AR Sponsor
Posted: 1/29/2004 7:47:46 PM EDT
|
Ok, here is my newbie question of the week. Is cookoff something I should be worried about? My Olyarms manuals warns me that cookoff may occur if I shoot at a rate of 15 rounds per minute or higher. I have to believe that they are just covering their asses in case it happens at such a low rate of fire. How often does cookoff occur? Is it a real problem? Or should I be worried when I reach round 16 after shooting the first 15 quickly? |
|
Are you sure that is says 15rnds per minute? If so they exaggerated a wee bit. Edited to add: the military fires their M4s (skinny barrel = heats up quickly) at full auto all the time (600rpm-800rpm IIRC) No, I highly dount cook-offs should ever be a problem on a semi auto AR-15 |
|
You can even bet your ass that cook off's can happen, and just like they say. The more a barrel is air cooled by air flow the less you have to worry about. The more it is restricted from cooling the faster it can cook off. Semi auto with one or two mags isn't apt to be a problem, but don't take chances of course, as that can also be governed by the temp of the place your in. An Average of four mags or more can be counted on to cause a cook-off in rapid semi if you leave a rd. left in the chamber, not wise to do anyway as you know. Jack |
|
I have fired my AR something like 300rds as fast as I could load and go.... The gas tube had a low luster red glow to it, showing how hot the barrel and gas tube was. I did this on a couple occasions. I never experienced a cook off. I am not saying it can't happen, however if I remember correct, military manuals state the possibility of cook-off is there after 140-160 rounds fired as fast as possible. *After getting the barrel hot as hell, I never chambered a round and let it set to see if it would cook-off, I just take their word that it will. I may be wrong but the 15rds per minute sounds more like a sustained rate of fire or effective rate of fire so as not to over heat the barrel. |
|
Cook offs while your firing is not what is a concern, as the heat from the barrel heating up the chambered rd. that siting idily there is the dangerous thing on a heated up weapon just in semi. If your firing raoid and not leaving a rd. in the chamber, there won't normaly be anything to worry about as your shooting faster than the rd. will get that hot to cook off. Jack |
| I dumped 11 magazines on burst at our Convoy Live Fire Exersize in January, and had no problems with cookoff, or reliability for that matter. Was more worried about reliability with my issue A2 than anything else. Our commander also had one of my soldiers dump 35 magazines of blanks so we wouldn't have to turn them in, he sat the weapon ejection port down over a cardboard box and did as ordered. The barrel was literally glowing bright red, the cardboard box was smoldering, and we lit a cigarette off the end of the barrel (yes soldiers do stupid stuff... constantly.) and had no issue with cookoff. Perhaps he was feeding the rounds so fast they had no time to get warm, but that's my recent experience. I'll ask a couple of infantry buddies today if they ever saw it. By the way, I'm off to go run 4 miles or so (XXIII Airbore Corps) at PT. Enjoy the civilian sector, you get better equipment when you're allowed to buy your own gear, and don't have to deal with work-induced leg injuries. |
|
When establishing "cook-off" threshold, one must be patient and wait at least 15 minutes with a round chambered in a hot gun before assuming that "after x rounds, this chambered round will not cook-off." However, it seems to me that we were required to wait for a full 30 minutes to increase the "confidence value" of that round number. But I do know the following: When compaired to M16A1 handguards & barrels, M16A2 handguards & barrels had a higher cook-off threshold. Then when we (KAC) got the RAS approved by USSOCOM and then the Army, The RAS's (M4, M5 and RIS) had a higher threshold than the M4 and M16A2 handguards. And in our more recent testing, both the URX and the S.I.R. further improve (raise) cook-off threshold. However, this type testing is something "you don't want to try at home." You know like the car adds: "professional driver, closed course." ...and always keep yopur muzzle pointed in a safe direction... |
|
Is cookoff something I should be worried about? Yes it can be, see the comments by 3rdtk and coldblue. They know what they are talking about. My Olyarms manuals warns me that cookoff may occur if I shoot at a rate of 15 rounds per minute or higher. I have to believe that they are just covering their asses in case it happens at such a low rate of fire. 12-15 rounds per minute is the sustained rate of fire. That is how fast you can fire the gun indefinitely without causing the problem (i.e. all day long). You can fire the gun faster than that without causing problems; but you can't continue to fire faster than that indefinitely. Think of it as a time thing - you can fire much faster (600rpm) than 15rpm for a short time, 30-40rpm for a limited time or slower than 15rpm for a very long time. How often does cookoff occur? Is it a real problem? Again, check out 3rdtk and coldblue's comments but it can occur even in semi-autos if the gun gets hot enough. It may take a ahile for the heat to fire the round; but if you leave a round chambered in a hot rifle it is a possibility. Or should I be worried when I reach round 16 after shooting the first 15 quickly? No, I wouldn't sweat that. Most of the cookoff warnings I've seen refer to dumping 150-180rds of full auto through 14.5" M4 barrels in a very short time period. Still, if you have fired off several mags in a short time period, it isn't a bad idea from a safety perspective to not chamber a round until you are ready to shoot (as an example, don't leave the rifle with a round in a hot chamber sitting on the bench and then walk downrange to check your targets) |
|
Quoted: 12-15 rounds per minute is the sustained rate of fire. That is how fast you can fire the gun indefinitely without causing the problem (i.e. all day long). You can fire the gun faster than that without causing problems; but you can't continue to fire faster than that indefinitely. Dang you beat me to it. Should of posted it last night but I was tired. (Came across the thread at around 0300). This man has the correct answer, and in my experience 4-5 mags bumped we've never experienced a cook off. Stay Safe |
| I went into the US Army in 1972. I never have had an M16 cook off, but I did have it happen with an M60 once. I was at basic training. My squad had been learning to shoot the M60 on full auto at white painted barrels scattered about over a small valley. Everybody had fired the thing and I was the last one up and had also blasted away with it. The DI called for a cease fire and walked in front of the weapon to address the squad. That was not a bright move. He was standing right in front of the M60 stradling it with his legs. You guessed it. A 7.62 round cooked off and shot right between his legs! The blood drained from his face and he looked sick. He started to blame the dumb recruit behind the weapon (me), but he had seen for himself that I was not even touching the M60 when it discharged. I'm sure that he never did that trick again. Watch-Six |
|
If you want to bump fire that many rds. that is a lot of fun, but if you do not remove that last rd.of the 4th or fifth mag., and leave it in the chamber, you will very likely have a cook off. If you are shooting in 10 above zero cold weather, instead of 110 degree heat, you will have less of a chance of a cook off, but would you stand in front of it on a bet? Jack |
|
The M-60 fires off an open bolt. The only way to get a cook-off is to have a round fail to fire and stay in the chamber with the bolt closed. You could also have the extractor fail to pull the round, and that could cause a cook off with the bolt open. I suppose it could happen........... It is more likely that the op rod jumped the sear and fired a round between the guys legs, not a cook off. |
|
Quoted: I'm off to go run 4 miles or so (XXIII Airbore Corps) at PT. I think someone got fat thumbed should be XVIII Airborne Corps. Only had one cook off with my M4. During a night ambush at Campbell during the summer. Dumped 4 mags full auto into the kill zone. Inserted fresh mag and chambered the gun. Weapon was kept pointed down range and on safe. As the demolition team was just about set to go down range that's when I experinced my cook off. Round was in chamber about 30-45 seconds before cook off. |
|
Quoted: The M-60 fires off an open bolt. The only way to get a cook-off is to have a round fail to fire and stay in the chamber with the bolt closed. You could also have the extractor fail to pull the round, and that could cause a cook off with the bolt open. I suppose it could happen........... It is more likely that the op rod jumped the sear and fired a round between the guys legs, not a cook off. Or how about this (actual experience in my Platoon). Viet-Nam night ambush resulted in about a 5 minute fire fight. The M60 had fired a little more than 600 rounds. Then all firing stopped. We began preparing to sweep the kill zone and E&E the area. Then bang! The 60 cooked off while the gunner was preparing another belt for re-loading. When we got back to our patrol base, we took the gun apart and inspected it. The firing pin had broke in two places. So during the afore mentioned fire fight, the now 3-piece firing pin "peened" itself too short (over the course of firing 600 rounds) to indent the primer of the last round fired. Now that is one reliable design of a firing pin! |
|
Thank you one and all for your posts. I suppose the lesson is never leave a round chambered after any sustained firing unless the merde is currently hittin the fan and always keep your loaded rifle pointed in a safe direction. Good lessons for a newbie like me. Thanks for the info. |
AR Sponsor