View Full Version : Magpul MBUS mounted to gas block

Metal god
November 1, 2012, 04:58 AM
I went to the range today . I've been wanting to do this test for awhile and I finaly had my chance

I have the sght mounted to the my gas block ( against the recmmendations of Magpul ). My plan was to fire 100 rounds quickly through the gun to get the gas block and front sight very hot .

I started by making sure the Iron sights were zeroed and then fired a five shot group ( the entire test was conducted at 50 yards ). Unfortunately I lost or misplaced that target . I can tell you they were on target about 3 MOA .( 2 low-2 high and 1 dead center )

I then fired 100 rounds in 82 seconds ( timed ) . When I finished the barrel was smoking and I could smell something that smelled alot like plastic burning :eek: Here is the front sight right after the test and the target I shot . I had the front sight down cus I was using my red dot to stay on target for the test .

Yes I know Im shooting high I was also running a test on my red=dot at the same time .

I let everything cool down and fired a five shot group again . Here is the target ( it's the group on the right ). As you can see the shots are high and to the left . Not uber bad but this is only at 50 yards . At 100 yards that would be a big time mis .

I then re-zeroed the sights and they seemed to work fine . The front sight is still solid and operates just fine but IMO it did lose zero .

November 1, 2012, 05:46 AM
Cool test. I wonder how it would have done if you were using the MBUS as your sight while shooting instead of the red dot? Would it have shifted as you were shooting?

BTW, isn't it cool to know your rifle works great! :)

November 1, 2012, 10:13 AM
Did you examine the MBUS for evidence of melting?

While Magpul recommends against a gas block mount, I have yet to see anybody actually try and see exactly what it takes to melt one.

Metal god
November 2, 2012, 08:14 PM
I took the sight off last night when I was cleaning the rifle . It looks good I could not see any melting or deformations . All the edges , angles and flat areas seem to be normal . There is no discoloring it seems fine as far as I can tell .

November 4, 2012, 07:17 AM
Interesting test, thanks for posting.

November 4, 2012, 10:44 AM
I bought a Windham Weaponry SRC and when I picked it up at Cabela's I bought the Magpul sights and went home to mount them and sight in the rifle.
When I opened the package for the front sight I saw the warning about not mounting it on the gas block. I contacted Windham Weaponry for their opinion and a WW gunsmith emailed me and told me that he had tested the A.R.M.S. #71 polymer front sight on a gas block. The A.R.M.S. sight has the same warning about not mounting on the gas block as the Magpul MBUS sight.
Erik (the gunsmith) told me that he had slidefired 6 full 30 round magazines, one after another, before the A.R.M.S. polymer sight showed any signs of melting.
He told me that semi-auto firing would not cause any melting so the Magpul is a good low cost alternative.

November 4, 2012, 11:09 AM
Good info in this test Metal God. I'm guessing we'll be referring people to this post for a long time.....

November 5, 2012, 01:43 AM
I put it on my gas block of my Windham SRC and it was fine. But I was breaking in the barrel and waiting for my hand guard to come. Now, it is on my hand guard, just so I don't risk anything.