This is ammunition made by the Dominion Arsenal, which was the Government ammunition factory. It is Berdan-primed, corrosive and mercuric and charged with Cordite MD-T 5-2. In ordinary language that is Cordite Modified Tubular with the tubes measuring .05 inch on the outside with a .02 inch hole down the centre. It is an exact copy of the British powder and was loaded again in its billions until the end of the .303 era with only a couple of years of final production of a more modern powder. It moved a 174-grain flatbase .312" bullet which was of 3-piece construction: jacket, small nose packing of some lightweight solid material and a lead-antimony filling. Muzzle velocity in the SMLE rifle was close to 2440 ft/sec and in the 30.5-inch Ross barrel about 2650 ft/sec. It was very accurate and, just as a bonus, impact-unstable.
At the time these rounds were being made, production was starting-up at a SECOND Government plant at Lindsay, Ontario, the Lindsay Arsenal, which used LAC for its initial headstamp and switched quickly to DAL.The Lindsay Arsenal, being built in Sir Sam Hughes' riding, was in the middle of a firestorm of political controversy and was shut down at the conclusion of the War, then sold off in 1921.
Ammunition was also made FOR the Government by the private commercial Dominion Cartridge Company and bears the headstamp DC.
Canadian ammunition was always strictly to specification and played no part whatever in the lengthy, expensive and deadly ROSS Rifle controversy. The Dominion Arsenal ammunition was some of the very BEST produced during the Great War.
It is not unusual to find the odd single round at a gun show, but coming across a QUANTITY which has been stored in a single unit for the past 104 years is really something else! You are a Lucky Guy!
Thanks for letting us drool at your good fortune!
