XCR Forum banner
21 - 34 of 34 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #23 ·
around .25" thinner then my mlok handguard (also were last years mlok handguards actually 1.52" that doesn't sound right, mines at least 1.75" and I got this handguard last year, I dont have a good way of measuring it tho).
also how's the height now too? cause it looks like it cut off a little height as well. my current mlok height is somewhere around 2.5"

Also the most important question, how long was the wait time from ordering it and receiving it?
 

·
Registered
Joined
·
80 Posts
Been staring at that picture for about a month now...

OK, got out the rifle to change and locktite the little bolts of the rail covers from 3/8" to 1/4". Did not successfully find shorter bots for the sling mount.
Shot a picture of the calipers across the width of the rail. 1.5225" with my thumb holding the calipers too tight while pressing the camera button with my left hand. Would be 1.524" without the pressure on the thumb wheel of the calipers. This rifle was billed and shipped at the end of November of 2021. Ordered at the end of March of 2021.

Calipers Temperature Measuring instrument Material property Gas


That's a difference of .006", or the thickness of one and a half pieces of 20 pound copy paper.

After a month of staring at that picture, and those rifles were both being manufactured in 2022, I'm thinking that if there was a change, it was in the depth of the cut between the rail positions (1:30, 4:30, 7:30, and 10:30 positions), resulting in an optical illusion that the rail surface width changes...

...or that the different angle of the two rifles created different shadows, making it appear that the rail width is different.
 

·
Registered
Joined
·
23,047 Posts
6 thou....or 2 human hairs, lol.
 

·
Registered
Joined
·
203 Posts
So why are the M-Lok slots so thick on the hand guard? I have M-loks on other things and they aren't that thick. Is it to match a specified depth that's supposed to be standard for M-Lok?
 

·
Registered
Joined
·
23,047 Posts
So why are the M-Lok slots so thick on the hand guard? I have M-loks on other things and they aren't that thick. Is it to match a specified depth that's supposed to be standard for M-Lok?
I'd say yes. Mlok has a thickness requirement.... When you combine that with the ability to quick change the bbl and pull it with the gas block buried, it probably creates a minimum ID size that may be larger than an equivalent AR with it's smaller gas block, but I'm completely guessing. Just looking at the lower portion of the gas block doesn't give me the indication that it's markedly bigger than an AR one.
 

·
Registered
Joined
·
80 Posts
I poked around some...

MLOK was invented by Magpul. They do not show a patent on the rail, and there are notes saying the rail pattern is free use. Magpul licenses the use of the MLOK name. So it sounds like anyone can make a rail using the slot pattern, but must pay Magpul if they want to identify the pattern as MLOK.
Magpul does have patents on every possible thing you can attach to that rail, and the little nuts that hold those things onto the rail. And they have trademarked every name of everything. Patents run out in 22 years, and trademarks can be renewed for as long as they are in use. So that is a long-game approach to making money.
Most of the drawings for the rail show only the length and width of the slots, shape of the corners, and spacing between. Then the back side of whatever attaches and the little nuts. The only drawing I came across that has a section marked with the little arrows that point to the side and the letter "B", does not have the drawing of the section included.

There are drawings of rails from different makers of floating hand guards, and they ignore rail thickness or width of the hand guard (beyond one saying 1.5 inches), and seem most concerned with a spec for the air gap between the barrel and hand guard, and the depth of the slot for the gas assembly above the barrel.

The standard bolts for the MLOK rail covers, sling mounts, and Picatinny rails to mount to the MLOK rails seem to be 3/8 inch, and too long for the XCR. 5/16 would be better, but apparently not made in low socket head cap screws, and I wanted a fully coated bolt that would not rust on the end like if I sanded it with the belt sander. I ended up with quarter inch.
So, it appears that the XCR has thinner than standard rail cross sections, that leave more bolt sticking out than other rifles and hand guards. And a minimum clearance between the inside of the hand guard and the barrel.

Whatever the end of the hand guard width discussion, plan on buying a bunch of 1/4 inch long socket head cap screws to replace all the 3/8 inch long bolts that come with all of your MLOK accessories.
 

·
Registered
Joined
·
23,047 Posts
Thanks for all that research!

McMaster has 5/16" long 10-32 in ultra low profile head socket, just not in the regular low profile ones:


EDIT Youch! $4.12 each apparently though. Not cost effective. Thought at first it was $4.12 for like 10.
 

·
Registered
Joined
·
13 Posts
View attachment 15719
Here's what my calipers are measuring on one of the newer thin M-LOK handguards. While I really, really love how the thin profile feels in the hand, I can't remove the barrel unless most I remove most of the attachments on it. Even railscale covers pose an issue.
Thanks everyone for taking the time to give feedback and share good information.

For me personally I do not plan on ever changing calibers and or removing the barrel.

Since I will not be removing the barrel, will all accessory attachments like grips and lights etc. still attach to the new thinner M-LOK handguards ?

With the new slimmer M-LOK handguard, will standard Magpul M-LOK Screws hit the barrel when the T-Nuts are tightened all the way down or will the screws cause an issue only IF you try to remove the barrel ?

If the screws do touch the barrel, could they just be sanded down a bit and still hold properly ?

Thanks again for any feedback.
 

·
Registered
Joined
·
23,047 Posts
Thanks everyone for taking the time to give feedback and share good information.

For me personally I do not plan on ever changing calibers and or removing the barrel.

Since I will not be removing the barrel, will all accessory attachments like grips and lights etc. still attach to the new thinner M-LOK handguards ?

With the new slimmer M-LOK handguard, will standard Magpul M-LOK Screws hit the barrel when the T-Nuts are tightened all the way down or will the screws cause an issue only IF you try to remove the barrel ?

If the screws do touch the barrel, could they just be sanded down a bit and still hold properly ?

Thanks again for any feedback.
The ONLY issue there has ever been is when removing the bbl, the extension may hit the bolts for some Mlok accessories depending on the bolt length. I just buy shorter bolts if this is an issue.
 
21 - 34 of 34 Posts
Top