I hear it oft repeated that the reason the Soviets used an 82mm mortar design because that way they could use captured enemy 81mm ammunition stocks. However, it seems that there would be two problems with this. First, the fact that there’s now a gap between the projectile and the tube means that propellant gasses can escape, reducing your velocity. Second, the fact that there’s now a gap between the projectile and the tube means that projectile stability is in question, which means your accuracy is in doubt. For example, I can fire a 9mm from a .40S&W pistol, but your velocity is dumped by half and the bullet tumbles in flight.
Is this simply a rumor that’s been repeated so often that it becomes fact, or is it truly the reason behind the Soviet design?
Well, mortar rounds are made to fit loosely. If they were tight, air under them would slow shells sliding down the barrel too much to reliably hit primer with enough force to ignite it. Mortars never were supposed to be very accurate weapons. So I would guess that you can use 81 mm round in 82 mm mortar and don’t lose much of accuracy.
But.
Mortar rounds are cheaper than dirt. Well, nowadays they aren’t so much, with modern design, advanced fusing devices and so on. But in the days of WWII it was just cast iron shell filled with cheaper explosive available (usually amatol) and with simple contact detonator. With mass production it would cost probably less than two buck apiece. I seriously doubt that capability of using enemy supplies of mortar rounds ever was of any concern from strategic point of view.
I have been told that the North Vietnamese had a .51 caliber machine gun. This allowed the use of our ammo but not the other way around.
Puppygod said that this didn’t make much strategic difference, and is probably correct. But it could make a difference here and there and I suppose that is the reason for this.
My mom was dating a former Green Beret when I was a kid. He said that he’d been training Montagnards in the use of mortars. He said there was some sort of demonstration that was being put on for the ‘brass’. Either his team or another fired their mortar – and it went straight up! The people watching all ran for cover. Fortunately, the team had forgotten to install (or set?) the fuse.
I can’t vouch for the veracity of the story, but that’s how he told it.
SandyHook, the NVA would use Soviet heavy MGs, which are chambered for 12.7x108mm cartridges. The cartridge being fractionally **longer **that the M2’s .50 cal would explain it being popularly called “.51 cal” . But (Edited after Preview) as per TM’s Wiki entry, it would would be questionable how well it would operate with M2 rounds – a mortar can have loose tolerances but something that fires from a closed bolt will be a lot pickier as to what it’s fed.
One other pop explanation I’ve commonly heard for oddball calibres in Russian/Soviet ammo, is that often the actual physical bore calibres would be some prevalent standard, with a different casing configuration depending on application and which they’d just call some caliber number off by +/- 1 or 2 mm so that they would reduce the risk of the supply chain getting confused between same-caliber rounds of different types.
I was going to post in here, but puppygod has kind of hit the nail on the head. Besides, you can always close up the gap of one millimeter with flexible obturator bands and such. 1 mm gap? Not so bad. 10 mm gap? Yeah, that’d kind of leave an unarmed mortar in the tube.
Tripler
I doubt that 10mm gapped mortar would even be centered up enough to hit the primer.
The Soviet 82mm design did allow (or would have allowed) advancing troops to use captured NATO 81mm mortar rounds. The Soviets even had a separate firing table for use with the NATO rounds.
The untrue rumor mentioned above was in regard to the .51 caliber N. Korean weapon/round, not to crossover use of 81mm/82mm ammunition.
It wouldn’t make any sense at all, from a North Vietnamese point of view. There was never going to be any widespread need for the Americans to use NVA ammunition, so why would they change calibers just to prevent the other side from using their ammo? If they expected to scrounge American ammo, the logical thing to do would be to just use identical .50 machine guns so at least the captured ammo would work correctly.
