The barrel life of a 16” Naval gun is not 300 rounds. The life of the “lifespan” of the liner is 1,500 rounds. As for the number of rounds that can go through the barrel, that number likely is at least 100,000.
As noted above, this is not my line of work.
But the New Jersey and Puff were a fun topic in RVN.
Please note the last line.
“Approximate Barrel Life 3a 395 rounds”
NOTE 3a READS:
^HC rounds at 2,525 fps (770 mps) were 0.74 ESR and at 2,000 fps (610 mps) were 0.09 ESR. The Target rounds at 1,800 fps (549 mps) were 0.08 ESR, but it is noted that this gun could fire 2,860 Target rounds before exceeding liner life.
http://www.navweaps.com/Weapons/WNUS_16-45_mk6.php
Projectile Types and Weights 1a AP Mark 8 Mods 0 to 8 - 2,700 lbs. (1,225 kg)
HC Mark 13 Mods 0 to 6 - 1,900 lbs. (862 kg)
HC Mark 14 Mod 0 - 1,900 lbs. (862 kg)
Bursting Charge AP Mark 8 - 40.9 lbs. (18.55 kg)
HC Mark 13 - 153.6 lbs. (69.67 kg)
HC Mark 14 - 153.6 lbs. (69.67 kg)
Projectile Length AP Mark 8 - 72.0 in (182.9 cm)
HC Mark 13 - 64.0 in (162.6 cm)
HC Mark 14 - 64.0 in (162.6 cm)
Propellant Charge 2a Full Charge - 535 lbs. (242.7 kg) SPD
Reduced Charge - 295 lbs. (133.8 kg) SPD or SPDN
Reduced Charge Flashless - 315 lbs. (142.9 kg) SPCG
Muzzle Velocity Full Charge - New Gun
AP - 2,300 fps (701 mps)
HC - 2,635 fps (803 mps)
Full Charge - Average Gun
AP - N/A
HC - 2,525 fps (770 mps)
Reduced Charge - New Gun
AP - 1,800 fps (549 mps)
HC - 2,075 fps (632 mps)
Working Pressure 18.0 tons/in2 (2,835 kg/cm2)
Approximate Barrel Life 3a 395 rounds