The Valmet M71 was introduced as a commercial export rifle in 1971, and was the first AK available on the commercial market in the United States and Europe. It was offered in both .223 and 7.62x39mm calibers, because the 7.62x39mm cartridge was rare and expensive at the time outside of Finland and the Soviet bloc. As a result, the majority of sales were for .223 rifles. The vast majority were sold as semiautomatic rifles, but this one has been legally converted into a fully automatic machine gun, per the NFA.
To make the M71 appear more “AK-like”, Valmet opted to revert to the Soviet style of sights, with a notch on the front of the receiver and a post mounted at the muzzle (as opposed to the Valmet military pattern, which used an aperture mounted at the rear of the top cover and a front post on the gas block). They also appear to have maintained the Soviet gas port size, as the rifle recoils more than one might expect for its caliber. This was done intentionally, to ensure that it would continue to function reliably in very cold weather, when ambient temperature causes chamber pressure to be reduced.
Thanks to slowed-down video it is possible to observe elastic deformation of entire weapon even in this ‘mickey-mouse’ caliber. When comes to ‘over-gassed’ system’s role in it, it is a bit of question. First (larger) spike comes from cartridge impulse while bolt is still locked, not action to frame impact.
In any case, both Russian (AK47 an AK74) guns employ piston diameter of 14mm, way over what it needs to be. Western guns pistons feeding 5.56 shot are in range of 10-12mm. Lately, on AK12 and AK15 iterations they compensate this problem with gas adjustment.
“AK47 an AK74”
What I could say now? Only: http://www.nooooooooooooooo.com/
АК (alternatively 56-А-212 would be acceptable) not АК-47, unless you mean particular prototypes of АК: https://kalashnikov.media/media/photogallery/4516588
” Western guns pistons feeding 5.56 shot are in range of 10-12mm.”
What about vz. 58: https://modernfirearms.net/en/assault-rifles/czech-republic-assault-rifles/sa-vz-58-eng/ ?
I do not intent to search information on vz.58 piston size, but in my visual recollection it was no mere than 12mm. The gas chamber was not easy to clean since it was blind; much like AK. But both the chamber and piston were chrome plated.
By far the best features on vz.58 was magazine and visibility of chamber. I never seen a stoppage (2nd year as weapon tech); its magazine was brilliant – ight and strong. The worst part was ejection; way up so everyone knew where you are hiding.
“First (larger) spike comes from cartridge impulse while bolt is still locked, not action to frame impact.”
Regarding Kalashnikov system dynamics/kinematics (choose one, I have no enough knowledge to decide which word is proper) that pdf might be interesting:
it is centered around Bulkin avtomat for 7,62 model 1943 cartridge – one of serious competitors of Kalashnikov, nonetheless contain data on other competitors on well.
I will just explain illustrations and chart.
upper: Kalashnikov experimental avtomat, tested in August 1947
lower: Bulkin experimental avtomat, tested in August 1947
top right: M.T.Kalashnikov
bottom right: A.A.Bulkin
top left: bolt of final iteration of ТКБ-415 by Bulkin, it was same as in tested Bulkin avtomat
top right: bolt of АКМ, not much different from prototypes
bottom left: drawing explaining Kalashnikov (top) and Bulkin (bottom) bolts
Chart (велограмм): velocity vs movement, left: Kalashnikov, right: Bulkin, blue: normal conditions, orange: dry* condition (no grease)
[This chart is here interesting for us]
Column 4 is mass of all moving parts, kg
Column 8 is velocity [of moving parts] at end position [action fully opened]
Column 10 is travel of moving parts [between action fully closed and action fully opened]
Last row is PPSh sub-machine gun, possibly added as sample (it is not relevant, as it is blow-back operated, so in some respect it has values denoted by – meaning DOES NOT APPLY)
Second from bottom is “MP44”, weapon more commonly known under StG designation.
All others are entrants to competition by Soviet designers.
Bulkin’s ТКБ-415, final iteration
ТКБ-392 by Bulkin, self-loading rifle for 7,62 mm model 1943 cartridge
How it ended:
Kalashnikov better than Bulkin in regard of reliability, especially with dry elements.
* in Soviet “dry” test elements were washed in gasoline, between firing of weapon
is: “(…)Column 8 is velocity [of moving parts] at end position [action fully opened]
Column 10 is travel of moving parts [between action fully closed and action fully opened](…)”
should be: “(…)Column 8 is velocity [of moving parts] at end position [action fully opened], m/s
Column 10 is travel of moving parts [between action fully closed and action fully opened], mm(…)”
As side note, very little about Bulkin, Russian Wikipedia has short query:
it shows image, which is currently only known photo of A.A.Bulkin.
It is not known where or when he was born or died, in fact more data regarding his avtomat is available than himself.
Following development which he influenced are known to exist:
mounted machine gun and automatic rifle, together with I.I.Rakov
light machine gun, own work, tested in 1943
ТКБ-392, self-loading rifle (7,62 mm model 1943 cartridge), own work – this artifact is actually in possession of ЦКИБ СОО, it is not mentioned in documents regarding development of such weapons [which ultimately leaded to SKS]
fast-firing aviation autocannons together with N.M.Afanasyev and M.E.Berezin in ЦКБ 14 (now it is КБП Тула)
This query has link to other interesting query:
Hypotheses on creation of Kalashnikov Avtomat
Summing up, it described following hyphotheses
1. Kalashnikov as protégé – someone powerful acted so Kalashnikov win
2. Copying of Bulkin avtomat – it is fact, that some solution from Bulkin were copied, however Kalashnikov avtomat is not direct copy, rather synthesis
3. Simonov is author
4. Copying of StG-44
5. Copying of ZK-420* – hammer-trigger-groups are quite similar for AK and ZK-420
6. Wasserman’s hypothesis – Kalashnikov did not develop no new solution, but rather synthesized known solution, so Kalashnikov did not receive over-all patent for his avtomat. This hypothesis that Kalashnikov was constructor, but not developer. Workers of НИПСМВО also helped Kalashnikov, which was prohibited, as this make danger they will prefer his design. Finally Kalashnikov win, but trials were, so far I know, not rigged. Fact that such action were prohibited might explain why they wanted to assign their own works to Kalashnikov
ZK-420 is rifle developed from self-loading ZH-29 by Václav Holek
НИПСМВО is Scientific-Research Proving ground [of] Fire-arms and adjective(Mortar) Weaponry, in 1940s this entity was responsible for examining weapons patterns before introduction to Soviet forces service
Thanks for information on Bulkin’s avtomat. In my visual observation, better design than Kalashnikov. I mean namely bolt design and its rotation control. Looks more robust; dirt reliefs are smart too. Also I like his self-loading rifle. He must have ended up unsatisfied.
But basically they are very similar as far as operating concept goes. You cannot go wrong with long stroke, gas operated system. Very positive opening and extraction when pressure in barrel is mostly gone; energy stored in piston/ carried is plentiful.
As a matter of fact – it occurred to me: Bulkin’s way of bolt control is very much the way Slovak (GP?) rotary barrel pistol operates. We know now who was first.
The problem in cold weather may have had more to do with the lubrication getting thick. Oil and grease viscosity is a problem with any lubricated machinery in cold weather.
Weapon of choice scenario:
Location: a very cold, dark, and smelly tunnel of the West Königsberg sewers
Ugh! Remind me never to accept missions for pest extermination with the Police ever again! We just killed a 4 foot 11 inch tall (not including tail) humongous mutant rat moments earlier, and according to intelligence, there are more rats like it all over the place but they’re bigger!! And I’m certain city hall doesn’t want to wait to hire the next exterminator to come in order to deal with the rat problems, seeing as the first guy was eaten alive by those rats. To make matters even worse, it seems that some mad scientist intentionally created the monster rats just to get revenge on the city for refusing to fund his unethical genetic projects. If I’m not mistaken, there’s more than just rats down here in these sewers. I thought I saw a two-headed crocodile in the water five minutes ago. Who knows what else we’re going to kill next…
At least 5000 mutated giant rats, one of which is the size of a Mack NO truck (!!)
5 mutated crocodiles (!!)
60 bandits, all armed with stolen AK-74’s
1 mad scientist with vials of dangerous chemicals and a “Wunderwaffe DG-2”
Objectives: Surviving the onslaught of mutant rats, elimination of the bandits, and either killing or capturing the mad scientist…
1. MP-443 Grach
2. Colt Python
3. Desert Eagle in .357 Magnum
4. Stevens 520-30 with sword bayonet
5. Beretta MAB-38A
6. M30 Luftwaffe Drilling
7. Valmet M71
8. FN Model D
9. РОКС-3 flamethrower
10. pocket canisters of chlorine gas
11. Or per the usual, screw the budget and add your favorite toys to this list!
12. Screw this, get the Davy Crocket!!
This is all I can do for you now.
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Knowing the size of rats, I wonder if standard equipment is enough.
Let’s use gas to prepare the ground (something like burning all oxygen, or using Sarin. I’m a bit reluctant to use VX to limit ecological damages outside the area)
Wait enough for effects.
Then we send a team with proper equipment, ready to confront the lucky ones who could find a breathable shelter.
“At least 5000 mutated giant rats, one of which is the size of a Mack NO truck (!!)
5 mutated crocodiles (!!)”
Standard handguns are too weak for that.
“dark, and smelly tunnel of the West Königsberg sewers”
This complicate much situation. No classic recoilless rifles, as you could fry yourself in tiny space. Armbrust http://www.military-today.com/firearms/armbrust.htm might be solution there, as it arrest powder gases inside.
The Armbrust also has the unprecedented feature of a venturi and muzzle that seal the instant the rocket leaves the tube, making it smokeless, flashless, and no louder than a pistol shot when fired. The countermass eliminates fan of debris created by the backblast, and also allows the Armbrust to be fired from inside confined spaces. The danger area behind the Armbrust is only a few meters in area, so the operator can fire it from a confined space, such as a pillbox or a small room, and it is safe to fire the weapon even if there is a tall vertical obstacle such as a wall directly behind the operator — though at least 0.8 m of relief is still required to safely fire the weapon
“Or per the usual, screw the budget and add your favorite toys to this list!”
6П62 http://guns.wikia.com/wiki/6P62 should be enough for most rats, as it use 12.7×108 cartridge, is also quite short so could be used in confined areas.
“I wonder if standard equipment is enough.”
Alternatively, I would suggest enforcing said rats to abandon sewers, thus allowing fighting in open area. Irritant chemical agent could be used, however this need knowledge which one rats fear (will escape from area contaminated)
Flamethrower in tiny space? Very bad idea. Firstly there is danger that burning will consume oxygenium and as you know humans do not remain alive for long without supply oxygenium. Secondly in dark places it might make firer (temporarily) blind. Thirdly flames from flamethrower can also “bounce” from obstacle.
Oops! Maybe I should have suggested dropping grenades down the manhole instead. Or, wait near a sewer exit with the flamethrower as opposed to being in the sewer with it. Have a friend flood the system with irritant gas, burn rats as they exit choking. That way you toast the intended victims and not yourself. I suppose only the PIAT looks better for use in cramped spaces…
Ian, I don’t suppose you have the ability to measure the gas piston length, would you? We (KNS) we got the data to produce gas pistons for the Valmet M76 (and 77, too, I think) and it’d be great to be able to cover the full gamut of Valmet products. Especially since it appears there’s some significant overgassing. That jostle at the end of BCG reciprocation is exactly what an adjustable gas piston can address. Possibly even the AK barrel wiggle-dance, too.
I have almost the exact gun in the video, F/A and all. It does kick a bit more than an AR, but it’s still perfectly simple to control. The sights are a bit thick for anything beyond CQB, but they work. And that delicious Finn quality is there. Even my Tula AK74 rattled around, but the Valmet is much tighter and smoother.
On a side note, Galil mags CAN be safely modified to work in an M71. I have a dozen modified Galil mags that run just fine, both in semi and full. And that’s great news for those of us who don’t want to pay $100 per mag.
Ian, I own a Valmet M71 non-factory wooden buttstock, pistol grip, and handguards set I can find no definitive information on. Got them out of a parts kit. Have many pictures if you would be interested in checking them out and maybe figuring out where they came from.