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Posted: 1/6/2012 4:23:28 PM EDT
What upper would be best for sustained automatic fire - and be cheap? 
The M16A2/A3 is not an LMG and I don't intend to buy an LMG upper but, what configuration would be something inbetween a LMG and assault rifle - kind of like the role the HK M27 is supposed to fufil? I want to shoot long bursts on a barrel that will hold up to it. Also, the next question is - is there a way I can cool such a weapon down other than letting it air cool? |
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Heaviest barrel you can find for not too much money.
Fluting can help cooling by increasing surface area. Get a porous/open-top handguard system to maximize airflow over the barrel. Lock the bolt open when not shooting to encourage airflow through the barrel. If you didn't get it TOO hot, you can quick-cool it by dousing it in liquid of some sort (usually water). If you got it to too hot, though, repeated heatings and quenchings like that will affect the crystalline structure of the metal, making it harder and more brittle. FWIW, getting it too hot and letting it air cool can result in slow annealing of the barrel, making it more flexible, but softer. So, if you're gonna quench it, don't get it glowing. |
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Quoted:
What upper would be best for sustained automatic fire - and be cheap?
The M16A2/A3 is not an LMG and I don't intend to buy an LMG upper but, what configuration would be something inbetween a LMG and assault rifle - kind of like the role the HK M27 is supposed to fufil? I want to shoot long bursts on a barrel that will hold up to it. Also, the next question is - is there a way I can cool such a weapon down other than letting it air cool? A used one. (No, I'm serious!)
Find a used blaster grade beater upper, check to be sure that it's still safe with headspacing and all, and go nuts. It'll be cheaper than buying a new upper and burning through it. Mike |
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My blaster uppers are mostly LE trade-in Colt uppers. Fer instance, one is an M4A2 with 14.5" barrel, 100% Colt; lots of cosmetic wear but the chamber/bore look like it had never been shot. Cost me $325.
I just take two or three on every range trip, and rotate them out when they get hot. You'd be amazed at how much ammo you can go through this way, and I've never personally melted a gas tube. But if you want to do long bursts, get a watercooled M16 upper. They are impossible to melt. Here's one that Scott built: 
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| Any cheap upper will work fine, heavier chrome lined barrels of course are better for sustained fire. I also have an MGI upper which is the only quick change barrel upper. Swapping out barrels when hot will require gloves though. It is easier just to swap out cheap uppers instead. |
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Quoted:
Heaviest barrel you can find for not too much money. Fluting can help cooling by increasing surface area. Get a porous/open-top handguard system to maximize airflow over the barrel. Lock the bolt open when not shooting to encourage airflow through the barrel. If you didn't get it TOO hot, you can quick-cool it by dousing it in liquid of some sort (usually water). If you got it to too hot, though, repeated heatings and quenchings like that will affect the crystalline structure of the metal, making it harder and more brittle. FWIW, getting it too hot and letting it air cool can result in slow annealing of the barrel, making it more flexible, but softer. So, if you're gonna quench it, don't get it glowing. Does it matter what kind of treatment the barrel has had (chrome lined, melonited, etc), can you still end up annealing the barrel this way. How do you find out if this has happened to your barrel and what can you do to remedy the situation? Sorry about the bombardment of questions, just wondering if I've been doing this to a few of my barrels..... |
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Quoted:
Does it matter what kind of treatment the barrel has had (chrome lined, melonited, etc), can you still end up annealing the barrel this way. How do you find out if this has happened to your barrel and what can you do to remedy the situation? Sorry about the bombardment of questions, just wondering if I've been doing this to a few of my barrels..... If you get it hot enough to affect the metallurgy, coatings or treatments won't matter - but the treatments can affect how long it takes to heat up, and how well it handles regular wear. Your first clue that you got it too hot will be the barrel visibly glowing... hard to get it there, and hard to miss if you do. In fact, I've only ever seen it happen on a beltfed (M60), but that doesn't mean it couldn't be done. To see if you managed to do that kind of damage, you could have your barrels tested for hardness at critical hotspots like just behind the FSB. If it's softer or harder there than, say, the thickest part right by the barrel nut, or near the muzzle, you've managed to screw up the metal. If you've gotten there, I guess it's possible for the barrel to re-hardened and drawn down correctly - though I'm no heat treat expert on doing that to precision finished pieces. It'd probably be more expensive, too, than just getting some new blasters. |
| I don't think I've had my barrels glowing, so I'm pretty sure I haven't done this. I stick to the short 7.5" barrels for blasters and still have a few in the safe from Sabre Defense before they folded. So I'm good for awhile, but thanks for the info, I never knew about the poosibility of annealing barrels accidentally |
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Quoted:
What upper would be best for sustained automatic fire - and be cheap?
The M16A2/A3 is not an LMG and I don't intend to buy an LMG upper but, what configuration would be something inbetween a LMG and assault rifle - kind of like the role the HK M27 is supposed to fufil? I want to shoot long bursts on a barrel that will hold up to it. Also, the next question is - is there a way I can cool such a weapon down other than letting it air cool? What do you consider to be a long burst? 50-100-500 rounds? |
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Quoted:
Didn't PSA have FN m249 style lined barreled uppers? you mean like stellite or just double chrome lined? OP easiest way to keep stuff cool is to just switch uppers. For prairie dogging though I've used a Co2 bottle with a couple of lines coming off of it. Get the barrels really hot (still not mag dump hot but similar principle) and crack to valve so it bleeds co2 through the barrel. Seems to gently cool the barrel and seems to have extended the life of some of the hotter calibers we shoot (.22-250 ackley, .220 swift, etc.) never really tried it on the 16 with the exception of the one time I put the JP upper on it. Easiest way to cool something safely and simply is to just have a mister bottle of water to spray on it if you get it cooking. |
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