The SK-46 was one of several post-WWII experimental self-loading rifle designs developed for testing by the Swiss military, or for commercial export. It was manufactured by SIG at Neuhausen in both 7.5mm Swiss and 8mm Mauser. The rifle is gas operated, with a rather complex tilting bolt action. It uses 5- or 6-round detachable box magazines much like the K-31 bolt action (the magazine capacity depended on caliber; 8mm was 5 rounds and 7.5mm was 6 rounds, to match the common clips/chargers used in each caliber).
One interesting element of the design was the use of a charging handle made to mimic the appearance and function of a traditional bolt action rifle. A similar approach can be seen on the German MP-35 submachine gun and G-41(M) rifle. The SK-46 also incorporated a standard rail for attaching a 2.2x optical sight (not present on this rifle).
“(the magazine capacity depended on caliber; 8mm was 5 rounds and 7.5mm was 6 rounds, to match the common clips/chargers used in each caliber).”
A.B.Zhuk states it have magazine for 6 or 12 cartridges (7.5mm) and 10 cartridges (7.92mm)
That would make more sense for a post-WWII semi-auto rifle. A 5 or 6 round magazine would have meant a LOT of reloading pauses for firing.
That would be true if you were talking about someone in the middle of a street battle. But if the user were a designated marksman or sniper not in the middle of a shootout, would the magazine size matter? Give this thing a shaded scope and a suppressor, and it might be good for trolling the other team from within the deep dark woods… Or am I wrong?
As for the option of manual cycling, it’s obvious that the charging handle in the horizontal position is in the same configuration as the bolt handle on a K31. Having the charging handle on the side of the bolt rather than on a bolt carrier around the bolt seems awkward but handy in that the assembly in “manual” mode isn’t immediately sprung out at the user during field stripping (again, this is only an assumption).
Notice that the basic design is more or less “a modification of a standard infantry rifle.” Why create a radically new base platform design when you can modify an existing platform? The unusual setup can therefore be considered an attempt to make a decent bolt-action rifle into a decent semi-automatic rifle requiring more changes to the receiver than the stock, barrel, and magazine… Or is this totally wrong?
For a dedicated sniper rifle magazine size would not matter much, but then again you would probably be better off with a bolt-action rifle in any case. For a DMR a larger magazine would still be better, since you would be expected to make rapid followup shots and engage multiple targets in a short amount of time.
Good points. Had this rifle been made with a simpler bolt (if not simpler charging system) and a 15 round magazine capacity could it get onto any market and succeed?
Depend on price and marketing. Fabrique Nationale marketed successfully brand-new self-loading rifle
in world of ridiculously cheap surplus weapon from WWII.
However, I fear that Swiss designers, which apparently stick to rule:
If you ask about price, that mean you are poor would fail in international selling.
But if you want silence rifle you need sub-sonic, with smaller powder charge, which probably will not cycle action.
Using the service bolt-action rifle as the basis for a semi-automatic prototype was a popular pastime with the various ordnance bureaus of the day. The British had the “Sword Guard Pattern” experimental Enfield in WW1, and the Rieder attachment for the SMLE in WW2;
The U.S. and France (wisely, I think) stayed out of the game, and concentrated on developing “clean sheet of paper” designs, Like the Garand and M1949. (The latter actually dated to 1935.)
The Swiss had several such projects. In their case, it was made easier by their rifle being a “straight-pull”, actually a conventional turning bolt with a cam-path “sleeve” to do the turning for the rifleman.
I call these “faux” straight-pulls. This category includes the Canadian Ross, the Austrian Mannlicher Model 1887 (both of which have cam-operated turning bolt-heads like a Mauser), and all the Swiss service rifles, which have fully-rotating bolts. These are unlike the “true” straight-pull actions, such as the Lee Navy with its tilting bolt lock, or Mannlicher Model 1888 with its hinged locking flap under the bolt. Neither one has any “turning” motion whatsoever.
Generally, “true” straight-pulls are pretty “straightforward” mechanically (sorry). “Faux” straight-pulls are basically turnbolt actions with added gadgetry to do the turning bit instead of the shooter doing it with his hand on the bolt handle. Thus, they are inherently more complicated mechanically.
Complication is not a good thing in a combat weapon intended for use in a battlefield environment. (Always remember, Mother Nature is not on your side, or the enemy’s; she hates you both equally.)
Either type of “straight-pull” is easier to convert to a self-loading, gas-operated action than a basic turn-bolt rifle. Because the whole unlocking/locking motion sequence is already “built-in”, so to speak. Therefore, all the gas piston setup has to do is move the bolt (or more precisely the bolt handle) back and forth in a straight line.
BTW, the M1 Garand would be definable as a “faux” straight-pull, because the bolt turns and is operated by the cam on the operating rod. The French M1949, by comparison, would be a “true” straight-pull due to its tilting-bolt locking system. No Turning Allowed, there.
“Using the service bolt-action rifle as the basis for a semi-automatic prototype was a popular pastime with the various ordnance bureaus of the day.”
In fact converting straight-pull bolt-action repeating rifle into self-loader is simple only in theory. Major problems are:
1. Repeating rifle is designed to be operated by human, if power of powder gases it uses it is much more harsh – just notice that many automatic rifles fire ~600 rpm (cyclic, i.e. full auto and assuming infinitive magazine), no human is able to do it.
2. Where to put gas tube? Below is magazine so you need special shaped element to connect to bolt manipulator, upper would prevent usage of stripper clips (then considered default method, even for rifles with detachable magazine), side would give odd center-of-gravity point.
“The U.S. and France (wisely, I think) stayed out of the game”
In France, many parts for obsolete Lebel rifle was used for production of RSC Modèle 1917:
It used furniture parts, barrel and tubular magazine (as gas tube) from Lebel.
BTW: Any gas-operated self-loading rifle might be converted to straight-pull bolt-action repeater, simply by welding gas hole, French Army did it, as mentioned in above link, however I’m not sure why?
I said it was a “popular pastime” with the BuOrds, I never said it was simple, practical, or a particularly good idea.
As for why the French converted the St.Etienne self-loaders to straight-pull bolt actions, they were never particularly reliable as self-loaders, less because of their actions than the fact that the 8 x 50R Lebel cartridge isn’t really well-suited to any sort of self-loading action. But then the French really had no good “domestic” choices, as basically all their military rifle rounds of the era were based on the Lebel case. (Yes, even the 6.5 x 50R Daudeteau.)
After the war, to avoid admitting that the St. Etienne rifle just didn’t work worth anything, they pulled the old trick of sending the inventory to arm their colonial outposts and the Legion Etrangere’. This was the standard French Army dodge to get rid of a weapon that sucked- when they declared that a weapon was “best suited to the tropical service”, the “tropical service” knew that really meant, “BOHICA”. (The same held true for any weapon declared “ideal for fortress use”, anywhere.)
But before shipping them off to Devil’s Island and etc. (literally- the guard force there got a full set), they welded the gas ports shut to make them (overly heavy) straight-pull bolt-actions. To better disguise just how unreliable they were.
Today, an un-modified M1917 or M1918 is uncommon enough to be worth quite q bit more on the collector market. And just because one shows up with the gas port welded shut does not mean it is a “dewat”- they were in fact issued that way after 1919.
“But then the French really had no good “domestic” choices, as basically all their military rifle rounds of the era were based on the Lebel case. (Yes, even the 6.5 x 50R Daudeteau.)”
Daudeteau cartridge if you mean this cartridge:
was actually semi-rimmed cartridge, can you prove that it is child of 8x50R Lebel? Dimensions suggest that it is independent cartridge.
France had better-suited rifle cartridge for self-loading rifle then – 7×57 Meunier, however they decided to use 8x50R Lebel to no complicate supply.
6.5 Daudeteau on the left, 8 Lebel on the right.
Technically, it’s the 6.5 x 53.5 SR Daudeteau, so yes, I stand corrected. But it was in fact based on the 8 x 50R Lebel case, as this makes pretty obvious.
Even though the SR case head would be better for any feed system other than a tube, the dimensions and taper of the case probably would not lend themselves to reliable feeding in a self-loader much more than the Lebel did.
It’s interesting to note that the only really reliably-feeding MGs using the 8 x 50R were the Hotchkiss (strip feed) and the Lewis (pan magazine).
I don’t believe that any belt-feed weapon was ever proven to be a reliable feeder with the 8 x 50R. Not even the Vickers, which fed 0.303in extremely reliably.
It just wasn’t a very good cartridge design for anything except the rifle it was originally designed for. Which was rapidly rendered obsolescent by advances in the technology. (Plus, people learning by trial and error what did and didn’t work.)
“6.5 Daudeteau on the left, 8 Lebel on the right.”
This is not 8x50R Lebel, Lebel cartridge has not extractor groove and has different shape:
Very strange choice tilting bolt. Original K31 rifle with sliding bolt was very close to a gas operated rotating head rifle.
Thanks Ian. Again– excellent and informative presentation!
Any idea why it was not adopted by the Swiss?
What was its weight?
Guess you didn’t have the opportunity of running a few rounds through it.
Also, guess this gun was not an auction gun so it is not for sale.
“What was its weight?”
Data from A.B.Zhuk:
Overall length: 1110 mm
Barrel length: 590 mm
Weight: 4,5 kg
A ten pound rifle seems a bit heavy to carry all day…
In most cases self-loading rifle is heavier than same-cartridge repeater.
4,5 kg is quite heavy from modern point-of-view, but should be acceptable in 1940s (for example Egyptian HAKIM rifle is 4,4 kg)
Most versions of the AR-15 series in 5.56 x 45mm weigh about 9.5 lbs with a full magazine underneath. Only the very early AR-15s used by the U.S. Air Force for base security back in the early 1960s ever made the “official” weight of 6.5 lbs empty.
And starting with the U.S. Army’s original M16 version, the weight went up as the components were beefed up to handle things like sustained fire, being thrown in the back of a truck, etc.
Most combat rifles of whatever caliber weigh between 9 and 11 pounds (4 and 5 kg). Generally, .30 caliber class ones tend toward the upper end of the scale.
Ones “re-engineered” as squad automatic weapons or “Designated Marksman” rifles can easily break 15 pounds (6.8 kg) and some make a good go at 20 pounds (9.1 kg).
As the old saying goes, “Power, Reliability, Low Mass. Choose Any Two.”
The Finnish Sniper Rifle M85 (TKIV 85, a.k.a. TAK 85) in 7.62×53R weighs 7 kg (15.4 lbs) empty and without an optical sight, although the weight does include the bipod. Perhaps not surprisingly, the weight is one of the biggest criticism of the weapon. It weighs the same without the scope as the Finnish Army Sako TRG-42 (TKIV 2000) in .338 Lapua Magnum with the Zeiss 3-12×56 Diavari scope.
For those who may not know: the M85 was/is probably the last development of the Mosin-Nagant for military use anywhere. It’s a very accurate rifle within the practical range of the 7.62×53R cartridge (about 700-800 meters), but the weight and ergonomics seem like it was designed in the 1930s and not in the 1980s….
Most mind-boggling question for me is: why they craft it for 7.92×57? It suggest that it was export weapon, but for who? Who used 7.92×57 as default rifle cartridge and might be interested in buying brand new self-loading rifle in 1946?
Maybe South America? I believe Mausers were making inroads there since break of Centuries.
Btw, I also own Zhuk’s books; both on rifles and pistols.
But they used either 7×57 Spanish or 7.65 Argentine so far I know, not 7.92×57.
I suspect that this rifle might be developed for Portugal which switched from 6.5×58 to 7.92×57 in late 1930s. For some reason (too expensive? fail to pass field trials?) it was not adopted, so SIG reworked it for 7.5×55 and try to sell it to Swiss Army but without success.
Hmmm. Perhaps Portugal, but I don’t think. The Portuguese military had shown some interest in acquiring self-loading rifles before the switch from 6.5×58 (and .303) to 7.92×57 (from the late 20s onwards), but after the standardisation of 1937, with the adoption of the m/937 and the local conversion of Mauser-Vergueiros m/904 as the m/904-39 they didn’t seem to bother.
Most likely because the 7.9 x 57 case was the basis for most of the others (it was descended from the 7.65 x 53, itself).
All of the Mauser rounds have approximately the same case-head/rim specs (.469-.470″ base, .473-.474″ rim), except the one-off 6.5 x 55mm Swedish version. The .30-06 shares these specs. So a rifle designed around the 7.9 x 57 could be chambered for just about any round within its “envelope” that the customer wanted, without changing the bolt head, extractor, etc. The cartridge OAL would be the deciding factor, i.e. would it fit in the magazine front-to-back?
By comparison, the 7.5 x 55 Swiss Schmidt-Rubin has a .494″ base and a .496″ rim. The majority of rounds with a base diameter that size are rimmed ones, like the 8 x 58R Danish Krag or the Japanese 8 x 53R Murata. About the only rimless round with a similar head and rim is the Italian 8 x 59 Breda heavy MG round. Which nobody else ever used.
In short, the 7.5 x 55 S-R isn’t a very good choice for a rifle that needs to be adaptable to the most common military rounds in circulation. It’s the wrong size.
BTW, in spite of its “7.5mm” caliber designation, the Schmidt-Rubin uses 0.308″ bullets, just like everybody else’s .30 calibers and 7.62mms.
7.62×54R actually uses .312″ (7.92mm) bullets (some sources say .311″, but the difference is hardly critical). Finnish 7.62×53R uses .310″ or .309″ bullets.
The .311 (.303) is inherited from the favourable results of Rubin’s experiments with small bores.
Britain was simillarly impressed by Rubin’s results and was initially very impressed by Rubin’s bolt action too.
During trials it emerged that the Lee action was the more durable, so The Brits adopted a lee action and a Rubin inspired round of .303/.311″
the 7.9 mm Patrone 88 was developed by the military (Gewehr-Prüfungskommission and the military institutions at Spandau) in great secrecy, as was the rifle for it, Gewehr 88. At the same time Mauser/DWM created their 7.65 mm cartridge and a rifle for it. There is no evidence I know of which would hint at Patrone 88 being derived from the 7.65 mm Mauser.
Gentlemen, as a finn I have wondered a long time why only us finns call this Russian 54R for 53R?
Stupid question I know, but I do not know!
Finnish cartridge has slightly smaller bullet diameter (7,85 mm vs 7,92mm)
In practical terms this means that you should probably avoid shooting a steady diet of Russian 7.62x54R military ammo with bi-metal a.k.a. steel jacketed magnetic bullets with your Finnish Mosin-Nagant. With commercial copper jacketed bullets there should be no problems whatsoever, and I don’t think there are any documented cases of a Finnish Mosin failing in any way with the Russian bi-metal jacketed bullets. The diameter difference is too small and the steel jacket is soft steel. It will, however, wear the barrel down somewhat more rapidly, since even soft steel is still much harder than copper.
There’s a lot more to barrel wear than jacket hardness.
Ignoring for the present, the question of whether the barrel is taking full auto fire, in which case significant softening of some steels occurs
The friction and abrasive properties of the jacket material are not dependant on hardness alone.
sure a higher yeild point for a jacket material could be expected to result in higher normal stress at the corners of the rifling lands, and possibly less sealing on the sides and top of the land
but only if engraving force is the largest force acting. I suspect (I havent done the calcs for steel jackets) that the radial pressure from the core material plastically deforming under accelleration, may be a greater source of pressure. My reason for thinking that, is the lack of gas leakage past the jackets, whether steel or copper based.
Now to the slippery subject of tribology, and the possible presence of hard inclusions.
is the steel with or without copper plating, actually going to wear the bore more than gliding metal or cupro nickel? and will mild steel on hard steel slide easier than the other jacket materials?
Highest quality watch and instrument makers lathes used to have hardened steel plain bearings. the used to have part – is only because of expense of manufacture, not because of lack of performance.
In a lather or a mill, machining pure copper is a bugger for eating tools! IMO it’s far worse than even chewy mild steels