Thats odd this is what I read on the front page description when I bought mine.
" MR-1 features the power and rigidity to remove 30 pounds of steel per hour and the accuracy and precision to hold tight tolerances". I didn’t see that part about having it out in the hundred thousand range is maybe the best its going to get. I never would have shelled out over 8K for that.
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I get it. I’m sure if its out that much they will replace any parts that need replacing. I wasn’t trying to poke at you. Its not a $50,000
5000 lbs cast iron machine. Any problem that I have had were handled very quickly by Langmuir.
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I would say with a little patience these are easily enough trammed within .005" over 8" or so from what I’ve seen on my unit. Just picked up toward the end of March. And I know I’m nit picking the thousandths for a machine that I’ll probably only want to be within .010" for the projects I’ll do on it, but if I can dial it in better, I’ll definitely give it the effort. Too many years in the trade to just let it be I guess 
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After a late night in the shop I’ve checked out the best I can think of on the machine. After disassembling the top end down to the X rails and mounting the mag base dial indicator on the bottom X rail block and indicating along the upper rail on the front and top sides I could pick up the twist. Roughly .0035" foward on the top rail from left to right and about .002" across the top, looking like it has some twist, either from the machining op fixturing or material relief machining it after welding. Used feeler gauges to check for contact between the rail and gantry and had a few spots toward the middle that a .0015" would slip into, but the ends were tight as a drum.
I popped the rails off and disassembled the gantry to bring to the shop I work at. I’ll get it fixtured on one of our horizontal machines and check it out. Will update later with my findings.
Disclaimer: This is probably more than close enough for the average home gamer. I work with much tighter tolerances on a daily basis, so these few thou will be in the back of my mind every time I take a cut. No need for most people to be this precise for home projects.
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Skipshift, Please keep us updated. Curious how this turn out. 
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Well, here’s the run down, sorry for the wall of text.
There was a couple thou twist in the gantry as suspected. That combined with the mounting surfaces of the carriages not being 100% square and level was making for some tricky readings.
Got the gantry fixtured on a mill and skimmed .003" off of the upper linear rail mounting area to get it cleaned up. Also ended up taking around .002" off of the mating shoulder to square it up. Doing this naturally means you’ll have to re-shim the Z axis to get it square again.
The carriages were only out of parallel by .0015" over 3.5", so not terrible but a contributing factor. I got those fixtured on the linear bearing surfaces and decked them ~.004" total to get the heights even and squared.
There is still a bit of twist when everything is assembled, which as Langmuir has stated there is a tolerance stack up from each component that will only let the machines get so close to perfect. Without re-machining every surface it’d be hard to really get this thing laser flat, and at that point with man hours involved you might as well buy a different machine if you need that much precision.
End result: I’m sitting at a total variation to all 4 corners of ~.002".
.0015" from front left to back left, .002" from front left to back right, and .0008" from front left to front right.
It’s not perfect, but I wouldn’t expect a machine in this price bracket to achieve the same precision as my production mills in the machine shop.
Doing some test cuts on various 6" long pieces in the vise was showing around .001" parallel after flipping the part and facing the second side. In hind sight I could flip the part from front to back and reduce that number even more. Even so, that is not a bad number for a machine aimed at the hobby market imo.
I’ll be curious to see how close other folks manage to dial their mills in. I know there will be some unicorns that hit it almost dead on but I’d be interested in seeing the average machine’s squareness.
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Glad you got it sorted out.
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For those that flycut your baseplate, did you generate your own tool path for it or does Langmuir provide one? (If so, where did you find it?)
Unfortunately, it appears I have the same issue as @MichaelBarker where my baseplate is too far back in the machine in order to use a 1/2" end mill (a 1/2" cutter is 1/8" short of the rear of the baseplate). Long story short, my chip tray wasn’t straight or square in any way, so when they recommended to put the baseplate in at 8-9/16", I split the difference and it ended up not being good enough. 
I figure I’ll flycut with as small of a cutter diameter as I can get away (thinking 0.75") with to minimize tilt/nod leaving grooves. I bought the SST spindle gauge… but hoping to avoid the rabbit hole of chasing ever increasing precision.
I generated the program and fusion 360.
If all you need is a single pass across the back, just do it manually.
- With the flycutter installed, home the machine - this should place the flycutter over the area to be cut.
- Manually turn on the spindle - 2000 rpm
- Lower the Z until the flycutter kisses the high spot. Go slow. Use .010 and .001 increments when you get close. Depending on width of baseplate you might need to move to the right to kiss the baseplate.
- Keep lowering Z (slowly) until you have the depth for your first pass.
- Switch to continuous jog and set it to 15-20 IPM
- Press and hold the right arrow key.
- Travel all the way across the plate while watching the travel limit for X.
- Stop when the flycutter stops cutting, flycutter it off the baseplate, or close to the X travel limit.
- Select .001 step - assuming you are taking off the material in more than 1 pass.
- Lower Z for the second cut (make sure you are on .001" step - not cont). For the final pass you might want to use .0005" step to lightly kiss the machined surface you want to match.
- Press and hold the left arrow key to pass the flycutter over the baseplate.
- Stop once the flycutter is done cutting, off the baseplate, or close to the limit switch.
Rinse and Repeat…
I used this manual control to surface my oversized baseplate… Just make sure you don’t hit Z down when you are close to the baseplate and in CONT step mode.
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I ended up generating a tool path with Fusion with a 0.001” depth of cut. So far so good. I found the high spot and am just going to take it down 0.010” at a time until I’ve got it all flat. At the very least, it was a good kick in the butt to get the CAD/CAM pipeline all set up.
It was kind of clunky and awkward to generate because Fusion really wants to have a full tool diameter + some margin away from the stock and there is not 2”+ of space on both sides of the baseplate for that travel.