I'm changing my M4 handguard from a standard delta nut and KAC style RIS to a Daniel Defense Mk18 style handguard. It's a chinese clone of the madbull rail by the way.
The problem I'm getting is one similar to something I had when changing the Delta Nut in the first place namely that the barrel nut goes on about half a turn and then binds. It can be forced further but needs way more force than seems reasonable. It's a Dytac receiver and I had this problem with an Element delta nut. I ended up going to a King Arms delta nut as that fitted no problem. I'm wondering if anyone else has had a similar issue and what they did to solve it. It almost feels like the receiver threads aren't cut properly somehow.
Any advice gratefully received!