Well, got the Metford in and fired. It headspaced fine, but with standard 303 FMJ Privi Partizan ammo, it keyholes at 50 yards. It's not a disaster however, as it's been rebarreled at least once - the current time is a SMLE barrel, which apparently is shot out. As I've a basically new SMLE barrel, I'll likely have it rebarreled again, with the goal of making into a #2 sporter.

Update ... I've pretty much solidified on re-barreling the rifle. The bullets used were .312, so they wouldn't normally keyhole. A look down the barrel also shows rifling, but also pitting and wear.

The barrel will likely be a new-ish SMLE No.1 barrel, with express sights, and rust bluing. Haven't settled on the front sight however. The magazine will also be replaced with a No.1 magazine as well. Everything's at the gunsmith now, so more to come eventually.