17 November 1943 Part 2

17 November 1943 Subsequent assessment of the Mirus gun failure

Undated subsequent assessment of the 16–30 November diary concerning the proof firing of Mirus No. 3 gun on 17 November. Secret. For the Commanding Admiral Channel Coast, Chief of Staff.

After repairs involving installation of a filling cylinder and a horn ring with carrier, No. 3 gun was proof-fired on 17 November 1943. On the third round, two litres of fluid were released and a further recoil test was made to distribute the air.

Shortly after completion of the recoil, the same fracture between the carrier and horn ring occurred again. In the opinion of the Krupp representative, subsequent reinforcement of the horn rings was impossible. Unless the pressure in the filling cylinder could be reduced, four newly designed horn rings would be required. The renewed fracture of the carrier at the horn ring of No. 3 gun showed that the carriers on the other guns were also insufficiently strong to withstand the high pressure.

It therefore had to be feared that the same defect would recur in the other three guns during the next calibre-practice firing. In the worst case, the whole of Batterie Mirus could fail permanently at the outset of an enemy attack, rendering futile the enormous expenditure upon the heaviest and most important battery in the Channel Islands.

It was therefore considered urgently necessary, independently of any further replacement of the carrier on No. 3 gun, to place an expedited order with Krupp for four new horn rings with carriers.

Later handwritten annotation, undated: “Modification carried out by strengthening the horn rings.” This annotation is distinct from the typed assessment, which says that the Krupp representative considered subsequent strengthening impossible.

T-1022 Roll 2422, scans 0731.