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

Question for all the knowledgeable Lee Enfield rifle worshippers :

What is - or was - the ballistic coefficient of the 174 gr. flat-base pointed bullet used in the 303 British Mk VII ammunition ?

I can read on Wikipedia that the ballistic coefficient is supposed to be .467 but that's all what I have been able to find - and, yes I tried to find the answer to my question here on Military Surplus Collectors Forums but unsuccessfully, up to now.

Well, Wikipedia might be right - and then, might be wrong too.

Quote:

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Originally Posted by Snowy Owl

the ballistic coefficient is supposed to be .467

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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.

Does Hatchers give the answer. It must appear in the Textbook of Small Arms somewhere although as an Armourer, any chapters relating to ammunition, I staple together!!!!!!!!!

Without digging out Hatcher again, I think he notes that the British 1929 tables in the Textbook are based on a different set of firings and a different standard projectile from the Krupps-Mayevski firings of 1881, so the BC for these tables will be different.

Quote:

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Originally Posted by Patrick Chadwick

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.

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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.

I'd guess that the .468 number is close enough for most purposes. The 180gr Sierra hunting bullet is rather shorter as it doesn't have the plug in the front of the bullet found in the Mk.VII. The SP bullet's ogive and nose are blunter. But the 180gr Sierra still matches the military ball's flight characteristics with in a minute or two out to 700 yards, based on shooting them through No.4 Mk.I (T) rifles.

Quote:

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Originally Posted by jmoore

I'd guess that the .468 number is close enough for most purposes.

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Agreed. The Sierra ballistic tables show the difference in drop at 300 yards (for the two types I quoted, at 2600 fps) as being about 1". If you can tell that differenced shooting a milsurp, you shouldn't be wasting your time reading our ruminations, but out there collecting your international medals, as that difference amounts to about 0.3 MOA.

So unless you are intending to shoot at 1000 yards by dead reckoning, with a benchrest rifle, I really doubt that knowing the value to 3 figures matters at all.