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Modifying Upper for M-LOK

27K views 88 replies 13 participants last post by  Biff1212 
#1 ·
Just finished milling off the side and bottom rails on my XCR. I'm just waiting for the specs on the M-LOK slots before I turn this thing into swiss cheese.
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#13 ·
I received my M-LOK QD attachment as well as a picatinny rail section and went ahead and machined one side of the receiver. Turned out great! everything fits very well. There is about .050" clearance between the inside of the receiver and the barrel. No problems installing or uninstalling. I have not machined the inside flat to accept the nuts but I do have a tool coming for next week for that. I would say that the flats don't even need to be machined but I am going to do that anyway once the cutter arrives. I just wanted to get slots in there so I could check clearance on the barrel.
 

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#23 ·
I've looked at various Canadian sites and couldn't find anything that would be an issue regarding shipping of firearm parts. This part is not the serialized receiver so it is not considered a firearm. It is also a non-restricted firearm in Canada so it doesn't have the registration issues. Are there restrictions on the US side?
 
#31 ·
I don't have any M-Lok system but looking at the pictures it seems that you have to be able to get to the back to hold the nuts while tightening the screws to lock them down.
Is there a way to machine a larger hole/s into the slots like the KeyMod to have the nuts already loosely installed and everything can just slide in? Then have a maybe 1/16" channel on the back of the slots to 'hold' the nuts as the screws are tightened?

My questions and ideas maybe have no base, but again I don't have any M-Lok to go by, only pics. ;)
 
#34 ·
Like Mechanic says... see image below. Picture a square with two rounded corners (diagonally opposed). As you tighten and turn the nut 90 degrees, the squared corners butt up against the edges of the slot. Pretty simple and elegant solution.

However, this is where it can get awkward, if you don't stage the length/depth of the t-nut right so the squared corners butt up against the slots, you can spin until the cows come home. Keymod is more fool-proof in this regard. Minor difference. Not a deal breaker.


 
#35 ·
So what is the feeling here among the XCR Commandos, is Keymod or M lock the wave of the future. Will one go the way of Beta tapes and the AMC Gremlin? I personally like keymod, but am having a difficult time telling which way the gun world is headed. I imagine Magpul swings a big hammer. What are your thoughts?
 
#37 ·
Keymod is public domain which means one does not need to jump through any hoops to incorporate it into their products. M-LOK is licensed, albeit royalty free, so requires some legal compliance. Some companies seem to avoid M-LOK.

M-LOK seems to be more flexible as far as positioning options and certainly provides opportunity for innovative design like the previously identified QD rail sections. Personally, I like the look of M-LOK better than Keymod. I don't think either are going away anytime soon.

Standardization is not a simple process. I'm guessing we'll see additional attachment designs come along that improve upon shortcomings in both M-LOK and Keymod.
 
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#38 ·
I think eventually M-LOK will win out....but I prefer KM. IMO, it looks better and there's less problems with the nuts locking as designed....even if there are slightly fewer options on positioning. I've now dealt with a couple of T-nuts like this on unistrut....and frankly, they don't work worth a shit in certain instances.
 
#39 ·
I liked AMC and the Gremlin could be hotrodded.....
 
#41 ·
The Javelin was their slickest car, the AMX was pretty cool too. Don't forget they owned jeep and also did the Eagle wagons and hatch backs. Had a buddy that had a hatch back eagle, he lifted and put buckshot mudders on it, had the straight six--would go anywhere!
 
#42 ·
The Javelin could be hotrodded even better ;-)
In highschool one did really well against a Mustang Mach 1.
Good enough that the Mach 1 didn't make it through the turn - or anything else ever again.
 
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#44 ·
Right.
Dude lost the Mach 1 in the corner, slid it sideways and caught a light pole midlength on the passenger side. Folded it up nicely. Surprisingly, he walked away from the wreck.
He said he had only got it up to 120 when it started sliding.
It was the talk of the school for at least a few weeks.

I knew the guy with the Javelin pretty well. Never wanted to drive behind him going up a hill on a rainy day......
 
#45 ·
Wasn't it the AMX with the "power grabber" hood scoop that was motorized to go up and down. That shit was cool back in the day.

A turn in a Mustang? They weren't designed for that! The '69 and '70 were good (especially the 429 Boss), but the '70s was a rough period for autos. I think Datsun and Toyota confused them. Ford made the Mustang II, not one of their finer moments.
 
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