Arinvolvo, read up on metallurgy and bullet types.
At a rainy-day class in the army in 1950, a Tech Sgt. was extolling the virtues of the M-2 Carbine, "... yada, yada, 2600 feet per second, 750 rounds per minute, so fast that there are two rounds in the barrel at the same time..." After some quick head math, my stupid 17 year old hand went up, "Uh, Sergeant, I think the bullets are about 200 feet apart, roughly." Big mistake on my part. For the next six months, every time he saw me, it was, "give me 50!!!"
How about the old saw, "the M-16 is made so that the bullets keyhole so that they do more damage"
At a gunshow, trying to buy a lightweight bullet for my Ruger BH in 30 carbine, I asked a dealer if he had any 90 grain bullets in .308. He patiently explained to me how the 308 wasn't intended to shoot such a bullet.
One of the best, was a guy showing off his old Colt SAA and telling me how it belonged to his Great Grandpa who was a Texas Ranger for 48 years, and dedicated his life to using "this very gun" to kill a bad guy every day that he was in the Rangers. I didn't even do the math. God, what a stack of body bags.