The rounds were certainly intended for the Browning guns used in RAF fighters that were equipped with .30" weapons. The spec. would have called for the primers to be securely crimped but I think that this was just the way Remington met that requirement.
In 1940 the British Purchasing Commission purchased supplies of .30-06 from two sources. One was Remington and the other was the US Government (before Lend-lease).
Remington initially supplied what was described as “Pattern 06” with a 150 grn. bullet, and the US supplied M1 Ball with FA29 and 30 dates.
Ordnance Board Proceeding 9713 of 4 Dec 1940 gave the results of velocity, accuracy and barrel life for both types, and stated "…Series [of test firings] were also included with pattern 06 ball: it is not intended at present, however, that this pattern should be introduced into the service.
Interestingly, the Brownings used in this trial were serial numbered A1, A2 and A3.
The ammunition purchased by the BPC in 1940 comprised;
From the US Government: .30-06 Ball M1 and .50 Br. Ball and "possibly AP"
From Remington: .30-06 Ball M2, .30-06 Tracer to US specification, .30-06 AP, .50 Br. Ball M1, .50 Br. Tracer M1 and .50 Br. AP M1.
Remington also supplied an experimental .30 AP round with a 153 grn streamlined bullet that omitted the base plug behind the core. They said they could not produce the normal US type in quantity. British tests showed the boat tailed type to be more accurate and equal in penetration to the US type.