Jose - thank you for your interest in our Troy Bravo rail. Unfortunately, this will not work on your HK MR556. To install our Bravo rail will require a mil-spec barrel nut and this firearm has a proprietary barrel nut which will not work with this rail. Troy rails mount to direct impingement gas operated firearms only. If you have questions about this, or any other Troy Industries' products, please shoot us an email to "sales@troyind.com".
The rail comes in black.
Yes. the Troy 13in Bravo Rail is manufactored in the USA.
The Troy 13in Bravo Rail STRX-BR1-13BT-00 will not work with a piston driven upper.
If your Armalite is an AR-15, yes. If you are looking at an AR-10, it would not be compatible.
The ID of the BRAVO rails is 1.39”
Yes, this will fit the Colt LE6920 series M4.
That would depend on what gas block you currently have on your M400. Please contact us at techsales@opticsplanet.com with that information and we will be happy to assist.