Hubby asks “Why add another caliber when you already have ammunition magasines for .223/5.56mm? Besides, .223 is a great self-defense caliber and the M4 is a sweet, tight, fast little package.” (his words, not mine...) p.s. .30 caliber means bigger weapon that needs more room and weighs more - carries less bullets.
Well, same reason why folks go with .45 rather than a 9mm for a pistol. Less ammo, more weight, but better stopping power, longer range, etc. Truth be told, I probably will just stick with 5.56 since I do have the mags, and it’s what I’m trained on and used to. The 7.62 thing is something I keep threatening to do, but I probably won’t.