Russian gun caliber question

[General Bolt]

Years ago I heard, that the reason the Russians made a 76mm gun, was in the event any russian ammo was captured it wouldn't fit in to a 75mm gun. However, it thr Russians captured some 75mm German ammo it could fit in a 76 gun.

Same reason for the 82mm mortar vice the 81mm.

Is this true? or was it a sloppy measurement on a copyright violation?

[Michael Emrys]

The 76mm was a standard caliber in the Russian armory going back to Czarist times.

Regarding the 82mm vs. 81mm, I've heard a similar story, but I have also heard it rebutted. I frankly don't really know what the truth of it is. But consider the rumor can cut both ways. The Germans could also fire their ammo through captured Soviet tubes.

Michael

[slysniper]

I remember reading the same facts, but where I came across it was in military manuals, stating

that Russia had used this concept for design and that it still is used as a basic design concept, to calibrate larger than there enemies.

[Krautman]

I read that one reason german troops liked the 81mm GrW, besides its durability + simple and sturdy design, was that they could use "most captured ammunition" with it ("most captured" grenades should, as land warfare was mostly fought in the ussr, include russian 82mm?). I personally doubt that a 82mm grenade would fit in a 81mm tube, but maybe they could modify the grenades anyhow.

[Mad Russian]

I was told this in the Army as well. It was in some manuals. If you look the Soviet gun sizes from small arms all the way through their largest weapons are just a little larger. This could have been a very smart design concept on their part. I find it hard to believe that it would be completely by accident that they are all just a little bigger.

Good Hunting.

[Foreigner]

Actually, caliber is not the only criterion for 'fitting' an opponent's ammunition to your own guns. Especially for self-contained cartridges, length and cartridge shape can be quite different between similar rounds, not to mention the possibility of drastic differences in propellant loads and rated pressures.

But there are at least two possible reasons for the general tendency of Soviet/Russian weapons systems to be of slightly bigger size.

First, design and manufacture tolerances need not be that strict, which translates into weapons that, while not so 'sophisticated' or finely made, are cheaper to produce and maintain, and are generally more reliable under adverse conditions.

Second, if you are to adapt a captured round, it is always easier to 'pad' a small round than to 'cram' a bigger round into a smaller chamber - not to mention safer. Imagine filing away extra metal from a HE shell...

[John D Salt]

Originally posted by Foreigner:

Actually, caliber is not the only criterion for 'fitting' an opponent's ammunition to your own guns. Especially for self-contained cartridges, length and cartridge shape can be quite different between similar rounds, not to mention the possibility of drastic differences in propellant loads and rated pressures.

Indeed so. Not all Soviet 76mm pieces could fire all Soviet 76mm rounds.

Originally posted by Foreigner:

First, design and manufacture tolerances need not be that strict, which translates into weapons that, while not so 'sophisticated' or finely made, are cheaper to produce and maintain, and are generally more reliable under adverse conditions.

This seems unlikely to me. Don't forget two things:

1. The calibre used in a weapon designation is often only a nominal calibre. I doubt that there was typically any difference between weapons designated 75mm and 76.2mm.

Which bullet do you think is wider, a British .303 or a Russian 7.62mm?

2. Barrel wear in rifled weapons makes a considerable difference to the actual calibre during a weapon's service life, and there is a fair amount of "slop" that can be taken up by the driving band (which provides obturation as well as engaging the rifling). The condemning limit of wear for the 17-pdr, for example, was one-tenth of an inch, more than twice the difference bnetween 75mm and 76.2mm.

Of course the second point doesn't necessarily apply to smoothbore mortars, but I wonder if the actual calibre of an 82mm tube is any different from that of an 81mm (or 8cm or 3-inch).

All the best,

John.

[Leopard_2]

Originally posted by Foreigner:

Actually, caliber is not the only criterion for 'fitting' an opponent's ammunition to your own guns. Especially for self-contained cartridges, length and cartridge shape can be quite different between similar rounds...

This is rifles, not guns, but I quite vividly remember my army times, where I was drilled to understand that the "calibre" of my G3 battle rifle is not 7.62, but 7.62x51mm (as opposed to, for example, the 7.62x39mm of the AK-47), and the pistol / MP calibre is not 9mm, but 9x19mm.

[Bone_Vulture]

I'm no gunsmith - I've only had experience with the Finnish military assault rifle RK-62 (the best Kalashnikov variant in the world, some say). But I do think that the most important factor is the size and shape of the cartridge; it can prevent the ammunition from being loaded into the chamber altogether.

I'd assume firing slightly over-caliber artillery ammunition is possible in some cases, but will likely result in increased wear of the barrel rifling, the least.

[flamingknives]

Most barrel wear, AIUI, comes not from frictional wear from the driving band, but from chemical erosion by the propellant gases. Low power rounds can 'copper' a bore with residual material from the driving band, while higer power ones can strip it off (only noticable on howitzers)

[Mejsel]

I couldnt imagine using non-issue munitions in the ways suggested in this thread. No offence but it does not add. My practical experience firing mortars is not extensive but it is worth two cents...

The difference caused by 1-1.62mm bore diameter makes for a large portion of randomness. At normal bussiness-range for medium mortars one can expect to approach and exceed the impact pattern of Target Wide in game terms. Thus making it dangerous for friendlies as well.

This is not comparable with the normal wear of a barrel firing issued munitions were the "decline" is more graceful. As such it can be accounted for and compensated against.

As for the use of captured shells of any kind... well its war. Explosives always come in handy.

[JasonC]

These differences mostly reflect old imperial measurements, and conventions and practices adopted when converting them to the metric system.

76mm guns are simply 3 inch guns. Designed that way, with rulers with inches on them, and handed down as exact designs and machinery to people later using metric measurements. (88mm guns are 3.5 inches. So are 25 pdrs).

7.5 cm guns, on the other hand, were designed by people with rulers with centimeters on them. Notice, the Germans did not even call them 75mm, the convention of using mm as a universal measure comes later, to put everyone's conventions together.

81mm mortars are 3.2 inch mortars, and British 3 inch mortars are the same caliber. They were designed that way, imperial measurements. The extra tenths were to ensure the rounds easily got down the tubes, since they were muzzle-loading. The Germans called them 8 cm mortars not 81mm. As a fact, the physical dimension was 81.4mm - because that is 3.2 inches imperial measure, and everybody was copying the same physical specimens to make their own versions.

Russian 82mm are the same dimensions as German 8 cm mortars. They just rounded the 0.4mm left over up instead of down. Mostly a convention. Probably did not want someone making a barrel to the new spec that was too small for the rounds.

The idea that ammo use considerations was involved is a later legend made up to explain the fiddly differences. I've heard similar stories told about 106mm recoilless rifles, which are in fact 105mm in diameter, and only called 106mm to make sure the ordnance types back in supply don't send the wrong round. There are similar uses of designations like "77mm".

The Germans used captured Russian 76mm guns, and 122mm, and 152mm, and French 75mm and 155mm. Some they used with captured ammo as is. They also captured plants that made ammo, and later ran their own plants making French or Russian ammo, they had so many captured pieces to feed. It is not that hard to reproduce enemy ammo styles if you actually want it.

For others, they wanted to use a Russian gun but German ammunition, because their ammo was better and the difference mattered. An example is the Russian long 76mm (76L51), used for AT guns and Marders. They didn't use the Russian ammunition, and they didn't need to fiddle with the barrels. But they did rechamber guns to take their own ammunition, with a longer cartridge and more powder. That means replacing the breech block area and the like, and is definitely a factory not a field process.

[Zalgiris 1410]

Just my 2 cents, IIRC the Russian Imperial system was definately responsible for the 7.62mm rifle & later MG rounds because it was a tenth of 76.2mm and referred to as a grain I think, and hence by extension the 76.2mm guns.

[rum]

Originally posted by General Colt:

Years ago I heard, that the reason the Russians made a 76mm gun, was in the event any russian ammo was captured it wouldn't fit in to a 75mm gun.

Its just a BS.

The only and the main reason that USSR designed 76.2mm cannons is the large stock of 76.2mm cannon from the World War I.

[John Kettler]

JasonC,

Your anecdote about the 106 RR (about which I never knew) is neatly parallelled

and reinforced by Suvorov's explanation in INSIDE THE SOVIET ARMY, where he states that the West's general failure to distinguish different weapons of the same caliber by changing the listed bore size is a source of bafflement to the Russians.

Their approach is based on understanding the critical need to keep things simple, especially amid the chaos of war for millions of reservists suddenly called to the colors after years away from the army. A telling example he gives is of

how Stalin's eagerly awaited firing trials for the Katyusha had to be postponed for weeks when, instead of rockets, someone mistakenly delivered 130mm cannon ammunition to the artillery proving grounds. Heads could literally have rolled over this debacle, but Stalin simply decreed that henceforth the rockets would be called 132mm. According to Suvorov, the rocket for the BM-13 eventually grew to be 132mm in diameter.

Regards,

John Kettler

[rum]

Originally posted by rum:The only and the main reason that USSR designed 76.2mm cannons is the large stock of 76.2mm cannon from the World War I. [/QB]

Duh...

Of cause i meant "large stock of 76.2mm cannons ammo"

[Zalgiris 1410]

I believe the discussion rum is why the Russians chose calibers of 7.62/76.2/82/122mm etc, in the first place, and what the implications are of having done so!