Kevin Thomas
Well-Known Member
Hey Bill,
Seems to be some misnomers getting tossed around here, but to clarify a "cook-off" is technically impossible in an M60 and I'm pretty sure an M240 as well, at least as long as the gun is functioning properly and being fed from the belt. The reason is simple; the round's never in the chamber until the trigger is actually pulled. Most modern machineguns are open bolt weapons, specifically to preclude this possibility. When you clear an M60 (and many other similar machineguns) the "safe" position is with the bolt closed, to ensure there's no round in the chamber. If the bolt's back, it's ready to rock and roll if there happens to be a round in the feed tray. Bolt closed means the chamber's empty and the weapon's safe. Cook offs in an M16/M4 or other closed bolt weapon are another matter. I've had M16s to the point where the barrels literally glowed a dull cherry red in the darkness, and they will DEFINATELY cook off rounds in that condition. Some one else mentioned the spare barrel and the leather glove (asbestos, actually) that come standard on most heavy machineguns, and they're needed, but not to prevent cook offs. The barrels, not surprisingly, get eaten up pretty quickly if they're heated this badly. It happens, even in training, but it's not good for them and they should be swapped out every few hundred rounds if you're in a sustained fire situation. I don't know quite what happened in that first video, but I don't believe it was a true cook off situation.
As far as the heat damaging the brass, I don't know if that'd be the case with a round that's been cooked off, but I suppose it's something to consider, There's other reasons, completely unrelated to cook offs or heat realted issues, not to use machinegun brass for reloading. In the 30/06, there used to be an entirely different anneal used in cases intended for macinegun use than that intended for stuff that was bound for M1s. Softer neck and shoulder area as I recall, due to the fact that the M1919 BMGs had massive bolts (lot of momentum there) and essentially 'crush fitted" the rounds when the gun fired. Hatcher covers this, but I'd have to look it up to verify the details. In modern 7.62mm production, I'm not sure how the anneal is handled differently (if indeed it is) than that drawn as M118LR cases that are intended for use in bolt guns or match M14s/M21s. The cycling of an M14 is pretty brutal, but it's little more than a love tap compared to what an open bolt weapon does to the brass. You've already learned the lesson, but for anyone else considering it, used machinegun brass is pretty much scrap metal and little more. Unless the zombies are breaking down the door and that's the ONLY brass you have available, there's easier ways to come up with reloadable cases.
Been there, done that, buy the commercial stuff now and to heck with all the extra effort!
Kevin Thomas
Lapua USA
Seems to be some misnomers getting tossed around here, but to clarify a "cook-off" is technically impossible in an M60 and I'm pretty sure an M240 as well, at least as long as the gun is functioning properly and being fed from the belt. The reason is simple; the round's never in the chamber until the trigger is actually pulled. Most modern machineguns are open bolt weapons, specifically to preclude this possibility. When you clear an M60 (and many other similar machineguns) the "safe" position is with the bolt closed, to ensure there's no round in the chamber. If the bolt's back, it's ready to rock and roll if there happens to be a round in the feed tray. Bolt closed means the chamber's empty and the weapon's safe. Cook offs in an M16/M4 or other closed bolt weapon are another matter. I've had M16s to the point where the barrels literally glowed a dull cherry red in the darkness, and they will DEFINATELY cook off rounds in that condition. Some one else mentioned the spare barrel and the leather glove (asbestos, actually) that come standard on most heavy machineguns, and they're needed, but not to prevent cook offs. The barrels, not surprisingly, get eaten up pretty quickly if they're heated this badly. It happens, even in training, but it's not good for them and they should be swapped out every few hundred rounds if you're in a sustained fire situation. I don't know quite what happened in that first video, but I don't believe it was a true cook off situation.
As far as the heat damaging the brass, I don't know if that'd be the case with a round that's been cooked off, but I suppose it's something to consider, There's other reasons, completely unrelated to cook offs or heat realted issues, not to use machinegun brass for reloading. In the 30/06, there used to be an entirely different anneal used in cases intended for macinegun use than that intended for stuff that was bound for M1s. Softer neck and shoulder area as I recall, due to the fact that the M1919 BMGs had massive bolts (lot of momentum there) and essentially 'crush fitted" the rounds when the gun fired. Hatcher covers this, but I'd have to look it up to verify the details. In modern 7.62mm production, I'm not sure how the anneal is handled differently (if indeed it is) than that drawn as M118LR cases that are intended for use in bolt guns or match M14s/M21s. The cycling of an M14 is pretty brutal, but it's little more than a love tap compared to what an open bolt weapon does to the brass. You've already learned the lesson, but for anyone else considering it, used machinegun brass is pretty much scrap metal and little more. Unless the zombies are breaking down the door and that's the ONLY brass you have available, there's easier ways to come up with reloadable cases.
Been there, done that, buy the commercial stuff now and to heck with all the extra effort!
Kevin Thomas
Lapua USA
