"...keyholing SEVERELY..." Caused by undersized bullets or an over-sized barrel. Slug your bore.
"...rifles that spent their service lives with cordite..." Cordite was gone by the time your rifle was made. Wasn't used in military ammo after 1904. Not likely by Kynoch in 1952 either.
Kynoch commercial large calibre ammo is sold by Midway. They are loading .303 215 grain SP's though. The yellow box indicates commercial ammo. Doesn't really have much collector value.
"...keep a bottle of Windex handy..." Plain hot water will do. It's the water in Windex that matters. The ammonia does nothing.
"...and nonreloadable..." Maybe, maybe not. Mk VII ammo used both berdan and boxer primers.
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