The markings on my DD M4 barrel says “DD 4150 MP 5.56 NATO 1/7”. I have a DD lightweight coming next week and I will see what it says.
I don’t think that the fact that a manufacture is not doing HPT/MPI should an indicator that that their products are substandard. However If the rejection rate is 3%, does that mean that there is a lot of rifles out there not making Gov. standard?
How many companies are doing HPT/MPI anyway? Colt, FN, BCM… those are the only ones I can think of off the top of my head.
Here is a youtube video on Magnetic Particle Inspection that explains the process.
http://www.youtube.com/watch?v=4P3DzZzXwa8