Jenrick

October 5, 2008, 09:14 PM

Found an interesting article on naval guns. This is in reference to the 16"/50 Mark 7 guns on the Iowa class BB.

http://www.navweaps.com/Weapons/WNUS_16-50_mk7.htm

So if my math is right, this works out to .222 MOA?

As modernized in the 1980s, each turret carried a DR-810 radar that measured the muzzle velocity of each gun, which made it easier to predict the velocity of succeeding shots. Together with the Mark 160 FCS and better propellant consistency, these improvements made these weapons into the most accurate battleship-caliber guns ever made. For example, during test shoots off Crete in 1987, fifteen shells were fired from 34,000 yards (31,900 m), five from the right gun of each turret. The pattern size was 220 yards (200 m), 0.64% of the total range. 14 out of the 15 landed within 250 yards (230 m) of the center of the pattern and 8 were within 150 yards (140 m). Shell-to-shell dispersion was 123 yards (112 m), 0.36% of total range.

34,000 yards, means 1 MOA is 35604.7167406844 inches or 989.0199094635 yards, we'll round that to 990 yards. So a pattern of 220 yards is .222 MOA, not bad for a 15 rounds group. Smallest 8 group of 8 is .15 MOA, and the dispersion is .124 MOA.

So the next time someone is saying that they can shoot a .25 MOA or smaller group at 1K+ yards, before you say it's BS, you might ask if he's using a battle ship :)

Far as loadings go, how about a 13,300,000 gr (1,900 lbs) bullet if you like light and fast up to a 18,900,000 gr (2,700 lbs) if you believe in heavy and slower. Charges range from about 2,275,000 gr (325 lbs) for light practice loads, to 4,585,000 (655 lbs) for full power HD and hunting loads.

The D839 propellant grain used for full charges issued for this gun was 2 inches long (5.08 cm), 1 inch in diameter (2.54 cm) and had seven perforations, each 0.060 inches in diameter (0.152 cm) with a web thickness range of 0.193 to 0.197 inches (0.490 to 0.500 cm) between the perforations and the grain diameter.

Now time to find a bigger powder measure, as the Lee one I've got isn't going to meter those 2" long grains real well.

Just found this interesting, especially the relative accuracy of the weapon over the range.

-Jenrick

http://www.navweaps.com/Weapons/WNUS_16-50_mk7.htm

So if my math is right, this works out to .222 MOA?

As modernized in the 1980s, each turret carried a DR-810 radar that measured the muzzle velocity of each gun, which made it easier to predict the velocity of succeeding shots. Together with the Mark 160 FCS and better propellant consistency, these improvements made these weapons into the most accurate battleship-caliber guns ever made. For example, during test shoots off Crete in 1987, fifteen shells were fired from 34,000 yards (31,900 m), five from the right gun of each turret. The pattern size was 220 yards (200 m), 0.64% of the total range. 14 out of the 15 landed within 250 yards (230 m) of the center of the pattern and 8 were within 150 yards (140 m). Shell-to-shell dispersion was 123 yards (112 m), 0.36% of total range.

34,000 yards, means 1 MOA is 35604.7167406844 inches or 989.0199094635 yards, we'll round that to 990 yards. So a pattern of 220 yards is .222 MOA, not bad for a 15 rounds group. Smallest 8 group of 8 is .15 MOA, and the dispersion is .124 MOA.

So the next time someone is saying that they can shoot a .25 MOA or smaller group at 1K+ yards, before you say it's BS, you might ask if he's using a battle ship :)

Far as loadings go, how about a 13,300,000 gr (1,900 lbs) bullet if you like light and fast up to a 18,900,000 gr (2,700 lbs) if you believe in heavy and slower. Charges range from about 2,275,000 gr (325 lbs) for light practice loads, to 4,585,000 (655 lbs) for full power HD and hunting loads.

The D839 propellant grain used for full charges issued for this gun was 2 inches long (5.08 cm), 1 inch in diameter (2.54 cm) and had seven perforations, each 0.060 inches in diameter (0.152 cm) with a web thickness range of 0.193 to 0.197 inches (0.490 to 0.500 cm) between the perforations and the grain diameter.

Now time to find a bigger powder measure, as the Lee one I've got isn't going to meter those 2" long grains real well.

Just found this interesting, especially the relative accuracy of the weapon over the range.

-Jenrick