S.C. on SMLE barrel

[5thBatt]

Came across this on another forum on a thread about the Ross & British ammo

"The problems with British ammunition were bad enough that a new chamber specification for the SMLE was brought out about the mid-point of the War.

Checking just behind the rear-sights of a number of SMLEs can be an eye-opener. Just remember SC and LC: Small Cone and Large Cone.... and then guess which one might be bigger."

I posted this which is pretty much what is written in all the publications i have, i can find no reference to LC.

"SC on the barrel behind the rear sight means the Small Cone in the chamber has been increased .002-inch
What is LC?"

Got a response (sort of, it was edited on to a existing post) not sure if they are just referring to the Ross chambers or to the SMLE as well.

"All rifles rechambered (to .462") in England were marked "L.C." which distinguished them not only from the original Mk.III rifles with the .460" chamber, but also from those rechambered in Canada to .462" between 9th July and 26th August 1915, marked "N". Those received direct from the factory with the larger chamber .464", were marked "E".

As .462" was the British standard at the time, the "N" probably refers to "Normal" and the "E" probably refers to "Enlarged".

It should be noted that SMLEs were reamed to .464" as well from 1916 on; after the War the standard reverted to .462"."

I see SC on all nearly all my SMLEs behind the rear sight but i have never seen LC & from what i have found SC stamped on a barrel indicates a larger cone.
Comments please.

Information

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[Bruce_in_Oz]

I had some vague notion that the "Short Cone" was at the front end of the chamber and relates to the "Leade".

Early SMLEs (firing Mk6 "torpedoes"), had their barrels TAPER lapped, in an attempt to get muzzle velocities that were much the same as the "longer" L.E. (not so short) rifles firing Mk6.

This involved a LOT of delicate work, ultimately for no real benefit.

The advent of Mk7 ammo tossed all of that out the widow, anyway.

Which raises the issue of the "other" marking that us usually seen with the "SC" job: i.e. "HV". This of course, refers to "High Velocity", being Mk7 ammo.

So, if the "cone" in question is the "forcing "cone"/ leade / throat, then it makes sense to have a shorter cone for Mk7 ammo.

HOWEVER, said "cone" needs to still accommodate Mk6 ammo as this stuff was still abundant and in USE, into the 1930s, even in rifles built at the factory, and sighted for, Mk7 ball.

SO, a comparison of L.E. Mk1, early and late SMLE and No4 chamber drawings is in order.................

To the "Batcave"........................

[5thBatt]

I had some vague notion that the "Short Cone" was at the front end of the chamber and relates to the "Leade".

Early SMLEs (firing Mk6 "torpedoes"), had their barrels TAPER lapped, in an attempt to get muzzle velocities that were much the same as the "longer" L.E. (not so short) rifles firing Mk6.

This involved a LOT of delicate work, ultimately for no real benefit.

The advent of Mk7 ammo tossed all of that out the widow, anyway.

Which raises the issue of the "other" marking that us usually seen with the "SC" job: i.e. "HV". This of course, refers to "High Velocity", being Mk7 ammo.

So, if the "cone" in question is the "forcing "cone"/ leade / throat, then it makes sense to have a shorter cone for Mk7 ammo.

HOWEVER, said "cone" needs to still accommodate Mk6 ammo as this stuff was still abundant and in USE, into the 1930s, even in rifles built at the factory, and sighted for, Mk7 ball.

SO, a comparison of L.E. Mk1, early and late SMLE and No4 chamber drawings is in order.................

To the "Batcave"........................

The SC marking on a SMLE refers to the Small Cone being enlarged by .002inch not the cone being shortened or made smaller, its the opposite.

[Son]

From the LoC, entry 14234 dated 25 June 1908.
Refers to MLM, MLE, MM and ME carbines and rifles

"Shortening of lead from chamber to bore"
In order to better centre the bullet in the bore, and to increase the life of the barrel, it has been decided for future manufacture of barrels of the above arms to reduce the length of the lead from chamber to bore from .8-inch to .6-inch, similar to that of rifles, Short, MLE"

The idea of playing with the leade was not a new one. I am with you in the notion of the short cone refering to a specific design of the leade.

Just found it...

LoC entry 21209 (no date given but is correct for Oct 1918)

Rifles, short, MLE
Rifles, Magazine .303-inch
pattern 1914 fitted with the
model 1918 telescopic sight

Modification of small cone of cartridge chamber barrel.

It has been approved for future manufacture that the diameter of the small cone of the cartridge chamber of the barrels of the above mentioned rifles will be increased by .002-inch.
For the purpose of identification, these barrels will be marked "S.C." in the position stated here under-
Rifles, short, MLE. -On the barrel, behind the backsight.
Rifles, magazine, .303-inch pattern 1914, &c. - On that part of the barrel exposed in the nosecap opening.

[Mk VII]

The small cone is what Americans would call the shoulder.

[Bruce_in_Oz]

That clears that issue up, but what was going on that the "shoulder" needed adusting?

Was it something to do with providing clearance for "mud" or dubious wartime ammo? Being a rimmed round, you can have a "generous" shoulder, and even body clearance (instant "improved" cases), and no problems with headspace / striker protrusion, unlike a rimless model in which length from head to shoulder datum is critical..

As a side note, what is the source of that illustration?

Back to exploring the crypt for the various .303 chamber drawings.

Does anyone have barrel / chamber drawings for Bren and Vickers, as well.

There seems to have been a lot of creative engineering in these regions for a long time, but even drawings for 7.62 NATO barrels show subtle differences between machine gun and rifle chambers.

[Surpmil]

That clears that issue up, but what was going on that the "shoulder" needed adjusting?

Was it something to do with providing clearance for "mud" or dubious wartime ammo? Being a rimmed round, you can have a "generous" shoulder, and even body clearance (instant "improved" cases), and no problems with headspace / striker protrusion, unlike a rimless model in which length from head to shoulder datum is critical..

As a side note, what is the source of that illustration?

Back to exploring the crypt for the various .303 chamber drawings.

Does anyone have barrel / chamber drawings for Bren and Vickers, as well.

There seems to have been a lot of creative engineering in these regions for a long time, but even drawings for 7.62 NATO barrels show subtle differences between machine gun and rifle chambers.

In regard to your first question my thought would be that a tighter cone would help to center or align the case in the chamber, and therefore the entry of the bullet into the rifling - assuming of course that the bullet and case were in fact aligned during manufacture!

[Son]

There seems to have been a lot of creative engineering in these regions for a long time, but even drawings for 7.62 NATO barrels show subtle differences between machine gun and rifle chambers.

I find the whole idea of (for example) the 7.62 x 51 chamber being 41.40mm from the bolt face to the centre of the shoulder (accepted as the point where the headspace measurement is taken) being set by some organisation like saami as ridiculous. Sure, you can standardise the cartridge case to a fair degree, but the manufacturers have always dictated the size of their chambers and have gauging to match. In my gauge kit I have no less than a dozen different sizes of 7.62 NATO headspace gauges. It comes down to what the firearm's intended use and method of operation is.

[Bruce_in_Oz]

Son,

Yes, I noticed that as well:

The different "5.56 NATO" gauge sets for M-16A2, M-4, F-88 and F-89 are testament to that. The differences between the chambers for the M-16 and the M-4 are subtle, but obviously there for a reason.

In the "old" days, we had different "7.62 NATO" gauge sets for L1A1, M-60, Parker-Hale and L-4.....and then the MAG 58s arrived with THEIR own gauging for the same "nominal" cartridge and chamber..........a thou' here, a thou' there, and a new set of NSNs to keep track of.

We didn't get the L-42 here, but I was intrigued about a story that they were "headspaced funny". something about a VERY close fit; oddly enough, something you can do when you have a rimless case AND an action with helical locking. Any enlightenment on that one??

[Peter Laidler]

The L42 and 39's were a very tight CHS simply because of what they were and in real terms, there was no heat to consider (well, there was but nothing to write home or get worried about). 7.62mm CHS gauges were a nightmare and once the marking wore off, identifying the various gauges was a real problem. I had the calibration gauge so at least ours could be sorted out.