# 82mm mortar va. 81mm mortar **URL:** \ **Category:** Factual Questions\ **Created:** [October 9, 2017, 4:12am UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356 "2017-10-09T04:12:29Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [October 9, 2017, 4:12am UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/1 "2017-10-09T04:12:29Z")
Or a .51 caliber machine gun vs. a .50 cal. The idea was that the commies could load our ammunition into their weapons On the other hand, their rounds were too big to fit through our barrels. Did this ever happen, to the point where it influenced the outcome of a battle? ---
**Author:** ![Toledo\_Jim](https://avatars.discourse-cdn.com/v4/letter/t/34f0e0/32.png) [@Toledo\_Jim](https://boards.straightdope.com/u/Toledo_Jim)\ **Post date:** [October 9, 2017, 4:28am UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/2 "2017-10-09T04:28:14Z")
Well, it depends. With the mortar, clearances are a bit loose, length of the round is less important, etc. unless the 81 and the 82 have different firing mechanisms they likely would be nearly interchangeable. The machine gun issue is quite a bit different. What we might call .51 cal is actually 13mm. This is a common metric caliber. Our .50 caliber dates back quite a while, like nearly a century (was designed by Moses Browning). But the way the two are chambered, the length of the round, the firing (rimfire/centerfire), the detailed shape of the round can all be different. No, you cannot just feed .50cal rounds into the 13mm gun. ---
**Author:** ![Asuka](https://avatars.discourse-cdn.com/v4/letter/a/dec6dc/32.png) [@Asuka](https://boards.straightdope.com/u/Asuka)\ **Post date:** [October 9, 2017, 5:24am UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/3 "2017-10-09T05:24:30Z")
Looking at Wikipedia, it looks like the 82mm and 81mm mortar difference dates back to before the Cold War but does seem like it was intentional. The first 82mm Soviet mortar was the 82-PM-36 which debuted in 1936, and was based on the French Brandt mle 27/31 81mm mortar which itself influences a lot of other mortars fielded by countries like the United States, Germany, and Japan. Uniquely though every other mortar was a similar 81mm design while the Soviets were the only ones to convert the design to 82mm. And according to the Wiki page _The M-36 could fire German 81 mm ammunition but range and accuracy suffered._ ---
**Author:** ![Dissonance](https://avatars.discourse-cdn.com/v4/letter/d/85f322/32.png) [@Dissonance](https://boards.straightdope.com/u/Dissonance)\ **Post date:** [October 9, 2017, 2:38pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/4 "2017-10-09T14:38:27Z")
> [@chacoguy](#): > > Or a .51 caliber machine gun vs. a .50 cal. What .51 caliber machine gun? Soviet heavy machine guns were [14.5x114mm (.57 cal)](https://en.wikipedia.org/wiki/14.5%C3%97114mm). Good luck trying to fire a 12.7x99mm cartridge with it. > [@chacoguy](#): > > The idea was that the commies could load our ammunition into their weapons > > On the other hand, their rounds were too big to fit through our barrels. No it wasn’t. Standard Soviet artillery calibers were 122mm and 152mm to NATOs 105mm and 155mm. Soviet tank guns were 100mm, 115mm and 125mm. NATOs were 105mm and 120mm. The 7.62x51mm NATO cartridge is not interchangeable with either the 7.62x39mm cartridge used by the AK-47 nor the 7.62x54mm which was originally developed for the Mosin-Nagant rifle. > [@chacoguy](#): > > Did this ever happen, to the point where it influenced the outcome of a battle? It didn’t happen because it wasn’t designed to, but if you’ve captured large stockpiles of the enemies ammunition you’ve likely captured large numbers of their weapons as well. You’re more likely to use their captured weapons and find or create a source for more ammunition for these weapons to use. Look at Germany during WWII (the Marder series of self propelled anti-tank guns used captured Soviet 76.2mm guns for example) or Israel during the Arab-Israeli wars (Israel used large numbers of captured BTR-152, T-55 and T-62, often modified for their own use as with the Ti-67 and Ti-67s which replaced the 100mm with a 105mm gun, the Soviet engine with a US diesel engine, the Soviet 12.7mm DSHk with a US M2 12.7mm, etc). Oh, and the DSHk (12.7x108mm) is presumably what you are calling a .51 caliber. Ammunition for the DSHk and the M2 (12.7x99mm) aren’t interchangeable [either](https://en.wikipedia.org/wiki/12.7%C3%97108mm#Incorrect_interchangeability_claims). > [@](#): > > It is often claimed that the US .50 BMG (12.7×99mm NATO) cartridge can be fired in Soviet/Russian 12.7×108mm machine guns. The 12.7×108mm was even called a “.51-caliber.” This often claimed interchangeability is an assumption made from[dubious – discuss] the 12.7×108mm being listed as “.511-caliber” in US intelligence publications during the Vietnam War. The bullets used for both cartridges are ~.51 inches in diameter. .50 caliber, 1/2 of an inch, is the diameter of the hole bored down the barrel of the gun first. Then rifling is cut all around the bored hole to a depth of .005". Thus, .500 + .005 + .005 = .510." Upon firing the bullet engages the rifling, and .005" grooves are pressed into the surface of the bullet to impart spin to stabilize the bullet. Despite the similar bullet diameters, the dimensional differences between the two cartridges would prevent either being correctly chambered in a firearm designed for the other. ---
**Author:** ![Corry\_El](https://avatars.discourse-cdn.com/v4/letter/c/ecae2f/32.png) [@Corry\_El](https://boards.straightdope.com/u/Corry_El)\ **Post date:** [October 9, 2017, 3:54pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/5 "2017-10-09T15:54:33Z")
> [@Toledo\_Jim](#): > > The machine gun issue is quite a bit different. What we might call .51 cal is actually 13mm. This is a common metric caliber. To further clarify, the Soviet/Russian caliber comparable to the US .50 is 12.7mm and it’s usually called that. As mentioned above the _bullets_ of .50 BMG (Browning Machine Gun) 12.7_99 and Russian 12.7mm or 12.7_108 are almost identical in diameter, the .50 BMG bullet is very slightly larger. But the Russian round’s cartridge case is significantly larger and it’s not practical for weapons of that power to run a smaller cartridge case through a bigger chamber. The US military appellation ‘.51 caliber’ for the Russian DShk 12.7mm machine gun might have originated as a simple way to note it didn’t fire the same ammo as the .50 Browning without getting into the actual explanation of the difference. 13mm usually refers to the 13.2mm round used by the French, Japanese and other countries in WWII era. The case of that round (13.2\*99 version) is similar in size to that of the .50 BMG but the bullet has a greater diameter. Versions of the Browning MG chambered for 13.2mm were used by both France and Japan alongside gas operated Hotchkiss types, the round generally being referred to as 13.2mm Hotchkiss. But again guns chambered for one couldn’t practically fire the other. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [October 9, 2017, 4:35pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/6 "2017-10-09T16:35:52Z")
> [@Corry\_El](#): > > The US military appellation ‘.51 caliber’ for the Russian DShk 12.7mm machine gun might have originated as a simple way to note it didn’t fire the same ammo as the .50 Browning without getting into the actual explanation of the difference. The US did something like that with a tank gun, too, calling one 76mm instad of 3-inch to make it clear that the ammo was different. > **[76 mm gun M1 | Design and development](https://en.wikipedia.org/wiki/76_mm_gun_M1#Design_and_development)** > > Before the United States had battle experience against heavily armored German tanks, the development of a weapon superior to the 75 mm gun was anticipated. The original Ordnance Department specifications of 11 September 1941 for the M4 tank allowed for the mounting of numerous weapons including the 3 inch gun. The first specimens of the weapon that was to become the 76 mm Gun M1 were being evaluated in August 1942 while the U.S. did not enter the ground war in the European-African-Middle Easte Th... “It fired the same projectiles as the 3-inch (76 mm) M7 gun mounted on the 3in Gun Motor Carriage M10 tank destroyer and towed 3-inch Gun M5 anti-tank gun, but from a different cartridge case. The “76-mm” designation was chosen to help keep the supply of ammunition from being confused between the two cannon” ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 9, 2017, 5:23pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/7 "2017-10-09T17:23:34Z")
> [@Toledo\_Jim](#): > > But the way the two are chambered, the length of the round, the firing (rimfire/centerfire), the detailed shape of the round can all be different. Rimfire? Why? ---
**Author:** ![AdamF](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/adamf/32/6246_2.png) [@AdamF](https://boards.straightdope.com/u/AdamF)\ **Post date:** [October 9, 2017, 6:54pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/8 "2017-10-09T18:54:25Z")
> [@chacoguy](#): > > Did this ever happen, to the point where it influenced the outcome of a battle? There is one case I am aware of. In 1942, British forces converted German projectiles for their own use. British forces were using US M3 medium tanks armed with 75mm gun. Germans were using early Panzer IV also armed with 75mm gun. The US armor-piercing projectiles were rushed into production and had tendency to shatter when hitting armor. Some engineer had the idea to use the higer quality captured German projectiles. After some machining, he was able to fit them into US cartridges and fire them from the US gun. Apparently it worked so well, about 17000 projectiles were modified. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 9, 2017, 7:13pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/9 "2017-10-09T19:13:06Z")
> [@AdamF](#): > > Some engineer had the idea to use the higer quality captured German projectiles. After some machining, he was able to fit them into US cartridges and fire them from the US gun. Apparently it worked so well, about 17000 projectiles were modified. Two things strike me: The Germans got to try their weapons out on smaller countries before taking them into action against countries with large armies. Having a job taking live artillery rounds apart and putting them into new shells would be a nerve wracking job for me. ---
**Author:** ![Corry\_El](https://avatars.discourse-cdn.com/v4/letter/c/ecae2f/32.png) [@Corry\_El](https://boards.straightdope.com/u/Corry_El)\ **Post date:** [October 9, 2017, 8:39pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/10 "2017-10-09T20:39:25Z")
The case of German 75mm tank rounds\* illustrates two issues which arise in using cannon shells in a weapon other than one for which they were designed: 1. it’s likely you have to have cartridge cases designed for the other weapon. As mentioned this conversion used German 75mm _shells_ in standard US cartridge cases in US 75mm tank guns. 2. with a cannon shell there’s what is called a rotating band, a separate piece which engages rifling in the bore rather than the body of the shell doing it. These German 75mm rounds it happened could be adapted to the US 75mm bore by machining down the rotating bands. That wouldn’t be as practical on a machine gun bullet with no rotating band, the whole bullet would have to be machined down. Although it also would have been more complicated if trying to fire the US rounds from the German 75mm. \*probably the K. Gr. Rot 7,5 cm. The Anglo-Americans particularly liked the relatively large explosive filler in this round v early US APC M61 rounds which penetrated about as well and had space for explosive filler but none fitted yet, besides the M72 solid shot already on hand which had no space for explosive and which tended to break up as mentioned. The Germans decided the round was not strong enough when piercing heavy sloped armor and provided a much smaller explosive cavity in the Pzgr. 39 which some sources, apparently erroneously, assume was the round converted for British use. ---
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [October 9, 2017, 8:56pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/11 "2017-10-09T20:56:41Z")
> [@carnivorousplant](#): > > Two things strike me: > > The Germans got to try their weapons out on smaller countries before taking them into action against countries with large armies. > > Having a job taking live artillery rounds apart and putting them into new shells would be a nerve wracking job for me. Dismantling projectiles from cartridge cases is; but primarily was a routine job. The operations on fixed ammunition were done remotely by machine with explosive barricades/distance. The main hazard was ignition of propellant or primers; not the high explosive/chemical filler detonation/expulsion though that would occur after a slight delay in the event of a fire. Reloaders (hunters/target shooters) have small scale priming/depriming tools. Military and industrial companies have larger scale devices for artillery shells in the fixed or semi-fixed category. For images and explanation; see ammunition pull apart machines. [ammunition pull apart machines - Google Search](https://www.google.com/search?q=ammunition+pull+apart+machines&rlz=1CATAAC_enUS692US692&oq=ammunition+pull+apart+machines&aqs=chrome..69i57.8617j0j9&sourceid=chrome&ie=UTF-8) ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 9, 2017, 9:09pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/12 "2017-10-09T21:09:41Z")
I took apart .22 rounds when I was a kid for the gunpowder. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [October 9, 2017, 9:30pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/13 "2017-10-09T21:30:09Z")
My sister and I dd the same with our father’s 12 bore shotgun cartridges. Gunpowder plus soldier ants = fun…🙂 ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 9, 2017, 10:23pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/14 "2017-10-09T22:23:16Z")
> [@bob\_2](#): > > My sister and I dd the same with our father’s 12 bore shotgun cartridges. Gunpowder plus soldier ants = fun…🙂 Wow. That is real serial killer stuff. We just blew up traffic signs. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [October 9, 2017, 10:53pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/15 "2017-10-09T22:53:40Z")
> [@carnivorousplant](#): > > Rimfire? Why? They were just rimmed cartridges, not rim fire. They were center fire, rimmed cartridges. Dennis ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 9, 2017, 11:11pm UTC](https://boards.straightdope.com/t/82mm-mortar-va-81mm-mortar/798356/16 "2017-10-09T23:11:49Z")
> [@mixdenny](#): > > They were just rimmed cartridges, not rim fire. They were center fire, rimmed cartridges. > > Dennis Thanks.