I bought couple of these Mini bbl'd actions in 6.5 Grendel from Legacy - one with the std wt bbl, the other with their hvy bbl. Have yet to fire a single round of 6.5 Grendel ammo through either of them. I pulled the 6.5 bbl from the std wt model, and replaced it with a Bartlein 1-8tw 6mm bbl in light Palma contour that I finished at 24", chambered for the 6RAT, which is very similar to the Grinch. The biggest obstacle was getting a stock, which I was finally able to order from McMillan. They initially told me there would be a $500 charge to model the inlet for this action, but when I checked back with them a few months later, they said they'd had so many requests for stocks for the Mini that they'd do it at no additional charge, if I'd send them a bbl'd action to work off of. Eventually, I received a Sako Varmint model stock from them, which fit the action & bottom metal (plastic) really well. I put the hvy bbl bbl'd action in a Boyds ProVarmint laminated stock w/adjustable cheekpiece - did have to remove a minor amount of wood in the bbl channel, but otherwise, it was also a great fit, and made a really sharp-looking minature tactical rifle. However, I sold it before ever taking time to shoot it, so can't comment on the accuracy of the factory 6.5 bbl.
The little rifle in the McMillan stock is accurate enough to be a lot of fun to work with - used a Warne 20 MOA scope rail to mount an Athlon Ares 4.5-27x50 mil scope, and swapped the OEM HACT trigger for a Timney, which required a bit of plastic to be cut out to make the trigger slot longer in the DBM. Really looking forward to getting the stock back for this rifle - had to return it to McMillan to repair some bubbles that had come up through the gel coat.
CDI is now making DBM that is actually made of metal - and that uses MDT magazines that may allow loading rounds a little longer than the OEM DBM. It also moves the mag release latch to a spot behind the mag well, which would be a big improvement over the former point just in front.