The rail I am leaning towards for this is the DD LITE Rail III. There are a few limitations BUT I think it is overall the best design for this application. It is lighter than the DD RIS II for the M4A1 by 4.5 oz (within 0.5" length comparison) and is 0.1 oz lighter than the Geissele MK8 M-Lok ( 0.55" difference in length). Limitations are that the LITE Rail III and the MK8 do not allow bottom access to the barrel behind the gas block for mounting M203 but this is not a requirement (that I could find) outlined in the M4A1+ statement and is not in the requirements I outlined primarily due to the availability of other options in place of the M203. I really like the bolt up plate style handguard to barrel nut interface but admittedly I have no data to show that it is any stronger then the MK8 method. Both methods provide a rigid continuation of the receiver and have engineering in place to prevent rotation.
I agree with the quad rail statements and while I do agree that DOD issues out some precious items to PFCs I also know that little accessories can and will get lost. I like the simplicity of the quad rail for this application given that it would be GPF issue and not specifically SOF.
All that said, I really like the MK8 and have one sitting on my desk in the queue for a build.
ETA: I prefer both the MK8 and LITE Rail III to the RIS II due to the fact they are both solid rails and not two part systems. I have been able to find a couple of times where RIS II lower section was fractured because it was not supported all the way to the muzzle end of the rail. This could be overcome (and may have) with some engineering work but it is a limitation of the system that is not longer required when excluding the M203 requirement.
I agree with the quad rail statements and while I do agree that DOD issues out some precious items to PFCs I also know that little accessories can and will get lost. I like the simplicity of the quad rail for this application given that it would be GPF issue and not specifically SOF.
All that said, I really like the MK8 and have one sitting on my desk in the queue for a build.
ETA: I prefer both the MK8 and LITE Rail III to the RIS II due to the fact they are both solid rails and not two part systems. I have been able to find a couple of times where RIS II lower section was fractured because it was not supported all the way to the muzzle end of the rail. This could be overcome (and may have) with some engineering work but it is a limitation of the system that is not longer required when excluding the M203 requirement.