I purchased the BMAS Triple Mount to attach to my Bushmaster 16" M4 barrel (Patrolman's barrel).  However, once I installed it I noticed that it was canted upwards at a noticeable angle compared to the barrel.  I removed it and double and triple checked everything and re-installed it and it was still canted upward.  Even with a little brute force before tightening the screws I still couldn't get it to level out.  As best I can tell the forward-most bottom part of the front sight (where the front taper pin is located) protrudes lower than the Triple Mount is made to accomodate and is what's "pushing" the back end of the Triple Mount down and causing it to cant upward.  I'm not too familiar with AR-15s so I can't say whether this is an out of spec front sight, an out of spec Triple Mount, or whether it's just not compatible with my barrel.

Has anyone else had or heard of the same problem?  If so, or if you have an idea as to what I'm doing wrong (the BMAS directions were only 3 steps, I sure hope I'm smart enough to have followed them correctly), please let me know.  I'm hoping it's just a stupid mistake on my part because I really like the setup of the Triple Mount and would hate not to be able to use it.  Any help would be greatly appreciated.

Here's a pic . . .

http://mysite.verizon.net/res0ydxi/bmastriplemount.jpg

There are two things that could be wrong with the mounting of your triple mount. First, I can see from the photo that you are using the .750” bushing set. There is a small groove cut around the shoulder (outside diameter) on the .750” bushing. This is wrong for your barrel, try the .720” bushing set that should have been included with your kit. Second, it appears in the photo that the mount is too far back and resting on the rear lug. Make sure to pull it forward so it does not hit the rear lug at all.
If you still have this problem after making the changes above it is possible that the bayonet lug was removed incorrectly. One way to check this (After making the changes above) is to tighten down the mount so that it still moves but is not loose. Rotate the mount on the barrel, there should be a little movement in either direction. If there is no movement then the dimension from the center line of the barrel to the bottom of the milled surface on your front sight is to long.  
I hope this helps you out if not feel free to contact me at [email protected]

Archer, thanks for the help and suggestions, but it still doesn't seem to be working.  I changed to the .720" bushings, which were almost impossible to get in there (even when using a screwdriver and pliers), and I moved the mount forward so it wasn't near the rear lug.  Unfortunately it's still canted up, although not as much as before.

I was going to try to rotate the mount on the barrel as suggested but even before putting in the screws it is so tight (with those .720" bushings) that it doesn't move at all.

I have to get ready for work now but when I get home I'm going to try to remove the mount, but I have a feeling that'll be an ordeal since it's so tight now.  Any other suggestions are welcomed and again, thanks for helping out, it's wonderful when a company is out there offering this kind of assistance with their products.

Here's the pic with the .720" bushings and the mount moved forward . . .
[img]http://mysite.verizon.net/res0ydxi/bmastriplemount2.jpg[/img]

There is one more thing you can do to check if it is the mount. Move the mount out onto the front section of the barrel (completely away from the sight) and tighten it down. It should be straight. I would suspect that it is an interference problem with the front sight. Let me know how you make out.

Yeah, one of the first things I did after I noticed the cant was to mount it towards the front of the barrel and it was level then.  That's what originally made me think it was a problem with that forward part of the sight protruding too low.

It took quite a bit of work to remove the mount and .720" bushings from my last attempt pictured above and I managed to scratch the mount and bushings up pretty bad in the process, so it looks like the triple mount is going to be a no-go for now.  Oh well, thanks again for the help and suggestions Archer, I really do appreciate it.