I don't mean to dogpile but I'm in agreement with Mike_AK; one can utilize Volquartsen and Ruger parts to create a Mamba that will be just as reliable and accurate as if Volquartsen had assembled it themselves. It's obvious that there are some folks who just aren't up to the job of procuring parts and assembling a pistol from them and would prefer to have their pistol already assembled, then there are those who dive in head first and purchase everything to assemble themselves. Both will create the same result.
There is nothing magical about the Volquartsen grip frame; it's simply a housing for Volquartsen internal parts,
the very same parts that are sold to the public.
There is nothing magical about Volquartsen assembling Volquartsen parts in a completely OEM Ruger grip housing;
no special gnomes build them, just people like you and I.
What you're paying extra for with the Mamba is simply the assembly and testing (hopefully) of the pistol before it arrives at the dealer for transfer to its new owner.
Below is what I'll refer to as my RVQ, which is a Scorpion clone (sans the VQ grip frame), built from a Mark II grip frame and Volquartsen LLV upper, Competition bolt, Competition Kit, and Hogue grips. It shoots lights out and is just as accurate and reliable as
any Volquartsen assembled pistol - it has to be because there's absolutely no reason why it shouldn't, other than operator error and/or improperly assembled parts.