I often keep reading that military forces destroy the ammunition or weapons that they captured from the terrorist/illegal organizations (ISIS, Taliban, Al Qaeda and other groups in Syria etc.)
As I know, ammunition is expensive. Not all types of ammunition is expensive though. But still they can use the captured ammunition and guns for themselves. We all do that in video games 
You want to be shot by your own side because they’re shooting at the sound of an “enemy” gun?
Or run out of ammo and the guys you’re with have the wrong ammo?
They buy ammo “on the cheap”.
Expired stuff, third-rate stuff–often not safe to use.
Is ammo captured from terrorists reliable? Who knows how old it is, what conditions it was stored under, who made it? It is not a good idea to rely on munitions that may not meet milspec requirements, or with questionable chain of custody.
Same reason most sport/competition shooters don’t use ammo found at the range. Don’t know who made it nor how it’s loaded. Could be a maximum load rifle round that wouldn’t be safe in your gun.
for one, it’s pretty likely of a cartridge type that our armed forces don’t use. the US standard battle rifle (M16/M4) fires 5.56x45mm NATO. A lot of the rifles floating around those areas are Eastern Bloc stuff like the SKS and Kalashnikov-pattern (“AK-47”) rifles. they fire 7.62x39mm or 5.45x39mm Soviet. plus most of it is cheap steel-cased and/or steel-jacketed bullets. that stuff is widely available on the open market.
there’s little benefit to keeping it, and destroying it means it can’t fall back into enemy hands.
Not all ammunition is interchangeable. Nor, as Fear Itself specifies, may it be safe to use. Current standardized ammo is manufactured to specifications; using non-standard ammo can lead it to potentially jam or damage the weapon (using a ‘hot’ load can stress the chamber, causing it to eventually fail and “violently break open in your face.”) Headspaces or shoulder dimensions may be different, projectile weights may be different, etc.
That, and I don’t have the time/wherewithal to process this captured stuff into the inventory*, and I don’t want it to be scavenged by the enemy for re-use. Thus, the C-4 process comes into play.
*Note: It takes an asston of paperwork to re-absorb ammunition into the inventory. Easier/better just to make it go away.
Tripler
War is not a video game.
A bit off topic: In the Korean war the US had a covert operation to replace some Korean ammo with rounds designed to explode on firing. It doesn’t take much, if one round from a case blows a soldier up, no one else wants to use that ammo.
Dennis
I was reading an article about the making of the original Robocop. There’s a scene in which *Robocop *invades a drug warehouse and fights it out with a couple of dozen shooters. It’s all cut in quick takes - a burst of gunfire here and another there. That wasn’t the way it was supposed to go, but they found their guns kept jamming after three seconds of use, so they *had *to cut away quickly.
Guns need lots of care, and military guns especially are used in harsh conditions. Every war throws up investigations afterward because guns don’t work right. The M-16 rifle in Vietnam was one of the most ignominious.
That’s guns rather than ammo, true. Others have already covered the reasons why captured ammo is problematic.
In America, police forces are tending toward destroying captured guns. There have been too many incidents of guns getting back into the hands of criminals, a lot more cheaply than they were bought for.
IIRC a big contributor to that was the Armalite design had very tight clearances for increased accuracy, and was the first personal weapon the armed forces were using with such a mix of materials (aluminum for the upper and lower receiver, steel for the bolt/bolt carrier and barrel.) while the Kalashnikov was much looser, but (as the story goes) you could bury one in mud for a month, fish it out, rinse it off, and it’d function perfectly.
can’t hit the broad side of a barn with one, though.
Actually, it was a change in ammo( the powder, I believe) coupled with the Army not issuing cleaning kits.
Define, “they”.
Everything that has already been stated in this thread is absolutely correct. But, with that said, I can relay anecdotal evidence that sometimes “they” do use captured ammunition, guns and equipment. When working with the Iraqi Army in 2007, they would scrounge up ammo and stuff we’d find in weapons caches all the time. Like kids in a candy store… or rather, like needy kids at a Red Cross soup van! We’d try to advise them against the practice, and warn them of the dangers of doing it. Especially of the chance for booby traps. But without fail, anytime a cache was uncovered or dug up, they’d start scooping up anything and everything useful, especially ammunition, and even more especially, belted ammunition for their machine guns. They were still using all the same soviet era weapons that the enemy was using, so there was no issue in compatibility. It was a bit frustrating because we’d want to get an inventory of everything for the report or debriefing, but they’d sometimes grab it all before that was possible. It was a chore to keep them away. Not surprisingly, one such cache of weapons and ammunition had a nice tactical flashlight among it’s contents. The Iraqis started scavenging the cache before we could stop them. Happy and giddy as can be, one of them grabbed the “torch” and turned it on to see if the batteries worked. The batteries definitely worked, though they weren’t connected to the bulb. Instead, insurgents had stuff the flashlight body with HME and connected the batteries to a blasting cap. Dude blew his hand off.