My first 6.5mm Grendel Project - after 3 .223 Rem AR-15s

[Kohoki]

Hi there,

I registered here because all the german gun forums lack of sufficient information about this young and potent caliber. After some experiences with custom .223 AR15s, (DMR556 & SBR556 (yes, they are allowed in Germany) I am planning my first 6.5mm Grendel Rifle and hope to receive some advice or hints from all you professionals out here. Maybe I start with the setup I planned by now, here comes a list of the parts I like to use:

Upper Receiver: VLTOR MUR 1A
Lower Receiver: DAR - DAR Lower Advanced
Handguard: GenIII Delta Carbon Fiber Forearm Rifle Length Black
Top Rail: Gen III Delta Forearm SPR Straight Top Rail rifle length (does anyone know the height this rail adds to the flat top receiver?)
Barrel: 20" Lothar Walther 1 in 9 twist (what twist would you recommend? My intention is to use heavier bullets)
Barrel Extension: Les Bear Custom
Bolt: Alexander Arms
Bolt Carrier: DPMS M16 (due to its mass)
Gas block: Noveske Switchblock 5.56 Rifle length (I know, there is one available for 6.8SPC, but only in Midlength, do you think the Switchblock will work?)
Stock: MAGPUL UBR was my first choice, but maybe a standard A2 is suits that concept a little bit more, what do you think?
Trigger: Geissele High Speed Match
Charging Handle: Rainier Arms Raptor™
Mag Release: Norgon Ambi Mag Catch
Magazines: AR-Stoner 10 rd
Grip: TangoDown Battlegrip
Muzzlebrake: GUNWORKS VAULT762 - not released yet
Scope: Schmidt & Bender PMII / LP
Scopemount: ERATAC BlockMount

This is my first approach, what do you think? Did I forget something? Does anyone know who sells the corresponding reamer like this one from PTG?

Thank you very much in advance for all your suggestions!!

@Mod
I am not quite sure if this posting is at the right place here, feel free to move it to a more appropriate place