If you are at all familiar with the AR-15 quad rail market, you are probably familiar with the two main styles of quad rail handguard - drop-in and free float. If you are not familiar, you can refer to our handy guide discussing the pros and cons of each.
Now allow me to throw another option into the mix - the Carbine Length AR-15 Drop-in Quad Rail with Forward Extension. Sometimes referred to as the Extended Carbine Length Drop-in Quad Rail or the Carbine Length Drop-in Quad Rail with A2 FSP Cutout, this rail is designed to combine many of the benefits of the drop-in and free float rails.
More rail space than the standard carbine length drop-in rail.
Unlike the standard drop-in quad rail which extends only to the rear of the A2 front sight post, the quad rail with forward extension extends several inches beyond the A2 front sight post. It has a cutout on top for the front sight post and on the bottom for the sling and bayonet attachments. Everything installs in place around the front sight without any gunsmithing involved.
This gives you a bit more flexibility in accessory placement or hand placement You can attach your flashlights or bipods up front and still have room to handle your rifle at the near end of the rail.
Easier to install than an extended free float rail
The installation of an extended free float handguard on a carbine length AR-15 can be a hairy process. It involves removal of the A2 front sight/gas block assembly and installation of a low profile gas block. You will also need to remove the delta ring. It requires some gunsmithing tools and a little bit of expertise in order to install it. For most of us, this means taking it to your local gunsmith to have it installed for you.
The drop-in rail, on the other hand, simply drops into place around the front sight post and is held together with a few set screws. Installation only takes about 5 minutes. It requires absolutely no expertise and no special tooling whatsoever.
Retain use of the A2 front sight post
Another advantage of the extended drop-in quad rail over the free flaot is that it leaves the A2 front sight post intact, allowing you to use it as a front sight. With a free float setup, you would need to purchase an install some type of rail mounted front sight if you wanted to use some type of iron sight system.
Heavier than the standard drop-in or free float setups
On the down side, the extended drop-in rail is obviously a bit heavier than the traditional drop-in rail. It weighs about 18 ounces, which is about 50% heavier than the regular carbine length rail. It is likewise heavier than the free float setup, as you have the added weight of the rail in addition to the extra weight from the front sight post and the delta ring.
Not ideal for long distance or competitive shooting
Also, for long distance or competitive shooting, you are not going to get the same level of accuracy as you would with a free float rail. For most shooters, using their AR for home defense or tactical purposes, or for taking it to the shooting range every now and then, this impact is going to be negligible. But it is something to keep in mind if you plan on using your rifle at longer distances or in competitions.
All in all, the drop-in quad rail with forward extension offers an inexpensive and easy to install alternative for AR-15 owners who want more rail space without the added hassle of installing a free float handguard.
***Please note that this quad rail will not fit the Ruger AR-556 due to the rifle's irregular bayonet lug.***

AR-556 ® With Free-Float Handguard. Flat top upper receiver features a Picatinny rail for easy attachment of magnified optic, red dot or open sights. Made from 7075-T6 hard-coat anodized aluminum forgings, shot-peened and proof-tested 9310 steel bolt, and 8620 steel bolt carrier. The inside diameter of the carrier and gas key are chrome. Free Float Handguards. GunTec AR-15 Freefloat Handguard 15' M-LOK Aluminum Black GT-15MLK. GunTec AR-15 Freefloat Handguard 15' M-LOK Aluminu. Leapers UTG PRO AR-15 Carbine Length Drop In Quad Rail Aluminum Black MTU001T.

Intro

Most military configured barrel assemblies come with the Barrel Nut, Handguard Cap, and front sight base installed. We will demonstrate how to assemble the delta ring assembly, the handguards and the flash hider. If you’re going to install a free float handguard then you can skip the standard barrel segments and watch the segments on installing a free float barrel. You may, however, depending on your barrel’s configuration need to watch the segment on installation of flash hiders. Here again it is important to follow the order of the steps as we present them. This will eliminate rework and allow you to align components with previously installed parts. You should have your parts organized on your bench. You’ll need a good bench vise, the upper receiver vise block and insert, a barrel wrench, a torque wrench, the taper pin starter punch, number 2 & 4 roll pin holders and punches, a 4 oz. pall peen hammer, and the front sight bench block.

Installing Delta Ring and Barrel Into Upper Receiver Mil-Spec

Ar 556 Free Float Handguard

To install the barrel and handguard slip ring assembly and gas tube you’ll need the upper receiver vise block with the insert, a barrel wrench, a torque wrench, snap ring pliers, and a number 2 roll pin holder and punch. A small flashlight would be handy also. The methods for installing a mil spec barrel are the same for all barrel lengths.

Ruger Ar 556 Rails

1. From the rear of barrel, slide the handguard slip ring with the narrow end facing forward, the
2. Use your snap ring pliers to expand the handguard retainer ring and seat it into place in the cut on the barrel nut.
3. Place your upper receiver into the upper receiver vise blocks and install the insert into the back of the receiver. Put the entire grouping into your vise jaws up to the lips on the side of the vise blocks and tighten down your vise until you have a firm grip on the blocks.
4. Next slide your barrel into the front of the receiver making sure you align the pin on top of the barrel with the cut in the upper receiver threads.
5. Take your barrel wrench and attach it to your torque wrench which is set to 30 foot pounds. Pushing against the slip ring assembly tighten the barrel nut down to 30 lbs. 30 foot pounds of torque is the minimum amount needed to secure the barrel. We’ve typically found that you will achieve better accuracy with a minimal amount of torque above 30 ft. lbs. Make sure the cuts in the handguard retainer ring and spring are on top of the barrel. Look down the top of the barrel into the cuts of the barrel nut and into the receiver. It may
be helpful to remove the vise block insert from the receiver and shine a flash light from the back of the receiver. You’re looking for one of the cuts in the barrel nut to align with the gas tube port on the front of the receiver. Typically this doesn’t happen with your first turn.
6. Note the distance that you’ll have to turn the nut to align with the next cut on the barrel nut and increase the torque setting on your wrench to 40 lbs.
7. Replace your insert back into the receiver if you’ve taken it out.
8. Tighten the barrel nut a bit more; it is always better to do this in small steps so that you don’t go past the next cut you’re trying to align. Check the alignment again. Keep repeating these steps and increase the torque setting on your wrench until you get visual alignment.
9. Once you have visual alignment, place your gas tube with the bend upward and the bulge
towards the rear through the barrel nut into the receiver. It should pass through without any binding or resistance. If you encounter any resistance, remove your gas tube and turn the barrel nut either on or off to fine tune the alignment. A handy tool that prevents damage to the gas tube is to use the barrel nut alignment rod instead.
10. Once you’ve achieved proper alignment, you can install the gas tube into the front sight base.
11. Remove your barreled receiver from the vise block and place it into the front sight base block
with the words PINS IN facing up. Align the gas tube with the roll pin hole in the front

Install A Free Float Rail Ar556