The US WWII M1 "Long Tom"

Today we're looking at the US 155mm Long Tom. Within this series of guns, there's about four different sub-variants. The first one being the M1, the M1A1, the M2, which this one is, and the M59. This gun went into development in the 1920s and 1930s to replace the French 155 GPF gun, which the Americans were using up till about 1941. So in the 20s and 30s, a few designs and prototypes went ahead. They come up with a prototype called the 155mm T4 on carriage T2, which was then adopted in 1938 as the 155mm gun M1 on carriage M1. This is referred to as a gun, so it has a longer barrel at about 45 calibres long. So this gives us a long range of fire at a flatter trajectory, where if we look at this piece over here, which was the 155mm M1A1, later referred to as the M114, this is classed as a howitzer. So this is a shorter barrel, higher trajectory. The class of a howitzer is measured in calibre, so it's anywhere between 15 to 25 times the calibre length, which would give you this barrel, and this comes in at about 24.5 calibres long. The carriage itself comes in two different variants, the M1 followed by the M1A1 carriage. At the front, we've got two axles, two sets of tyres on each. A nice feature about this gun is these bogey adjusting screws just here. The crew have an adjusting spanner, and they wind these down, and it lowers the carriage onto the ground, which gives us that stable gun platform. It's like most artillery pieces, they're carried by limbers. So early on in about 1938, for the M1, we had the M2 limber. So this is essentially two wheels, and it had a mechanism that could lower it straight down to the ground. Later on, we come with the M5 limber, and this was used with a sling that could lower the trails to the ground. The only problem with this is when they lower the trails, these spades have got to be dug into the ground, so that can actually come up and lock in, and then this pin locks the actual spades into the trail. This has interrupted threads, designed by a French fella called Charles de Bange in 1872, further improved by Axel Weyland in 1890. Now when we get to our gun, this was further improved by a fella called Dorsey Asprey, and a United States Navy officer, Lieutenant Commander George Smith. They incorporated a vertical sliding handle, which allowed the breech to be closed and opened using one motion. Open up, and then they would literally pull it across, and it would lock as threads in one motion. Now the difference between the M1 and M2 was that the M1 had a sleeve that was fitted in this area here, and on that sleeve is where these female threads were cut in. When we go to the M2 variant, which our gun is, it didn't have the sleeve, but the threads were actually cut into the breech ring itself, and the M2 chamber for where the powder goes in was much larger than the M1. Recoil system on this gun is hydropneumatic. Because it has a high angle of elevation, they can actually control the amount of recoil on this gun. There's seven different charge bags that they can use. On full charge, this gun will recoil 70 inches. They have these cylinders up the top here, so one either side of the gun. These are the equilibrators. So these are nitrogen-filled, so they are under pressure, and this allows the gun to be held through all angles of elevation. One of the gunners sits on the left-hand side here, so this is the bracket M18. It can be fitted with two types of panoramic sights, one being the M12 and then the M5A5. So this sight sits in this bracket here. It's offset to a 45 degree angle, and this allows this gunner to remain out of the way when the gun recoils. So we've just come over to the 203mm variant of the 155. It has the same platform, but this one, unlike the 155, has the gunner's quadrant. So this is for elevation. This is the mount M1, and you have the M1 quadrant piece that sits in here. So this will allow the gun to elevate to plus 63 degrees, and it will go down to minus 1.3 degrees. So it goes actually below horizontal. With this traversing handle, which we're obviously missing on this one, you can see the traversing mechanism here. So this can traverse 30 degrees left and right. If we look at, say, the 25-pounder, it's got a circular platform that it sits on. This also has the same type of device. Now this is at about 11.2 metre diameter around. The centre of the gun sits on that. The end of the trails sit on the outer ring of the platform, and the gun can be turned around 360 degrees. So the first type of ammunition that we can fire is an armour-piercing round. This has a muzzle velocity of about 836 metres per second. That can fire it out to a maximum range of about 22,000 metres. This AP round is said to be able to penetrate 191mm at 1,000 yards, or about 914 metres. Second one is the HE round. So this has a muzzle velocity of about 856 metres per second, and that can fire this one a little bit further, to about 23,500 metres. It's not here at the moment, but this gun can actually be fitted with what's known as a sub-calibre bracket. So we have the T-10 bracket, and it can be fitted with an M1916 37mm barrel. It can actually fire a sub-calibre projectile without having to use the main gun. So this is in aid of training. Excellent piece to have in the museum, along with the 203mm variant. So this gun was used by at least 16 countries, including Australia, and Australia did use these against the Japanese in New Guinea in 1945.