I just bought a Model1 Sales 24" bull barrel upper with a standard free float tube and a bolt on single rail gas block on it.  it has a sling attachment on it.  I was wondering what the best way to attach a bipod to it is.  The diameter just in front of the block is .936.  Thanks

Have a sling stud mounted to the bottom of the free float tube for the use of a Harris bi-pod.  Mounted anywhere other than the tube, you defeat the purpose of the free float...

+1

I recently went through the same issue. As a solution I drilled and tapped a hole on the bottom of the free float and mounted a swivle stud for a Harris bipod. I had one lying around but YHM sells a machine threaded swivel stud that is just what you need for this job. if you do it your self be sure to mount the stud back far enough that the Harris bipod will not hang over the end of the tube.