timmy wrote: ↑Thu Oct 14, 2021 6:57 am
Cordite as a smokeless propellant came in different formulations.
Cordite is a double-based powder, which means that its major components are nitrocellulose and nitroglycerin.
Single based powders only have nitrocellulose as a major component, and tend to burn cooler than double based powders.
Cordite, as originally formulated, was sensitive to temperature variations and, if impurities crept into its manufacture, could become unstable and prone to detonating at inconvenient times.
One thing that must be understood about these smokeless propellants is that they
DO NOT explode -- they burn. This burn rate isn't a fixed value, either. Pressure affects burn rate, so that in unconfined burns, they can sometimes tend to "fizzle", while when contained in a cartridge inside the chamber of a firearm, they can burn much faster.
Compare the 30-06 cartridge with the 300 H&H (sometimes called "Holland's Super 30"): When the 300 H&H was first brought out in 1925, its reason for existence was not to provide a more powerful "magnum" load ("magnum" is just a word for a rather large wine bottle!). The 300 H&H was intended to provide 30-06 ballistics in every corner of the British Empire, without its cordite charge being affected by the heat of tropical and semi-tropical or desert conditions (which will raise the working pressure of a fired cartridge). The cartridge was designed with a gentle taper to provide easy extraction under all conditions. Because of the gentle taper, the 300 H&H didn't have the ability to headspace (determine the correct position and fit of the cartridge to the chamber) on the shoulder, just as its parent, the 375 H&H didn't. So, headspacing was determined by the "belt" on the base of the cartridge. The belt was used, rather than a rim, like the 303 had, because rimmed cartridges don't always feed well through bolt action repeaters. The belt enabled the 300 H&H to slide over the cartridge beneath it in the magazine without "rim interlock" jams, while retaining the headspace function similar to a rimmed round.
Soon, folks began to realize that, with powders more modern than cordite, they could obtain faster velocities than the 30-06 provided with the same bullet because of the larger case capacities. This larger case then was called "magnum" (like the large wine bottles) and the sign of a magnum cartridge was the belt, something that was completely superfluous in the later cartridges formed from the 300 H&H case, like 300 Weatherby, 300 Winchester Magnum, and 7mm Remington Magnum. It has only been recently that cartridges have been designed with the diameter of the belt for the length of the cartridge body, allowing even more powder capacity, sometimes in a shorter case.
Unless you have a 375 or 300 H&H, good riddance to the belt! It's not needed! To the "hillbilly" crowd, it symbolized an extra-powerful cartridge, and others thought that it added strength to the case head (which it didn't), but it was simply a leftover from the 300 and 375 H&H cartridges that furnished the cases from which later "magnums" were formed. (I won't comment on the need for cartridges other than 300 and 375 H&H, except to say that I like the 300 H&H very much.)
Famously, the unstable nature of cordite as a propellant was vividly demonstrated at the Battle of Jutland in WW1, where German shells blew up three British Battle Cruisers, each time with the loss of almost all of their crews. This catasrophe was laid at the foot of Admiral John Fisher, whose "brainchild" the Battle Cruisers were, the reason given being that Fisher had the ships designed without enough armor.
The fact of the matter is that British admirals stressed rapid rates of fire, which cause the British to store the extra munitions needed unsafely, filling turrets and passageways with bags of cordite. Hot metal and sparks from German hits ignited these mis-stored charges and, like a trail of powder in the movies, fires led from the turrets to the magazines below.
The Germans, with their more stable single based powder also suffered hits, but, as with Seydlitz at the Battle of Dogger Bank, even destructive fires did not destroy their ships.
But since all of the British high command subscribed to the doctrine of rapidity of fire and the careless storage of propellent that went with it, they could hardly tell the British public that the loss of thousands of their sons, brothers, and husbands was due to their admirals' bungling, it was found better to lay the blame on Fisher (who most of them didn't like anyway) and his ships. Truly, a poor mechanic always blames his tools.
By WW2, the British had largely sorted out their cordite issues.
It is true that the temperature of ignition can burn out barrels, especially the area in front of the chamber. Also, rapid firing without letting a barrel cool down can accomplish this, too. Reasonable care taken while shooting can avoid this, although I will confess that I don't know what IOF uses in their cartridges for propellant -- they may jam cartridges full of crumbled Chinese fireworks, for all I know. But generally, modern ammunition should permit a barrel life of a thousand rounds or more, depending on the intensity of the cartridge the powders used, and often a 30-06 Springfield US Army rifle was said to have a barrel life of 10,000 rounds. That's a lot of shooting!
Regarding the IOF 315, it is a modified SMLE No. 1 Mk III*, with all that this implies. The later upgrade of the No. 1 Mk III* was the No. 4, introduced just before WW2. These were used for sniper rifles. But the really accurate British 303 bolt action rifle was the Enfield Pattern 1914, which was produced in great numbers for the US Army after being rechambered in 30-06. This got around the accuracy problems of the SMLE, which chiefly was concerned with the bedding of the fore stock.
The critical areas of SMLE fore stock bedding are the two bedding areas beside the trigger slot and the proper fit between the rear of the stock and the butt socket. Often, wood that has shrunk causes poor bedding in these areas, to the detriment of accuracy. These are things that a good gunsmith can address in either a SMLE or and IOF 315, with the use of a properly bedded stock.
But stock issues, while they can be addressed, can't totally compensate for the basic design of the rifle.
Unless one is mounting a scope, at practical hunting ranges, I can't see one being very disadvantaged by hunting with an IOF 315, compared to other rifles. But on the range, this is another matter. Still, it does depend on the sort of competition. I have seen videos of Norwegian rifle competion, where in timed fire, the old Krag rifles rivaled semiautomatic 30-06 Garands for rapid, accurate fire. The legendary smoothness of the SMLE would be an advantage in such competion. It would be a diffent matter for other forms of competition, however.