Artillery Evolutions: More French – Grande Puissance Filloux

Can we say that without getting a mature rating?  Sure!  Grande Puissance Filloux is the “friendly” name given by the French to the “Canon de 155mm mle 1917 G.P.F.”  In the last Artillery Evolutions post, I mentioned the French 155mm gun pressed in to service by the American Expeditionary Force (A.E.F.) during World War I.  This wonderful cannon became the basis for later American designs, vestiges of which are still seen on current service types.

Canon de 155mm mle 1917 G.P.F.

This particular make of gun came about due to the shortage of heavy field guns in the French inventory at the start of World War I.  In the void, the French pushed several expedients into service.  These ranged from ancient guns dating to the 1870s to more modern seacoast guns, in calibers ranging from 145mm to 155mm. The better of these guns was a 145mm seacoast gun mounted on a field carriage.  While providing a useful range over 20,000 yards, the 13.5 ton weight was cumbersome for a field gun.  Here’s a Canon de 145mm mle 1916 in action, but under new owners, circa 1942.

Canon de 145mm mle 1916 in German Service

During World War I, many of these returned to the shop with worn out barrels.  The French in turn rebored these to 155mm, conforming to the standard field caliber, and increased the range to over 23,000 yards.  While the French were happy with this heavy weapon for the static warfare of the Western Front, they looked to more mobile heavy artillery piece.  In an effort to improve the field handling, the government run Puteaux arsenal started work on a fresh design in 1916.  Part way through the project, Lieutenant Colonel L.J.F. Filloux pushed for a split trail carriage in order to allow higher angles of fire, wider arcs of traverse, and easier handling.  As result of his successful argument on this point the gun became the “High Power, Filloux” or “Grand Puissance, Filloux” gun, abbreviated to G.P.F. when the type was adopted in 1917.  On the carriage, the gun had an elevation up to 35° with a traverse of 60°.  Overall the gun on carriage weighed just under 10 tons.

G.P.F. in American use showing split trail and elevation

Aside from the carriage, the gun used rather conventional practices.   The breech and firing mechanism used was the standard Schneider type and similar to that of the 155mm howitzers.  The barrel was a built-up construction, externally appearing as an enlarged 75mm gun.  The recoil mechanism was also similar to the 75mm, but with a new twist – variable recoil.  At the maximum elevation, a conventional recoil system allowed the breech to bottom out.  Other guns of the time period required the crews to dig out a pit in order to deal with this problem.  What the G.P.F. introduced was a system to automatically adjust the resistance in the recoil system as the gun was elevated.

That’s the concept.  In use that meant the crew didn’t have to dig a pit for the gun.  And they could even put down some planking out to keep out of the mud(!).  Although I would add that some diagrams in the manuals still indicated pits were used.

American M1918 155mm with firing platform

For movement, the G.P.F. used a two wheel limber.  In traveling order, the setup weighed about 11.5 tons.  While heavy, still handier than contemporary weapons of the caliber.  The recoil system disengaged to allow the breech to ride closer to the limber.

G.P.F. in traveling order with "caterpillar" shoes

In the photo above, the guy at the front is not driving the gun.  Rather he’s handling the brakes.  The G.P.F. was perhaps among the first artillery pieces designed with mechanization in mind… but air-brakes were a thing of the future.

Although the G.P.F. introduced several advanced features, it’s range dropped to 17,700 yards when compared to the earlier 155mm mle 1916 mentioned above.  In order to improve field handling the G.P.F. sacrificed range for a shorter barrel and lower maximum elevation.  On the other hand, with ten times the traverse, a G.P.F. could command significantly more battlefield than the earlier gun.

The French built over 700 of the G.P.F. guns starting in late 1916.  The combat debut occurred in August 1917.  The gun’s arrival coincided with America’s entry into the war.  Starting in September 1917 the French supplied quantities of the G.P.F. to the A.E.F.  By the time of the armistice, the A.E.F. received over 200 French built guns of this type. The guns supplied by France became the M1917 155mm field gun in American use.  I think the example displayed at the Ordnance Museum (was at Aberdeen, Maryland, but moving to Fort Lee, Virginia) is one of those guns.

M1917(?) 155mm Field Gun at Aberdeen, MD

But of course with the massive American buildup, French sources would be insufficient for war plans extending into 1919.  So just as with the other French guns, the Americans opted for domestic production.  In 1917 the Ordnance Department translated French plans and tabulated them for American standard measures.  In November 1917, the Army set contracts for production a couple thousand of these guns, broken out – as we’ve seen with other guns – into sub-components.  Watervliet Arsenal and Bullard Engineering Works produced the gun tube; Minneapolis Steel & Machinery Company produced the carriages and limbers; and Dodge Brothers produced the recoil components in a Detroit factory.

155mm Gun barrels in the factory

Like the smaller guns, G.P.F. production lagged due to difficulty producing the French recoil system.  However, the Army had ordered Dodge to put priority on the howitzer component production through 1918.  So by the time they turned to the G.P.F. most of the kinks were worked out, but the first rolled out of the factory in October 1918. Thus many American-built G.P.F. guns were fitted with French built recouperators.   Production of the carriage slowed as Americans had to adapt factories to the large castings required.  But the gun tube itself speed through production.  The Americans actually improved the design, adding a better system to lock the jacket in place and a spring operated breech mechanism.  As built, this became the M1918 155mm Field gun.

M1918 155mm Field Gun at Fort Morgan, AL

With the delays, only sixteen complete American-built guns got to the A.E.F. before the Armistice.  But, impressed with the gun’s performance, the Americans kept the gun in production into 1920.  Not only was the gun deemed the best corps level gun, it was also found useful for the coastal artillery.  In the inter-war period, the Army built “Panama Mounts” to allow these field guns to defend coastlines, particularly in overseas possessions. The gun also received pneumatic tires and air brakes on an improved carriage.

A G.P.F. gun on a Panama Mount during World War II

The Army would further refine the G.P.F. concept during the inter-war period, with the familiar M1 and M2 series as the result.  During World War II, several M1918 guns went onto a modified medium tank chassis to become the M12 Gun Motor Carriage.  But the G.P.F.’s long reaching legacy was a carriage layout which persisted in American artillery down to the M198 155mm howitzer.