this is still an issue I guess......back in late 2013 I had built my first AR15 and was then looking into an AR10 to build, and I ran into all the differences / components etc.....in Jan/Feb 2014 I was starting to collect parts and 2 years ago most upper/lowers were backordered and when a SunDevil mfg set came up in their "devil coat" on a local social media gun site, offered by a local national guardsman / FFL holder seller, I kept my eyes out and ended up buying it for 550$, then scoured the web trying to figure out exactly what height my upper "was" and "needed" in the form of a handguard. SunDevil says their slick side upper uses the post 8/2009 "low" rail height at 1.253 so after searching I went with APEXMACHINE 15" rail for the post 2009 rail [ with the bore to rail measurement at 1.253] I actually wanted another rail, [Sampson I think, but it was 2 years ago, so not sure now] however it wasn't available in the "low" height so this is what I went with. I had already bought most everything else before the handguard so I was kinda chomping at the bit so to speak to get it done. I had changed handguards twice on my AR15, ending up with a Diamondhead and I also wanted it for the SunDevil receiver but they indivated it would be a while, so I bought the APEX and I have the same issue as the OP, it is "NOT QUITE" and exact match, but I cant machine anything and was doing other things and didn't want to by several 200+ handguards just to get one to fit "exactly" so im living with it, a couple pics but with my crappy iphone4 so hopefully you guys can see the slight difference in the rail to guard height. I want to build another with the Diamondhead guard for a 308 but most uppers I see are still backordered and are the DPMS "high" or pre 8/2009 height [APEX states the "high height is 1.313 at the center bore to rail] Diamondhead says theirs is for the "low" height at 1.250 "range" lol. still looking for an in stock upper/lower set and then I will have to choose I guess......
