Skip to the bold for the specs.
It's actually 11.1" the threads on a noveske barrel are .6". So while the above poster may have got his asr mount to work I on the other hand had to cut down a 12.5" barrel to 11.75" to get the SiCo trifecta mount to work.
I'm actually having a hard time believing the above poster. Iv done my research and I'm not the first person to want the NSR Rail to work and mate with only a slight gap. Also you need some room between the rail and the suppressor for barrel whip. And just in case you think I didn't think of it yes a spacer would work but it would.have to be about 1/4" and that's pretty big when the threads are only. 6" long. Also the spacer may cause the mount to not be true or concentric.
I don't know what your planning but I hope this all helps. So nsr rail 11.1" the 11.5" barrel minute the. 6" threads equals 10.9" so the threads recess. 2" under the rail.