Fultons of Bisley; Enfield accuracy secrets revealed. (By RJW NZ)

[Bruce_in_Oz]

There is also another major fly in the ointment here.

Ammunition. As I see it, the No1 was originally built around the Mk6 cartridge. I understand that there are several differences in and around the barrel, between a mk1 and a Mk3 / 3*.

And then the ammo was changed to Mk7, a radically different projectile weight and shape. The rifles had to be tuned to the ammo, not the other way round as per the "sporting" world.

So, if your rifle is bedded by the book, it was probably bedded for Mk7 ammo. As soon as you start feeding it anything else, all bets are off.

One problem that occurred was that pretty much for the life of the SMLE, the barrels were throated for the old round-nosed projectile, not the slinky Mk7. Freebore, anyone?

The No4 barrel seems to be a little different, if the drawings I have seen are an indication.

No1 barrels have a leede of 0.600 inches; quite long, but capable of handling Mk6 ball.

The No4 throating is defined differently and the reference to a diameter of .300" Basic is really odd, given that bore spec on the same drawing is .301-.304" with a groove diameter of .313" to .319" (fairly "agricultural" by today's barrel making standards).

The bullet leede is essentially a 5 degree included taper starting at the forward end of the short cone in front of the cartridge area.

I'll stuff it into CAD and see if I can come up with a printable comparison drawing of that area.

And it would be interesting to compare it with Bren and Vickers chamber specs.