Others on the forum more knowledgeable than me have suggested in previous posts that the Livens projector was very effective and that the high tensile steel required for the tubes could only be manufactured in sufficient quantities by the British.
I hate to "pile on " White Star", but the comment about especially high tensile steel being required for the Livens projector is a puzzlement. (I amn a mechanical engineer and am intensively studying and writing about German super-heavy artillery .) A weapon of that general design has, I believe, rather low breech pressures. It was possible to make weapons similar to the Livens projector with wooden barrels bound with steel straps, I believe. I have a photo of my fathers' of an emplacement of German weapons along the line of the Livens Projector, set up to deliver gas; my father had offered a copy to the West Point Museum, which responded that they were interested as they did not have a similar photo. I know of a somewhat ballistically similar weapon often made with PCV pipe, hardly high-tensile steel. But it is true that the Germans had some difficulty obtaining certain exotic metals used for hardening alloy steels, due to the blockade. Remember that, pre-war, the Royal Navy and every other major navy paid Krupp a royalty for every ton of armor plate incorporated in capital ships. They hardly were innocents in the manufacture of alloy steels.
I believe that some German guns, in particular the "Paris Gun" and the Gamma=Gerat
42 cm howitzer, had breech pressures in excess of any Allied artillery. The former had sufficient breech pressure to toss a 21 cm shell 40 miles up and 80 miles out, wearing out the barrel in about 80 shots, despite employing a set of shells of graduated diameter to make up for barrel erosion. At every shot a device in the wall of the chamber measured the actual breech pressure of that shot, for adjusting the next powder charge. A small piston struck and deformed a steel ball, that ball then put in a special calibrated microscope to measure the deformity and hence the breech pressure.