Stridsvagn 74 prototype, 1957. Note the odd muzzle brake; as far as I know it was only used on this prototype (#701).
A report from the Royal Military Academy, dated 1960-11-30, regarding live fire trials conducted against a strv 74 turret in August of 1960.
Weapons used:
The report concludes that the 20 mm rounds will reliably penetrate the turret side at distances less than 300 meters, with possible penetrations up to 670 meters. The 37 mm sub-caliber rounds will reliably penetrate most of the turret except an area within 20 degrees to either side of the gun barrel at distances under 750 meters, and may be able to penetrate the gun mantlet at distances up to about 850 meters. The 75 mm sub-caliber rounds will reliably penetrate the gun mantlet with considerable behind-armor effects at distances up to at least 1400 meters and most likely significantly longer distances as well, but that has not been tested.
Archive reference: SE/KrA/0266/002/01:H/F I/43
A few charts showing the effective weapon ranges and possible penetration angles for the strv 81 (Centurion mk 3) and the strv 74 when pitted against the IS-3 and the T-54. The charts have a note on them referring to what is presumably a more detailed description of these estimations but I have not been able to locate that document (yet).
Archive reference: SE/KrA/0266/002/01:H/F I/13
Note that the charts are dated 1957-10-18, but were found in a volume of documents listed as containing documents from 1956.
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Minutes from two meetings at Bofors (on 1954-09-22 and 1954-12-08) discussing the status of various projects. More specifically:
Archive reference: SE/KrA/0266/002/01:H/F I/1
Minutes from a meeting (1954-05-04) at the arms administration’s vehicle bureau regarding the status of current projects. Mentions the “tankette” (project 6400 aka. the KRV), kv 155 (a SPG prototype that would eventually become akv 151 and then eventually bkan 1), lvkv fm/49 (a SPAAG) and the upgunning of strv m/42.
Archive reference: SE/KrA/0266/002/01:H/F I/1
Memo dated 1954-02-17 regarding options for upgunning strv m/42. Mentions both an oscillating turret and rebuilding as a tank destroyer.
Archive reference: SE/KrA/0266/002/01:H/F I/1