Quote Originally Posted by LinemanBob View Post
I am considering something similar. I have the MSR 15 in 223 wylde and would like to replace the entire upper to a 300blk. I know my MSR 10 is mostly propietery but I think the MSR 15 lower is mil spec.
I would want to replace the entire upper so that I can change back and forth easily. Has anyone tried this?

Yes, it’s easy to do this. The MSR15 is the same as any other MilSpec AR15. Savage doesn’t even make all the parts. They source the the parts from the same sources as nearly every other MilSpec AR. So just build another upper. Let me know if you need any help. I can tell you where to get all the MilSpec parts inexpensively. Or you can go super premium for more $$.