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Yankee Hill YHM-230 Gas Block Riser


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Some of the upper rail height gas blocks that are available look like they should be able to handle the ABS plastic of the Magpul MBUS's.

PRI is longer than a normal gas block, and the contact area of the sight is passed the gas tube.


JD Machine is vented across the side.


MI has a a vent drilled through the center as well.


I'm not saying that they are perfect, or guaranteed to work. I have the MBUS mounted on a PRI, and I plan on using this set-up as soon as my carbon barrel is finished.

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I'm still on the fence if I'm for or against this.

I've searched high and low and could not find one post/pic/video of a MBUS melted or deformed on a GB.

On the contrary, I have found several posts and pics of people who have successfully mated the two together with no complaints or reports of damage.

While I understand the caution, and the liability to Magpul, I see this as an extreme situation circumstance. Perhaps in an extended, full-auto, fire fight would you see temperatures hot enough. At that point wouldn't you have to worry about the MOE handguard, which is also attached at the barrel/GB??

I only spent $40 on my front sight. I've already made (and lost) much more expensive gambles on this rifle build. If I manage to melt/deform/damage my MBUS by mounting it on a gas block, I'll make sure 308AR has the first pictures and details about it. I just bought another case of Port 7.62, so I should be able to stress this test out a bit!

FWIW, I will also try to do this on a 5.56 Adams Arms piston block too...

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  • 1 month later...

I agree. They dont want to warrantee it. Probably doesnt melt, maybe performance is affected, point of impact, locking and actuation etc. Regardless in my case I only use the MBUS on my .22. I prefer other sights

I agree it probably won't melt.  I doubt it would be affected much at all...if it is the right type of thermo-polymer compound.

I nominate you to test it out!  <munch>


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The problem I had with my coyote[rifle not pet] with carrying handle to zero had mag-pul flip frt. raised pin almost all the way out put a .5" riser under to much, difference between reciever rail and gas block was a strong 3/16" just got correct gas block flip up. Zeroed at 100yrds. with pin screwed all the way down worked out fine.Ran hot barrel during summer with mag-pul on didn't melt just couldn't zero at 100.Shoot on bro.

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If I had anything with a gas block pic rail, I'd try to melt one.  If anyone wants to donate that gas block - temporarily - I'll donate the front MBUS for the test.  I'll try to melt the thing to goo...  <thumbsup>

I'll send your gas block back, but it might be slimed.  Just sayin'...  <dontknow>

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Thinking about this some more.

Having lived in a pretty rugged desert for most of my life, upon reflection, I believe I now know what will happen if you mount one on your gas block.

After years of happy service and you telling everyone you know how nothing will happen, you will go to raise the now crystalized plastic body to an upright position, only to have it crumble in your fingers.  Your astonishment will only be compounded by the fact that part of the sight and mounting hardware will stubbornly refuse to budge from its position on the gasblock, while the sand-granules that used to be the other part of the sight body stick resolutely to your fingers while simultaneously smearing the color of the plastic across your skin...never to be removed but shed with dead skin cells over a period of a month.

Better listen to Mag-Pul.


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Can't say how many times I've gone to grab something with plastic on the handle, to have the plastic crack and then pinch, or just crumble apart.

Of course, this IS the desert.  <thumbsup>


Absolutely.  The UV here is hard on parts - kills motorcycle master cylinders pretty damn fast. 

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