Ballistic coefficient of the bullet used in the 303 British Mk VII ammunition ?

[Snowy Owl]

Could be, but it seems a trifle high.
In my old Sierra Rifle Reloading manual (50th Anniversary Edition) I find:
.311 / 174gn HPBT MatchKing, with

.499 at 2200 fps and above
.493 from 2200 down to 1800 fps
.480 below 1800 fps

and
.311 / 180 gn Spitzer, with

.411 at 2000 fps and above
.407 from 2000 and 1600 fps
.407 below 1600 fps
(that the last two are identical seems unlikely - maybe someone can check these figures?)

I would expect the value for the Enfield projectile to be noticeably lower than for the HPBT, and much closer to the "spitzer" values.

And now, just to muddle things up a bit more, I found that Speer is making a .311 / 150 gr. Spitzer SP bullet with a ballistic coefficient of 0.411 - sectional density .222 (Part Number 2217).

The sectional density of a .311 / 174 gr. bullet is .257, by the way. If really a .311 / 150 gr. Spitzer bullet has a ballistic coefficient of 0.411 with a sectional density of .222, then, logically, a .311 / 174 gr. Spitzer bullet with a sectional density of .257 should have a substantially higher ballistic coefficient.

Moreover, it seems to me that the ogive of the Mk VII bullet is significantly longer than the ogive of the Sierra .311 / 180 gr. Spitzer bullet.

Somebody, somewhere, must have the answer - hopefully.