A measurement of weight. Usually applies to the bullet weight and/or powder charge. There are 437.5 gr to an ounce
Grain generally refers to weight- of bullets and gunpowder. The Mossberg 45B was a caliber .22 Long Rifle firearm. .22 LR is tpically a 40 grain bullet weight cartridge.
The XD40 will chamber any available commercial cartridge. If you're using it as a self defence firearm, try to find something as close to the weight of the cartridge you'll actually be using for that purpose. Rounds available go all the way from 120 grain up to 200 grain.
A shotgun is a firearm. A revolver is a firearm. A pistol is a firearm. A rifle is a firearm. If you want even more specific -- A Remington 1187 is a firearm (shotgun). A Smith and Wesson 686 is a firearm (revolver). A Sig Sauer P226 is a firearm (pistol). A Colt 6920 is a firearm (rifle).
No, Sword is not a firearm.
office discipline
Design of the firearm
Warrior + firearm
yes
Both "as regards" and "in regards to" are considered correct phrases. However, "in regards to" is more commonly used in informal communication, and "as regards" is more commonly used in formal writing.
No, he cannot have a firearm.
Condition of firearm and how desperate you are.
That depends if you are talking about the firearm or about the cartridge.