though).
obviously steel
chrome