5-Inch/54-caliber (Mk 45) lightweight gun naval artillery vs Rheinmetall L55 120mm tank gun?

What are you talking about?

The standard British Naval dual-purpose gun for destroyers and frigates since 1943 has been the Vickers QF Mk I, III or IV in Mk IV, Mk V, Mk 6 and most recently Mk 8 remote power mountings. This gun is actually a 4.45-inch (113.03mm) caliber rifled gun with a 45.0-cal barrel and an effective range of 12,500 meters firing full-bore HE ammunitoin. It was not ever made by the German firm Rheinmetall. The American naval gun, like the British has its origins in the end of World War 2.

The Rheinmetall DeTec 120mm L55 smoothbore tank gun is a very different animal. For one, it is not rifled - it is a smoothbore. For another, it is designed only for direct (low-angle) fire against armored vehicles. It is not like the naval guns which are rifled and intended for direct or indirect fire against a wide variety of target types. The Rheinmetall tank gun develops extremely high velicity by using non-exploding, sub-caliber APFSDS ammunition with an effective range of only 2,000 to 3,000 meters and pays the price in barrel wear. As a general-purpose naval gun it would be beyond useless. The analogy you are looking for there is with artillery, not tank or anti-tank guns. The Russian 130mm M-46 field gun would be the closest example since that is essentially a naval gun on a wheeled carriage.

Apples and oranges.

5 Inch Naval Gun

The Mark 45 is rifled giving it better accuracy and has a higher elevating ability so it can fire further like regular artillery, while the tanks gun is just a field gun with some elevating abilities.

Also the Mark 45 has a magazine to it which allows multiple rounds to be loaded at a single time and thus if the gun is properly maintained, can have a better firing rate than the tank. Which certainly adds to its firepower.

I can't tell you which one is best, but if they somehow fought and the Naval gun is well protected. I would give it to the Naval gun because they can put more rounds on target faster than the tank.

It depends on the projectile weight (or mass to be precise).

Kinetic energy is 1/2 M V^2 (Half mass times velocity squared), in kilogrammes and metres.

Doubling the velocity (eg. Leopard 2 compared to the others) gives four times the kinetic energy for a given projectile, and better accuracy as it has less time to fall in flight.

Even with a projectile half the mass, it would still be twice as 'powerful' in impact terms.

(If you include explosive projectiles, then it's a very different matter).

It depends on the type of ammunition used and range of application. Naval applications of today are more concerned with lighter cruise weight over long range gunnery.

OMGOSH I LOVE GUN's but............i just gave up on reading what ever you wrote ..am tired. I will say Tank gun for sure!

Too many numbers, hurt my head...