Whoever mentioned a 7.62 magazine for their DCRA conversion rifle has misunderstood the conversion concept. Britain was the only country seriously attempting to magazine feed 7.62 into No.4 receivers, whether as L42A1, Enforcers or Sterling conversions. The Envoys and L39s were single loaded target rifles.
In the 1960s and 70s after Canada switched to NATO ball ammo, there were two choices for Bisley-type target rifles. Many shooters sent their #2 rifle off to CAL or one of the approved gunsmiths to have the barrel, extractor and bolt head changed. The rifles were fired single-loaded at 300, 500, 600, 800, 900 and 1000 yds. Two sighters, seven or ten on score, with two shooters firing alternately. The rules did not require feeding from a magazine, so guys would drop one lovely DA 64 round after another onto the original .303 follower like a loading platform. When their #1 .303 began to disappoint, the shooter could send it off to be converted, or more often than not (because there was never a great deal of money to idly chase unsure bullseyes), they'd go over to a purpose built target rifle, either a P14/M17, a Mauser 98, a Carl Gustav, a Rem 40 or 700, a Win 70, a CIL, a Musgrave, or later a Sportco. The conversions quickly lagged behind as uncompetitive. For converted military rifles a magazine well was a liability, a weakness in the receiver compared to tubular receivers.
The DCRA's rules were generous, and it was a time of progress in leaps to move beyond military pattern rifles. The No.4 conversions were just not going to earn the shooter a place on the Bisley team. The qualifier to that was when IVI ammo came along, and it was awful! For some black-magic reason, some No.4 conversions with short stiff free floated Envoy barrels had a sweet spot trajectory flip that held the scoring rings better at 800, 900 and 1000 and beyond. My father's had a hogged out No.4 foreend and an unfinished high comb stock. Guys had their short range rifles and their long range rifles. The arrival of crowbar stiff Swing, Angel, RPA and Paramount receivers cleared up those leftover bit of McGuivery.
To conclude, a DCRA rifle was never intended to be a magazine fed repeater.