Noob Technical Questions

[rlandrum]

I'm having some trouble figuring out some AR-15 terms thrown around on various websites. I've googled "AR-15 terminology" but the results seem to centered around acronyms. If these are answered elsewhere, feel free to post the link and I'll happily RTFL.

What's the difference between a quad rail and a hand guard? Several Youtube videos seem to use them interchangeably, but I suspect I'm missing something.

Forward of the hand guard is a small piece where the front sight it usually mounted. Is this part of the hand guard, quad rail, or front sight?

Is the barrel detachable from the upper receiver? I am assuming they're press fit, since it seems they're rarely sold separately, and seemingly always include a hand guard or quad rail.

Thanks!

[elkbow]

Welcome to the forums...

Ok, handguard or also called forearm, can get had in many configurations. A quad rail means it have picatinny rails on all 4 sides, top, bottom, left and right. You can get handguards where they are smooth (round) all the way around, triangular, etc. You can add picatinny rails to them in different sizes on the sides or bottom to add accessories like lights, etc.

The small piece forward of the handguard, if there is no front sight, is a gas block. The front sight on a normal AR also is a gas block inside of it. There is a hole drilled in the barrel so when you shoot the gases go up through the hole, in to the gas block, and there is a gas tube running back to the upper receiver and it slides inside the gas carrier key on the bolt carrier and the gases push the carrier back when fired there by ejecting the fired case and since there is a spring in the stock it pushes the carrier and bolt back forward and loads the next round out of the magazine.

The barrel is not press fit, but it does have an extension on it with a pin that slides in to the upper receiver only one way. Then there is a barrel nut that holds it in place. The barrel nut usually comes with the handguard. There are different ways the handguard mount, some screw to the outside of the barrel nut, others clamp on, etc. So realistically you can swap barrels, but not that easy of a task as the handguards are tough to remove as well as the barrel nut, so you don't want to be switching barrels very often unless you want to completely change your upper over to a different caliber, in which case you would need a barrel and a bolt that is configured for that caliber and headspaced to the barrel.

[OC455]

http://www.brownells.com/.aspx/lid=11004/learn/

If you check these videos through, it gives you a basic understanding on how the AR rifle is constructed and the terminologies used for the basic platform. As explained by elkbow, the other phrases you heard or have seen all refer to similar items in different configurations (quad rail, free float forend, free float tube....etc, etc)

[thevolkp]

Good info. From another Noob.

[SAMPSON]

I watched that entire series, sometimes more than once, and I still dont know it all, but those brownells videos are a good education. dont hesitate to aske questions if you dont quite get something there are a lot of helpfull individuals on here.

[buddy]

http://www.brownells.com/.aspx/lid=11004/learn/

If you check these videos through, it gives you a basic understanding on how the AR rifle is constructed and the terminologies used for the basic platform. As explained by elkbow, the other phrases you heard or have seen all refer to similar items in different configurations (quad rail, free float forend, free float tube....etc, etc)

These are very informative videos even for those of use that thought we knew everything. Thanks

[shrxfn]

Also the building your own AR sticky topics at AR15.com are very good as well. They are what I used when building my lower for my AR but I am more of a reader than a watcher.

[rlandrum]

Thanks for all the excellent info. The videos are super, and I'm working my way through them.