js_paddle07
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I have it mounted to the gas block on my M&P15OR. I've fired quite a few consecutive rounds and the sight hasn't melted yet.
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Magpul MBUS polymer front sight hasn't melted yet...
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cyphertext
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It isn't going to melt into a gooey mess after a few shots, but it may melt ever so slightly to where the sight is canted and it can lose zero.
ETA: My fear would be that it would melt the threads on the sight post where I could no longer adjust it.
ETA: My fear would be that it would melt the threads on the sight post where I could no longer adjust it.
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Vinney47
Member
You're just tempting fate. From Magpul themselves, from the MBUS Front site product page under the "specs" tab, at the bottom:
"NOTE: Cannot be mounted to a railed gas block due to excess heat issues.
Front MBUS must be mounted to a railed fore end on the same plane as the receiver rail. "
MBUS® SIGHTS - MBUS® - Magpul® Back-Up Sight ? Front
But it's your money...
"NOTE: Cannot be mounted to a railed gas block due to excess heat issues.
Front MBUS must be mounted to a railed fore end on the same plane as the receiver rail. "
MBUS® SIGHTS - MBUS® - Magpul® Back-Up Sight ? Front
But it's your money...
OP
js_paddle07
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I think some 'tests' have been done and it holds up fine.
Vinney47
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As much as we all want the zombie apocalypse to happen, it probably won't, so sustained rapid fire won't be necessary. As long as you don't push it too much, sounds like you will be alright I guess
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JaPes
Member
If not, all he's got to do is scrape off burnt on charred goo off his railed gas block.
Vinney47
Member
I know this is taking the thread in a slightly different direction and I don't mean to be insulting to anyone.... but...
Why?
If you have a quad rail, move the plastic sight back a few notches so it's off the gas block. If you have a standard handguard and have to mount your front sight on the railed gas block, get a metal one! It may not have the "magpul" name on it, but there are several folding metal front sights within the price range of the MBUS. And if you must have Magpul, they now have the MBUS Pro which is all metal, albeit at a higher price.
Again... why put the polymer on a railed gas block, knowing full well what the risk is? WHY take that risk and give yourself a self imposed limitation on rate of fire? It's really unnecessary, given the other options.
I 'suspect' the problem would arise with a combination of a high rate of fire and high ambient temperatures.
Testing would probably give you an idea of a safe rate for a given temperature, but this assumes you can afford to stay within the limits.
For casual shooting this might be fine, but what about sights on a gun that may see combat? You wouldn't want to find that your backup sight had failed just when you needed it most.
Testing would probably give you an idea of a safe rate for a given temperature, but this assumes you can afford to stay within the limits.
For casual shooting this might be fine, but what about sights on a gun that may see combat? You wouldn't want to find that your backup sight had failed just when you needed it most.
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js_paddle07
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All valid points. First off, the sights were on the rifle when I bought it, so I didn't choose to add polymer sights.
Secondly, I feel like the sight moved back and an empty gas block just wouldn't look good.
Thirdly, I want the longest sight radius possible. I even have my rear sight as far back as it will go, so it actually lays over the charging handle when it's folded (I can still grasp the handle and chamber a round though).
Lastly, yes, I anticipate a zombie apocalypse and welcome it's arrival. But I feel that the majority of my personal zombie slaying will be close quarters where aiming isn't nearly as important. A melted Magpul sight will be the least of my worries.
Vinney47
Member
JaPes
Member
paddle,
If you ever get a chance to try Troy folding battle sights, do it. They are pricey, but they are great.
If you ever get a chance to try Troy folding battle sights, do it. They are pricey, but they are great.
shawnfergie
Member
Get the new magpul front (metal) sight.... sell off the front mbus.
MBUS® SIGHTS - MBUS® Pro - Magpul® Back-Up Sight ? Front
MBUS® SIGHTS - MBUS® Pro - Magpul® Back-Up Sight ? Front
rojodiablo
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The Magpul and ARMS and related sights have a lot of graphite in the plastic which keeps the plastic from goo-ing down, they tend to get brittle and crack like an old electrical receptacle.
Get them hot, and keep them hot; the P.O.I. will shift a little. But the issue is when the rifle gets bounced; the sight cracks and crumbles.
Ask me how we know......
I will give them their due; they put up with a LOT of nonsense before they fail outright.For a casual shooter, there is no issue unless you have a mag-dump fetish.
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js_paddle07
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The Magpul and ARMS and related sights have a lot of graphite in the plastic which keeps the plastic from goo-ing down, they tend to get brittle and crack like an old electrical receptacle.
Get them hot, and keep them hot; the P.O.I. will shift a little. But the issue is when the rifle gets bounced; the sight cracks and crumbles.
Ask me how we know......
For a casual shooter, there is no issue unless you have a mag-dump fetish.
Military use?
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js_paddle07
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Well it appears it doesn't fit my quad-rail anyway. I have the cheap Ade Advanced Optics rail installed. A light, bipod, etc. attach fine. But I tried to move the MBUS front sight back to the rail just to make you all happy 
, and the screw would not fit in the slot. That rail is supposed to be picatinny/weaver. I wonder why it doesn't fit??
, and the screw would not fit in the slot. That rail is supposed to be picatinny/weaver. I wonder why it doesn't fit??cyphertext
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You may have answered your own question. Is the rail a Picatinny (MIL-STD-1913), or is it Weaver mount? They are different, with different measurements. Just out of curiosity, try mounting it on different spots... maybe the slot you chose is out of spec.
Nitrous SSC
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Certain parts on a gun should not be plastic. Your sights are one of them. Everything about the weapons effectiveness is tied to the sights.
cyphertext
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Tell that to Glock, H&K, Sig, S&W, and any other manufacturer with a polymer hand gun.
Magpul sights are very effective, when used per the manufacturer's instructions. Not a very exhaustive test, but the MBUS did fair better. Back Up Iron Sight Drop Test | Kit Up!
ETA: Not a MBUS fan, but for reasons other than durability.
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js_paddle07
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I use a red dot as my primary sight. You are correct in your assessment though -- when my red dot goes out at the range or gets hit from enemy gunfire, it will be imperative that my back up sights are metal so I can return accurate fire and make it to the truck alive.
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js_paddle07
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I'll do that tonight and see if it fits. Thanks!
Nitrous SSC
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Last time I checked the factory sights on my M&Ps and other polymer hand guns are steel mounted on a steel slide.
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js_paddle07
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Glock factory sights are in fact plastic, and have been performing quite well for a couple decades.
cyphertext
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Glock factory sights, at least gen3 and earlier were plastic. The S&W SDVE handguns have a plastic rear sight. Many firearms have plastic sights without issue.
You guys crack me up with plastic sights and Mickey Mouse rails, waiting for the Big One to happen and thinking you will depend on your cheap plastic toys to get you through. 
Buy something decent and depend on it. Feel good knowing you have something decent and not made by Fisher Price.
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Buy something decent and depend on it. Feel good knowing you have something decent and not made by Fisher Price.
.
cyphertext
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You guys crack me up with plastic sights and Mickey Mouse rails, waiting for the Big One to happen and thinking you will depend on your cheap plastic toys to get you through.
Buy something decent and depend on it. Feel good knowing you have something decent and not made by Fisher Price.
.
Says the man who buys M&P Shields!
Polymer is just a fact of life with firearms now. One could buy different sights than Magpuls, like I have, but for others they work just fine. They are meant to be backup sights, not primary sights.rojodiablo
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Actually, ANY optic which takes a direct rifle hit will come apart; regardless of the material it is made of. If the optic holds together fairly well??? It's usually doing so a couple feet away from the rifle.
The poly sights are really durable. We might not like that, being fans of metal.... but it is the truth. (I am NOT giving up my 9504 for a Glock; I gotta draw the line somewhere!!)
I run the ARMS sights; I have Magpul on 1 rifle, and Knights' on another. The ARMS sights have taken a couple drops; I dunno; maybe 10 feet was the worst. I was impressed, the rifle bounced a bunch, and the sight was a bit mangled looking. Works fine- 2 years later. The plastics have the ability to flex more and return to shape vs. bending. The sheer strength of the steel sights is not at issue; the problem is bending if a hard landing is the meal served up.
We cooked an ARMS sight on a 308's gas block. It was there for several seasons. A lot of rounds and heat. The bottom half cracked and crumbled. I can't complain; the barrel would get well past too hot to touch without serious gloves; plastic foregrips would be getting stinky and smoking; the sight must have been much hotter given it's direct contact. If the optic had not been on a very high use rifle, I am certain it would have held up for a half of forever.
