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Posted: 7/13/2004 5:46:33 PM EDT

How do I remove the barrel from my upper. I got the hand guards off. Do I need any special tools? I want to replace my 20" with an M4 barrel. One I do get it off what should I do for putting it on? Do I need to head space it or anything of that nature?

Link Posted: 7/13/2004 5:59:05 PM EDT
yup, you need special tools. you should get the military armorers book, at least, so you know what to get. Realistically, you should have an upper clamp and a barrel nut wrench. available from most manufacturers. You might have to remove the front sight, depending on the handguard you end up using, and you'll need a roll pin punch to remove the gas tube.

Link Posted: 7/13/2004 6:00:04 PM EDT
headspacing is determined by the bolt and barrel extension, neither or which you mess with. So you should be ok there.

Link Posted: 7/14/2004 4:39:40 AM EDT
Thanks guys. I think I can pull this one off as soon as I get the tools. Thanks for the advice.

Link Posted: 7/14/2004 2:14:14 PM EDT
[Last Edit: 7/14/2004 2:16:29 PM EDT by A_Free_Man]
Use an action block, NOT barrel vise jaws. You don't need a torque wrench, but do need the armorer's wrench ( barrel wrench).

First, remove the handguards.

Tap out the small pin that holds the gas tube into the front sight base, remove the gas tube.

Place the upper receiver in the action block, and made sure you use the insert that slips inside the receiver.

Use a 1/2" breaker bar with the armorer's wrench to loosen the barrel nut, spin it off, pull out the barrel.

Put a dab of WHEEL BEARING GREASE (not NEVERSIEZE) on the threads of the receiver, and spread it around. A little on the inside of the barrel nut, too. I like to put some grease inside the receiver where the barrel extension will plug in.

Plug the new barrel into the upper receiver. Spin the nut up. Now, you have screwed stuff together. You can feel when something is loose, and when it is tight.

(IF YOU MUST use a torque wrench, bring it up to 30 ft-lb, which is the minimum recommended. Then remove the torque wrench, and replace with breaker bar for the rest of this. You don't need to know what the torque is for alignment, just the minimum. What it is after this, it is.)

Snug it up until it feels tight, and continue on to align the notch with the gas tube hole. You can use a drill bit shank the same size as the gas tube to check. You will have to get the weld spring and snap ring all lined up, too. Continue nudging the barrel nut until the drill bit shank can be inserted and has an equal amount of play to each side. You are done.

Wipe away excess grease. Wipe down the barrel with oily cloth.

Now replace the gas tube, gas tube pin, and handguards.

You are done.
Link Posted: 7/14/2004 7:24:03 PM EDT
Thanks for the info man, the help was great

Link Posted: 7/14/2004 8:05:39 PM EDT
Excellent post, Free_man. The last half will help me a lot, as I have all the parts for my first AR upper sans barrel and handguards.
Link Posted: 7/16/2004 6:17:58 AM EDT
It really is this easy.

Action block vs barrel vise jaws:

Barrel vise jaws, the torque gets applied to the little hard steel indexing pin and soft aluminum of the notch in the receiver. Visualize: Barrel is clamped in jaws in vise, wrench twists barrel nut, nut twists the receiver, and what keeps the receiver from turning? That pin and notch. This is how canted front sights happen.

Action block, the receiver is held stationary by the action block in the vise. The torque of the barrel nut is directly against the receiver, which is held by the action block. The only twisting force on the barrel is from friction between the barrel nut and front of the barrel. You did apply a little grease, didn't you?

You still need to own barrel vise jaws. When you remove and replace compensators and flash hiders if you were to place the receiver in an action block, and twist on the muzzle device on the end of the barrel, the torque is concentrated on that indexing pin and receiver slot. For replacement of muzzle devices, use the barrel vise jaws. Always remove the gas tube first, in case the barrel slips in the jaws (likely) in which case the gas tube can be damaged. (definition of "Experience": I f-----d up like that already.)

My caution about the insert in the receiver with the action block. If this is not used, or at least a bolt carrier, the receiver can be bent in the action block, as the receiver is twisted in the block. Just use the insert and you will have no problem.

Link Posted: 8/23/2004 9:13:54 PM EDT
[Last Edit: 8/23/2004 9:22:48 PM EDT by Sharpshot]
edit: doh! I answered all my own Q's thanks to FALARAK's tacked post.
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