Monday, April 29, 2013

Basic AR-15 Modifications-Gas Block Installation

In our last blog entry, we gave instructions on how simple it is to switch out two-piece handguards. This time, we will give basic instructions and tips on how to remove a front sight base and install a gas block of a different type. The ability to remove the front sight base is necessary if you want to install most free float handguards as well.  As we stated in the previous blog, make sure you are aware how any modifications you perform on your rifle may affect its warranty, and keep safety in mind at all times.  If you are unsure if your weapon is safe to use, have it inspected by a professional gunsmith.

There are a few very necessary tools and parts required for this modification.  A set of punches (roll pin and standard), a hammer, a crescent wrench for the flash hider, and a special front sight base bench block will make this task easy and successful.

Removing the gas tube roll pin
1.  The first step will be to knock out the gas tube roll pin with a small punch.  If you have two piece handguards, you will need to remove them to access the gas tube.  Once the roll pin is removed, pull the gas tube toward the upper receiver and it should slide out of the front sight base.  When it is removed, you can gently bend it enough to then pull it forward out of the upper receiver.  If you carefully do these two tasks, you should be able to reuse the roll pin and gas tube (now is a perfect opportunity to use a pipe cleaner to clean the inside of the gas tube, too).  You will also need to remove the muzzle device (flash hider, etc...) so that the front sight base can be slid off the barrel toward the muzzle once the taper pins are removed in the next step.

Using a punch to drive out the taper pins
2.  At DTI, we install front sight bases with taper pins and they will need to be driven out of the front sight base from the smaller side of the pin.  The smaller diameter of the taper pin is found on the left side of the weapon, opposite of the ejection port cover.  This is where the front sight base bench block comes in handy.  This "jig" will carefully hold the front sight base steady and allow you to begin to drive the pins out with a larger punch.  Make sure the upper is on a surface level with the bench block jig and that it is wrapped in a rag or something soft to prevent marring when the pins are driven out. The pins can be tight, but once they get moving a smaller punch can finish driving them out of the front sight base.  Now you should be able to gently tap the front sight base with a hammer to remove it off of the barrel towards the muzzle.

Front sight base with taper pins removed
3.  Now, install the gas tube into the new gas block by correctly inserting it, making sure to have the roll pin hole aligned so that the roll pin can be driven through using a roll pin punch and finished with a standard punch.  Once this is accomplished the gas block is ready to be mounted on the barrel, and the attached tube inserted back into the upper receiver. 
The taper pins from the original front sight base will leave two crescent shaped marks on the bottom of the barrel, so if you do not want this visible it is important to select a gas block that will cover these marks (something larger than a low profile style, usually). 
It is very important to make sure the gas port of the gas block is centered over the gas port of the barrel. This can be done by sighting down the barrel from the end of the upper receiver, and if you use handguards that do not require an endcap, make sure that you leave a thin space (the thickness of the endcap), and do not mount the gas block all the way back to where the barrel profile thickens.

YHM Specter gas block installed

4.  If your gas block uses set screws or is a clamp on style with tightening screws/bolts, a little loc-tite should be applied once the gas block is mounted and you are sure the weapon is operational.  If it is a clamp-on style with a number of screws, make sure that they are all tightened evenly and that any gaps between the two pieces of the gas block are equal.

Thanks for reading our blog.  In upcoming blog entries we will continue to offer instructions on basic AR-15 modifications, so stay tuned.  If you have any questions about gas blocks and what will work with your set-up, the parts we sell, or the rifles we manufacture at, please feel free to contact us.

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