I saw a list of the different bayonet numbers (M#) with a list of what rifles that they were designed for, but I can't find it again.  Does anyone know, or is there a website talking about the different bayo types?

Is the M7 and M9 the only two designed for the AR15/M16?

What will fit on a 16.1" Colt M4 Upper?

-Red-

None will on a 16" barrel with a standard flashhider.  But if you use one of the XM-177 look-a-like flash hiders that slip over the 16" barrel and make it look like an 11" barrel with a 5" flashhider, the bayonet should fit.  The only reason it wouldn't would be if the outside diameter is larger than a normal flash hider.  I do not believe thay are, but I have never measured.

The slipover supressors I have seen and used are larger diameter than a standard so you will not be able to use one of them!

I will add that a 11.5-inch upper with a 5.5-inch supressor will also mount a bayonet.

As for Bayonets that fit the M-16...  The M7 and M9 are the only US military bayonets but there are MANY others around that will mount to the rifle including some that are actually AOW guns that shoot.  Following is a bayonet that I own that I really like!

[url]http://www.eickhorn-solingen.com/frame_products.htm[/url]

Cool stuff on that website.