peeved wrote:AA barrage use with time fuzed ammo?
Excellent peeved, that is exactly the right answer. Anti-aircraft use by using mortar shells equipped with tracers and time fuses. The report calls the resulting weapon as 120 it.krh (120-mm anti-aircraft mortar).
In my last visit to the archives I happened to find a report according which Finnish Army was testing 120 Krh/40 mortars equipped with thicker barrels for anti-aircraft use in May - June 1944. Colonel A.E. Saloranta sent the particular report to Colonel Helminen in 2nd of June 1944. According the report the early experiments seem to have been quite successful - with increased propellant charges they reached muzzle velocity of 400 m/sec with normal mortar shells without facing any real issues with ammunition or mortar. Admitted number or shells fired was quite limited and real durability was not yet tested at that time. At 70-degree angle this allowed the mortar shells to reach ceiling of 4,000 meters in distance of about 3,000 meters from the mortars. The report suggest acquiring four such mortars and giving them to suitable Air Force unit for further testing and according report Salovaara had already unofficially ordered the mortars from Tampella for the purpose.
The intention was to first use modified French fuses and actual mortar shell used for the purpose would have been a version especially designed and manufactured for it. The time fuse was to have three settings - 12 seconds, 10 seconds and 28 seconds. With variety of propellant charges there were expected to provide suitable solutions for shooting at heights of 1,000 - 4,000 meters. Tracer should have been activated 10 - 12 seconds before the shell would detonate.
My own opinion is that the performance wasn't exactly spectacular (for example 40-mm Bofors had ceiling at 5,000 meters and maximum range of 9,000 meters) and the actual chances of hitting an aircraft extremely poor (even heavy anti-aircraft batteries with their powerful purpose-built guns, rangefinders and mechanical computers had hard time doing that). What ever happened, the concept never saw large-scale use. The origins for the idea also remains uncertain - it may have originated from Colonel Peura whom Saloranta consulted about the concept, but in Tampellasta Patriaan/From Tampella to Patria by Vesa Toivanen also mentions in page 50 that Tampella staff apparently considering using 120-mm mortars as improvised anti-aircraft weapons with mortar shells equipped with time fuses during Continuation War.
Those wishing to read the original report (it's in Finnish), I made it temporarily available:http://www.jaegerplatoon.net/_AA_mortar1.jpghttp://www.jaegerplatoon.net/_AA_mortar2.jpg
Over to you peeved.