As to the wild tales of boat-tailed bullets not shooting their best in Enfield barrels, that came from the guys at the Royal Small Arms Factory at Enfield. They experimented with boat-tailed bullets and found that rifles generally shot more predictably with flat-base, which is part of why they stepped up the powder/power/pressure levels when they developed the Mark VIII loading for the Bren and Vickers Guns, BOTH of which had locking mechanisms much stronger than the Lee action has.
Around here, my shooting buddy and I have been playing with old military rifles since 1982. I know, this is merely 28 years. But our findings are that you can get ANY rifle which uses Enfield rifling (equal-width lands and grooves, odd number of grooves/lands) to shoot AT LEAST as well with flat-based bullets, as you can get it to shoot with boat-tails. Often, the difference is amazing.
Obturation, obviously, must be a part of it. But we also have been obtaining identical results with Australian, British, Canadian and American barrels ranging in condition from well-used, right up to 'mint - unfired' until we got our hands on them. Rifles tested include a 1918 NRF SMLE in very close to perfect condition, barrel perfect.... also a 1918 Lithgow which was literally unfired when we started, several P-'14s and a whole slew of P-'17s, several of them with VERY serious glass on them as well as a couple of VERY minty Number 4s.
Perhaps 28 years at this particular series of tests isn't enough but, when I see Enfield rifling, I reach for the flat-based bullets because I KNOW that I can get them to shoot WITHOUT screwing around five-eighths of forever. I'm lazy. Also cheap.
Wide-groove Mauser rifling...... now, that's a whole different ballgame and this is where your boat-tails have a distinct advantage.
But not in Enfield rifling.
Sorry, but that's just the way I see it.
