gomer
A conical chamber at the breech of the bore in heavy ordnance, especially in mortars.
[Table] of dimensions of howitzers, stone and Gomer mortars, vol. 1. p. 250.
Where it comes from
After Louis-Gabriel de Gomer, the French artillery officer who invented the design. Attested in English since the early nineteenth century.
Adapted from the Wiktionary entry gomer (CC BY-SA 4.0).