Educate me on quad rails

[BK14]

I’ve spent my shooting life avoiding quad rails. Vtac/JP handguard on my first AR, about 10/15 years ago, keymod and Mlok followed. Was using an Mlok handguard on my work rifle the last few years, but starting next year my work rifle will have a quad rail.

What’re the nuances? I’ve finally settled on the HTP railscales covers, Carve P hand stop, and the Thorntail 6 with a Cloud rein as my preferred accessories for Mlok, but I don’t know anything about quad rails.

What rail covers, control points, light mounts, sling mounts, etc. are you guys running on quadrails?

[Pnut]

Quad rails are slowly losing popularity with the advent of KeyMod (KM) and MLOK rails. These are my opinions only, but I think it’s due to weight savings, simplicity, and size reduction. I have a rifle that I put a quad on 20 years ago, and recently purchased a rifle with with an KeyMod rail. With the KM rifle, I get a much better grip around the forend. The quad feels like gripping a beer can. The quad is also a meat grinder on your hands unless you ass covers, which will add even more thickness.

I think KM is slowly losing popularity to MLOK.

If you want the slimmest grip area on your quad, go with ladder covers. There many options for QD cup sling mounts or loops for clip style sling attachments.

I can go on and on about accessories, but only you can decide what will work best for you. But keep it simple. When I first purchased my quad years ago, I put every bell and whistle on the thing. It looked like a Filipino taxi cab! Over the years I trimmed it down to just MY essentials… a red dot/magnifier, backup sights, ladder rail covers, a short foreward grip/hand stop, Surefire ScoutLight with tape switch, and qd sling cups.

[breakingtime91]

I’ve spent my shooting life avoiding quad rails. Vtac/JP handguard on my first AR, about 10/15 years ago, keymod and Mlok followed. Was using an Mlok handguard on my work rifle the last few years, but starting next year my work rifle will have a quad rail.

What’re the nuances? I’ve finally settled on the HTP railscales covers, Carve P hand stop, and the Thorntail 6 with a Cloud rein as my preferred accessories for Mlok, but I don’t know anything about quad rails.

What rail covers, control points, light mounts, sling mounts, etc. are you guys running on quadrails?

I either run mine slick (centurion) or with magpul ladders. Also have a bcm foregrip on it for a reference point and to shoot off barriers. I tend to use whatever light mount I can get that places the tail cap at 11 and puts the light head just infront of the muzzle. Arisaka, impact weapons, or the new surefire mounts work well. Quads are thick and not as comfortable usually compared to mlok but man are they awesome. One thing I love is the heat resistance I get compared to a skinny mlok rail. Never have to wear a glove with my quad raid, two mags in and my bcm mcmr is red hot. If you are using NV, quads are all I would do anyway. To many stories from friends using light weight mlok rails that are thing losing zero from bumps and hard drops in the field. I feel like the new Daniel defense mlok rail is a good compromise, thicker and wider then the trend of the super thin rail.

[theJanitor]

What kind of rifle and rail are you being issued? Some rails are very thick, while some are narrow, like the DD Omega. I like quads, as they are grippy, not hot, and accessory placement is much more tunable than with Mlok or KM. That’s being said, I no longer have any 1913 quad rails

[rob_s]

I still prefer quads, frankly. Particularly those like the original Daniel Defense and similar that have a narrow profile. I like to put the Larue or Magpul snap-on covers over the part I grip, and ladder covers over most of the rest.

IMO they heat up slower due to the greater mass, and in turn dissipate heat better because of all the surface area.

I did some weight comparisons years ago and IN USE they weren’t appreciably heavier than kitted-up slick tubes (what I always called “Brazilian” ).

I agree with the above poster it would help to know what specific quad-rail you are being issued (although honestly I’m not up on what’s currently available).

Quote a lot of old-busted in this gun I suppose.

[LittleLebowski]

fore thickness.

I think KM is slowly losing popularity to MLOK.

Keymod has been dead for years.

[TGS]

Quadrails for life, yo.

The prototypical qual rail is from Knights Armament, called the RAS (Rail Adapter System). It is a drop in rail for use with a FSB and not free floated. This is what most people think of when they hear quad-rail, and is what has been used by the US military on M4 carbines for the last 2 decades as well as being featured on the Mk18 Mod 0.

A free float rifle length option is also available, and is what was used on the Mk12 Mod 1.

The quad rail that you see on the SOCOM Block II M4 as well as the Mk18 Mod 1 is the RISII (Rail Integrated System II) made by Daniel Defense. The advantage of the RISII is that it is free floated, widely regarded as being the most durable rail system, and on the M4 allows the M203 to be mounted. It is a two piece rail, and relatively heavy. It also looks badass on the Mk18, since it is a 9.3" length and butts up right against a suppressor mounted on a 10.3" barrel.

The RIS II was the last rail to be popular; while still widely used by the military and LE (don't fix what ain't broke), everything since then at the institutional level has been a step towards MLOK.

IMO, if a user required a rail and wanted it to be the most efficient system available, I'd say that's the Daniel Defense DDM4. It is a free float one-piece rail unlike the RIS II, and is significantly lighter than the RIS II or KAC RAS; it's weight is actually quite competitive with most MLOK rails. Unlike the RIS II and KAC RAS, it has built in sling QD points. It also has a very narrow diameter giving ergonomics more like the popular MLOK rails, whereas the RIS II is fairly wide and the KAC RAS is just chunky in general. Here's the DDM4 on my Daniel Defense Mk18. It's objectively a better choice for a "working gun" than the RIS II, but I swapped my RIS II back onto it just because it makes me giggle and it's a "fun gun" for me anyways as I don't use it at work.

We issue the Daniel Defense Mk18 with the RIS II, and while I like it, I would 100% swap them out on a work gun for the DDM4 if allowed. It saves a ton of weight.

That's my primer on quad-rails for you. There's a lot of other options, some really weird, but I'd focus on these to begin with. I've owned and been issued several of each of the above.

As for rail covers, I've had a bunch and have a very strong preference for the Daniel Defense rubbers. As in, I won't buy anything else unless it's a clone, like my Mk12 which has the KAC RAS with the old school plastic KAC rail covers.

[oregon45]

What's the consensus regarding Centurion Arms' C4 quad rails? They look like an interesting "drop in" option that also free-floats the barrel.

[OlongJohnson]

I obviously don't have the operational experience of a lot of guys here, but as a mechanical engineer who designs, builds, analyzes and improves stuff, I like the BCM QRF and MCMR. I'm a fan of the mounting system, although I've found a little TLC not described in the manual may be required for a perfect installation. The QRF is 0.22 inches larger than the DDM4, but with XXXL hands that make a USP .45 FS "just right," that's no problem for me. The specs on the respective web sites indicate the BCM QRF-12 weighs exactly the same as the DDM4 12 inch.

I have a OG KMR that's super-light on a pencil barrel build from back in the day, and the only reason I keep it is it's so light. The complete flattop came in at 5 lb, 10 oz with a Magpul CTR and no special parts other than barrel and handguard selection. Could go several ounces lighter just by swapping to a different buttstock.

[shootist26]

What's the consensus regarding Centurion Arms' C4 quad rails? They look like an interesting "drop in" option that also free-floats the barrel.

Very happy with mine. I got it years ago because it allowed for easy installation onto my pin and welded barrel. It's very good quality and yes it's heavy and pricey