Cheese Graters 2021

[1168]

As far as the anti-rotation, the tabs are a little bit far away from the receiver for my liking. I guess they were trying to allow for the tolerances of thicker billet receivers, but it wound up making the tabs kind of worthless, as they allow for one or two millimeters of rotation before impacting the receiver. While I have never had mine rotate, that would be my one complaint.

My RIS II is exactly like that, on a billet or forged upper. I’ve had it for 10 years, no issues. There’s the USGI guns, also. Intellectually, I’m certain that DD rails are solid, but I agree that the tabs are not confidence inspiring.

[ExplorinInTheWoods]

I still like quad rails, if you can find the old seekins SAR3 quad rail it’s nice, very lightweight, has built in QD points. It is a little taller like the DD light rail. I have a BCM quad rail that I’ll be putting on another build.

[JediGuy]

As far as the anti-rotation, the tabs are a little bit far away from the receiver for my liking. I guess they were trying to allow for the tolerances of thicker billet receivers, but it wound up making the tabs kind of worthless, as they allow for one or two millimeters of rotation before impacting the receiver. While I have never had mine rotate, that would be my one complaint.

I picked up a CMT MLOK handguard in the EE with a cracked anti rotation tab. After getting that squared away with JB Weld (not a hard use gun, so, yeah), I still had to file down the interior of the other tab to get square to the top of the receiver. After that experience, I understand and appreciate some build in tolerances.
Of course, for the designated NV upper that will eventually have a laser, I used a URX4.

[Uncas47]

KAC RAS with SAS lower rail.

[Randall]

Just looking at the drawing on DD’s site https://danieldefense.com/ddm4r-rail...id-length.html, the DDM4 12.0 (very poorly named) is 2.165” tall and 1.9” wide. With ladders, that would be suuuuuper close to a KAC URX4 with Magpul covers. My DD RIS II https://danieldefense.com/m4a1-risii-black.html measures 2.24”x2.24”, and as noted the top rail stands more proud than the bottom, giving it a pear-shaped cross-section, which seems best, at least for me. The BCM seems to fall about halfway between on width, but might be a little taller https://www.m4carbine.net/showthread...-QRF-quad-rail, which would make it more similar to the Centurion (which I still need to play with).

Based on this thread: http://www.300blktalk.com/forum/view...80872&start=30, it looks like the add-on rails for the URX3 stand proud of the built-in rail sections, so there’s that. This thread: https://www.ar15.com/forums/ar-15/Th...-1-/12-740078/ contains the only dimensions I could find on the 3.1. They are of the smooth part in the middle, and the implication is that it is bigger in cross section than some of the others discussed. Can I get someone to measure width and height from pic-rail peaks at the muzzle end?

How’s the anti-rotation on the DDM4? As good as the RIS? Better? (Edit: https://www.m4carbine.net/showthread...-MFR-DDM4-Rail) I sure wish it wasn’t more than twice the price of the BCM.

Edit: fixed link

I just mic'd a DDM4 12.0 / Lite Rail III and it matches DD's website. Bare rail measured 2.16" x 1.90". With ergo ladders on all sides that increased to 2.26" x 1.99".

I havent verified the weight of the 12.0, but my 10.0 matched the website, although they dont include the weight of the barrel nut (0.9oz), bolt up plate (0.5oz), and 4 screws (0.4oz)

Between the DD and the BCM QRF, I personally prefer the shape of the DD though that could just be a familiarity bias. I didnt have a lot of time with a QRF but it definitely felt wider.

[99cobra2881]

More pic whoring of the mk8 upper on its first conjugal visit to see its Socom 556 thats in jail.

Its still relevant to the discussion, the mk8 is a solid choice and accepts accessories very well.

[1168]

I just mic'd a DDM4 12.0 / Lite Rail III and it matches DD's website. Bare rail measured 2.16" x 1.90". With ergo ladders on all sides that increased to 2.26" x 1.99".

I havent verified the weight of the 12.0, but my 10.0 matched the website, although they dont include the weight of the barrel nut (0.9oz), bolt up plate (0.5oz), and 4 screws (0.4oz)

Between the DD and the BCM QRF, I personally prefer the shape of the DD though that could just be a familiarity bias. I didnt have a lot of time with a QRF but it definitely felt wider.

Excellent post; thanks.

More pic whoring of the mk8 upper on its first conjugal visit to see its Socom 556 thats in jail.

Its still relevant to the discussion, the mk8 is a solid choice and accepts accessories very well.

The Mk8 is certainly relevant here, and is probably the only Mlok of its kind.

[17K]

The Centurion C4 MLOK is pretty close.

[kyjd75]

The Centurion C4 MLOK is pretty close.

Yep. :agree

[1168]

https://www.cmttac.com/quad-rail Just found out this exists. 1.96" wide x 2.195" height According to the site. Pic looks symmetrical in height for top and bottom rails.