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"Which Free-Float Rail System Should I Buy for my M4?"

The addition of a free-float rail system to any AR-15 pattern carbine is generally one of the first things that many users add to their new rifle.  While at one time there were very few makers of such things, in today's market the options can be dizzying.  Interestingly, two of the earliest players in this market are still, in my opinion, the top picks for this type of rail.

First, why free-float?  As anyone who has shopped for such forends knows, the free-float designs are always the most expensive.  Most people then begin to try to rationalize away why they don't "need" a free-float system and why they are better off with a non-free-float rail that simply bolts in to the position of the stock handguards.  Usually the first argument they use is something along the lines of "I'm not looking for long-range precision accuracy, so I don't need a free-float rail".  This is based, however, off an incorrect assumption that this is the only advantage to a free-float rail, carried over from the idea of free-floating a barrel from the stock on a bolt-action rifle.

Real world advantages for a free-float system on an M4-pattern carbine include the heat-sink properties, the ability to keep sling pressure off the barrel, the ability to mount optics or lasers to the rail, and the overall general increased sturdiness of the free-float system over one that is not.

The selections below are all based on use on a typical carbine-length, or 7"+/-, gas system like that found on the military M4 and the vast majority of commercial variants.  All of these products are also available in a 9" length for mid-length gas systems that are ever-increasing in popularity.  The suggestions remain the same, with the only differences being the (obvious) increased weight of each due to the longer length.

Also, many users are choosing to install rail systems that extend past the gas block or front sight base (see "A Tale of Two Carbines") and while some of the suggestions below will still apply, there are some other issues to consider when doing so.  Keep an eye out for a future article on this subject.

There are 4 options I would consider when choosing a 7.0 length free-float railed forend, and one "also ran" that is listed at the end.  Below is a comparison chart of the various rails listed showing measurements, weights, and prices.

link to more extensive chart

Daniel Defense Omega 7.0
This is a two-piece rail system that utilizes the stock barrel nut on your rifle and does not require the removal of the front sight base, delta ring, barrel, nut, etc.  It has an integral QD pushbutton sling swivel with rotation limit on the rear port and starboard side of the rail.  It is 2.43" tall (like all Daniel Defense rails) and 1.90" wide with an internal diameter of 1.10".  It weighs 7.75 oz, but for comparison purposes to other rails that have their own barrel nut you have to add back in 2.5 oz for the stock handguard cap, delta ring, and barrel nut bringing the relative weight to 10.25 oz.  The top rail is at the same height as the flat top upper and extends back over the delta ring to make a continuous rail with the upper receiver.  It's also available in a "flat dark earth" finish.

The advantage of this rail system is in the installation.  If you don't want to, or can't, or aren't allowed to remove your barrel or front sight base, this rail still allows you to have a free float system.  Examples of this may include a lack of skills, tools, or confidence, administrative rules on a department or agency owned firearm, or a barrel with a permanently attached muzzle device that prevents the removal of the front sight base.  There are other manufacturers out there that do similar but they all weigh more than the Omega.

The limitation of this rail system is that it's a two-piece (more joints means more failure points, it's just a fact of life), it's the heaviest of the Daniel Defense rails (but still lighter than a Larue, even with the 2.5 oz adjustment).  The internal diameter is also one of the smallest on the market which, on a typical 7.0 application where the front sight base remains is not much of an issue, but buyers should still be aware of it.

Daniel Defense Omega 7.0

Daniel Defense M4 Rail 7.0
This is a one-piece rail system that comes with it's own barrel nut attachment such that the stock handguard cap, delta ring, and barrel nut are discarded and installation requires the removal of the barrel in order to remove these parts.  It does not have any provision for sling attachment an as such if the user wants to attach a sling to the rail you have to add one (Daniel Defense makes several).  It is the typical Daniel Defense 2.43" tall, is slightly wider than the Omega at 1.94" but has an internal diameter of 1.45".  It weighs in at 8.5 oz, but the pushbutton sling swivel adds one oz if you choose to use it.  This rail system is almost a direct 1:1 for weight replacement when it replaces a stock set of double-heat-shield M4 handguards, barrel nut, delta ring, handguard cap, and sling swivel.  The top rail is at the same height as the flat top upper but does not extend back to make a continuous rail.  The threaded portion at the rear of the rail is attached to the rail itself via 4 spot welds.  Like the Omega, it is available in a "flat dark earth" variant.

The advantage of this system is the light weight and the one-piece construction (alright, it's really multiple pieces, but the rail itself is made up of only one).  The fact that it is a 1:1 weight replacement for stock parts is a very nice feature.  It also has the largest internal diameter of any of the 4 listed here.  Again, this may not be an issue for your application.

The limitations of this rail system include no sling-mount and the lack of a continuous top rail.  Some also consider the lack of a locking handguard/barrel nut at the rear to be a liability and cite the possibility that torque on the rail could loosen the barrel (although I've never seen it happen personally).  Others point to the spot welds at the rear as being potentially weaker than other attachment methods and/or think they are "ugly" (obviously a very subjective matter, and frankly entirely pointless).

Daniel Defense M4 7.0

Daniel Defense AR 15 Lite Rail 7.0
This is a one-piece rail system that comes with it's own barrel nut attachment such that the stock handguard cap, delta ring, and barrel nut are discarded and installation requires the removal of the barrel in order to remove these parts.  Again, this rail is 2.43" tall like the other Daniel Defense offerings, but is 2.06" wide with a 1.23" internal diameter.  This makes it the "fattest" of all 4 rail systems but it has an internal diameter second only to the M4 rail.  It also weighs in at 8.5 oz with an added one oz for a bolt-on sling attachment if you desire it.  The top rail is at the same height as the flat top upper and extends back to make a continuous rail.  The bolt-up portion at the rear of the rail is attached to the rail itself via welds.

The advantages of this rail include the light weight of the M4, the continuous rail of the Omega, plus a locking ring mounting method that prevents the possibility of torquing the barrel loose.

The limitations of this system used to be the higher price, but according to the Daniel Defense website it now goes for the same price as the M4 rail.  Be careful when shopping, however, as some retailers are still listing it at $50 more than the M4 rail.  Again, some may point to the welded construction as a negative but that is theoretical at best.  Also, the lack of a sling swivel is viewed by some as a negative.

Daniel Defense Lite Rail 7.0

LaRue Tactical 7.0" Handguard LT15-7
This is a one-piece rail system that comes with it's own barrel nut attachment such that the stock handguard cap, delta ring, and barrel nut are discarded and installation requires the removal of the barrel in order to remove these parts.  The Larue rail is 2.22" tall, 2.00" wide, and has an internal diameter of 1.20".  It weighs in at 11.87 oz making it the heaviest of the 4 rail systems here.  It includes a QD pushbutton sling swivel at the rear port and starboard sides of the rail, and this swivel does have the built-in rotation limit.  The top rail is at the same height as the flat top upper but does not extend back to make a continuous rail.  The threaded portion at the rear of the rail is attached to the rail itself via "glue", but be aware that calling the attachment method "glue" or "epoxy" disregards and downplays the strength of the attachment.  The mounting method also includes a rotation-limiting system to keep the rail and barrel nut from turning.

The advantages of this rail system include the integral sling swivels, the locking mounting system, and the short overall height.  The height is made up at the bottom of the rail which allows the shooter to get their grip higher and closer to the barrel itself.  It is also the least expensive of the 4 rails listed here.

The main limitation is the weight.  Also, the small internal diameter may be an issue for some.  The "epoxy" attachment method between nut and rail also has it's detractors just like the Daniel Defense welds have their detractors.

Larue Tactical 7.0 LT15-7

Summary
To sum up:
I would choose the DD Omega if I was not allowed to, or was unable to, remove the stock parts required for installation of the other rails.
I would choose the DD M4 rail if weight, simplicity, width, and internal diameter were critical for me.
I would choose the DD Lite rail if weight and a continuous top rail were critical for me.
I would choose the LT rail if price, overall height and an integral sling swivel were critical for me.

Also Ran...
Calling the JP Rifles Viking Tactics free-float tube an "also ran" is a bit of an insult.  It alludes to it being a lower-quality part or a less practical system, neither of which is the case.  I refer to it as an "also ran" because it's not, strictly speaking, a free-float rail system in the same vein as the others above.  It is a free-float handguard, and it does have the ability to attach rails, but it is not the traditional 4-rail system that most of us have come to be familiar with.

This is a one-piece rail system that comes with it's own barrel nut attachment such that the stock handguard cap, delta ring, and barrel nut are discarded and installation requires the removal of the barrel in order to remove these parts.  It has a 2.00" external diameter and a 1.75" internal diameter, and weighs 10.5 oz.  Since it is round, the height and width without rails is the same.  Which brings us to the rails.  The JP Vtac tube has slots milled at 12:00, 1:30, 3:00 etc. around the rail.  The slots allow the attachment of a piece of rail with the length determined by the end-user.  They can be had in 2" sections, 4" sections, or a full-length section for attachment to the top rail.  Attaching the top rail brings the height even to that of the flat top upper such that various back up iron sights or optics can be mounted.  If one wishes to mount only a front sight and otherwise keep the tube clean, there is also a piece of rail for that.  Finally, there is a sling stud attachment which can be placed anywhere the user would like for a customized sling position or for mounting a bi-pod to the bottom of the rail.

The advantages of this system are that it is completely user-configurable such that rails and sling swivels can be placed wherever required, and only where required.  It is also extremely inexpensive with the basic rail system selling for $100+/- less than the others listed here.  Of course, the price starts to climb as you add rails, and depending on how many you add it can quickly more than double the cost of the system as a whole.

The main limitation is, again, weight.  The basic tube with no rails is lighter only than the Larue above, and once rails and swivels are added it quickly becomes the heaviest option.  In addition, since the rails are added by screw mount this becomes another potential failure point.

JP/VTac Modular Hand Guard for Carbine Length Gas System on M15 Rifle

JP/Vtac rails for attachment to the main tube