Fitting HAO SMR (Geisselle Style) Rail to NGRS 416D

[km2339]

Hi all,

As above, I have the rail, I've taken off the sling loops at the front. But the rail just will not fit over the barrel nut. I've tried lube, and as hard as I dare hit with a hammer and wiggled every which way. Any one who's done this know if I'm missing something? Or does it just need dremmeling?