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Replacing an OEM handguard with a free-float keymod rail

Posted by Zach M on

Tim writes:

I was just checking out your website and shopping for some AR-15 upgrades. I have ordered a S&W M&P15 Sport II and wanted to start upgrading it. This is my first AR and want to make sure I am ordering the right parts and wondered if you could help.

I am going to order a charging handle and ambi bolt release lever, which are both self explanatory, but I also wanted a free float rail. I was looking at this one on your website.

I assume I need a low profile gas block as well. Are they all the same? Is there anything else I will need to install the rail?

Any help you can offer would be appreciated.



Zach of TNA writes:

Hi Tim,

Congratulations on the gun purchase, great choice!

As far as compatibility, yes all the low-profile gas blocks are pretty much the same. This steel gas block is most popular although out of stock until late Feb. This aluminum one is also a popular choice.

When you remove the handguard you have to pull back the delta ring. Some folks do it by hand or with the handles of a channel-lock wrench but it can be a pain and cause lots of swearing. We offer a couple of a Delta Ring Removal Tools that can make that much easier.

To get the front sight off you have to knock out two pins that hold the sight to the barrel, and one pin that holds the gas tube in place. We offer a set of pin punches here.

The front sight may be really tight on the barrel so you can either bang with a piece of lumber or use one of our non-marring hammers.

A vice block for the upper receiver lets you hold the Upper in a vice without deforming the receiver and again reduces the cursing involved.

You'll need a barrel nut wrench to remove the factory barrel nut since your new rail comes with its own special nut. This wrench also conveniently has a 3/4" notch that you can use for removing the flash hider (a necessary part of removing the gas block).

When you install the new barrel nut it is recommended to torque between 30-80 foot pounds, and we've got a torque wrench for that. Some folks just wing it, that's up to you.

You should also get a fresh crush washer for when you re-install the flash hider.

There are lots of videos on Youtube that walk you through this process, here is one is example.

Let us know if I can assist further. Best regards,


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