AR-15 upper

[gerritm]

I want to change my upper on my DPMS AR-15 with a carry handle to a flat top style. Anything hard about this other than buying a complete upper. Any special tools needed or advice. Anyone have a flat top upper they want to part with?

gerritm

 

[chubbyzook]

If your ok with tools you can buy a stripped flatop reciver and only spend 100 bucks or so

 

[Wandering Scot]

I picked up a Wilson stripped upper for $109.00 from Brownells a week or so ago. They alos have DPMS and other brands in stock and as it is an upper you don't need to go through an FFL.
The hardest part will be the barrel nut and just make sure to check your head spacing.

 

[gerritm]

I bought a complete one from DPMS with 3 rails. I figured that was the easiest and spoke by e-mail to a customer service tech who gave me the info on what tools I needed and the basics. Hats off to their CS actually responding to an e-mail. I was impressed. I am going to swap my barrel and probably sell the old upper. Has about 500 rounds thru it with a fixed carry handle. What is the head spacing exactly. I am pretty good with tools and basic gunsmithing, but this is the first time I will take my AR apart. I have found a couple of instructional videos on AR15.com.

 

[codygjohnson]

Unless you're putting in a new bolt or barrel, headspacing won't change on an AR. The bolt locks into the barrel extension which will not change, no matter where it is in the upper. The upper swap is very simple if you have the correct tools.

 

[codygjohnson]

You will need the following tools:

Vise
AR 15 Upper Vise Block
AR 15 Barrel Nut Wrench
1/2” Torque Wrench
5/64” Roll Pin Punch
Hammer
Small Channel Lock Pliers

1. Separate the Upper from the lower.
2. Remove the Charging Handle and Bolt/Carrier Group.
3. Remove the Handguards.
4. Place the Upper in the Vise Block.
5. Place the Vise Block in the Vise and tighten snug. It’s plastic, so don’t overtighten it.
6. Remove the Gas Tube Roll Pin using the 5/64” Roll Pin Punch and Hammer.
7. Remove the Gas Tube by pushing it towards the Upper Receiver. If it is too tight to move by hand (usually is), Use the Channel Lock Pliers to clamp the Gas Tube and tap it out using a Hammer. *Don’t be a gorilla with the pliers, use enough force to grab the tube, but don’t crush it. It is very hard to crush a gas tube, but it is possible. You will mar the tube slightly, but I’ve never had one I couldn’t buff back out with steel wool, it’s under the handguards anyway...
8. Once the Gas Tube clears the gas block, remove it by pulling it back out away from the Upper Receiver.
9. Place the Barrel Nut Wrench on the Barrel Nut and loosen it by turning it counterclockwise and remove it from the Upper Receiver.
10. Remove the Barrel by pulling it away from the Upper Receiver. You may need to use some force to remove it, but it will come out.
11. Remove the Upper Receiver from the Vise Block.
12. If you are using a Stripped Upper Receiver (if not, skip to 15), Remove the Dust Cover Hinge Pin, Spring and Dust Cover. Note the placement on the old Upper Receiver before removal and replace it in the same manner on the new Upper Receiver. If you can’t do this, look it up online, I’m not going to explain how to do it.
13. Using the 5/64” Roll Pin Punch, remove the pin from the forward assist.
14. Remove the Forward Assist and Spring and Replace them into the new Upper Receiver. You will need to apply a small bit of pressure to the Forward Assist button when installing it to give clearance for the pin to slide in.
15. Clean All of your parts well before reassembly.
16. Place the new Upper Receiver in the Vise Block and Place it in the Vise.
17. If you have some Anti Seize Lubricant, use it on the Barrel section that slides into the Upper Receiver. This will aid in assembly and disassembly later.
18. Insert the Barrel into the Upper Receiver making sure that the indexing pin located on the top of the barrel is in the channel on the top of the Upper Receiver’s threaded portion.
19. Replace the Barrel Nut and hand tighten it onto the Upper Receiver.
20. Place the Barrel Nut Wrench on the Barrel Nut and Place the Torque Wrench on the Barrel Nut Wrench. Torque the Barrel Nut to 30 ft/lbs. I like to loosen and tighten the Barrel Nut 3 times to help fully seat the Barrel in the Upper Receiver.
21. Place the Gas Tube into the 12 o’clock hole in the Barrel Nut and push it into the Upper Receiver. It probably won’t slide right in, this is normal.
22. Remove the Gas Tube and tighten, do NOT loosen, the Barrel Nut bit by bit until the gas tube slides into the upper receiver freely. The Barrel Nut needs at least 30 ft/lbs, but it can go tighter to get the Gas Tube into the Upper Receiver. Make sure the tube inserts straight and not cocked to one side.
23. Insert the Gas Tube into the Gas Block opposite of how you removed it. If you look through the Gas Block Roll Pin hole, you can see when the Gas Tube is inserted far enough in.
24. Tap the Gas Tube Roll Pin back into place.
25. Remove the Upper Receiver from the Vise Block.
26. Replace the Handguards.
27. Replace the Charging Handle and Bolt/Carrier Group.
28. Replace the Upper Receiver onto the Lower Receiver.
29. Test fire and zero the rifle and you’re done.

This is all assuming you have standard (non free-float) handguards. Let me know if you don’t, I can modify directions for free-float if necessary. This is a good time to upgrade to them...

 

[gerritm]

Great instructions, thanks. One question, the barrel has the A style front sight. Do you just drive the pins out to remove it? I won't need it with the new optic set up.

 

[Joat]

to remove the A frame (A2 front sight) you drive the taper pins out. Notice the word "taper"? They only come out one way, look at the ends of the pins and drive from the small end towards the large end. You will have to replace it with a gas block unless you want a single shot AR.

17. If you have some Anti Seize Lubricant, use it on the Barrel section that slides into the Upper Receiver. This will aid in assembly and disassembly later.

Do not use anti-seize on the barrel nut or extension. Moly grease is the proper material to use here and on the receiver threads.

Joat

 

[codygjohnson]

You can remove the front sight by driving the two pins out of the bottom and drifiting it off of your barrel. THe barrel has a step down right in front of the sight, so it's pretty easy to get off once you get it started. Drift it with a brass drift or if you don't have one, use a block of wood or something else soft, yet sturdy. If you don't really care obout damaging the sight, just wack it with a hammer. Keep in mind that it is also the gas block, so if you want to get rid of the sight, you will need a stand alone gas block.

 

[AusTex]

Yes drive the pins out.. sometimes they come right out sometimes not. Once you get them out id spray some lube on the barrel and slide the post off the barrel. Some have tight fits and you can scratch your barrel when taking it off.

Do not throw the a front sight block away or get rid of the pins.

As the front site is driller on that barrel and that barrel only. Just in case you decide to switch back or sell the barrel at a later date.

 

[codygjohnson]

Do not use anti-seize on the barrel nut or extension. Moly grease is the proper material to use here and on the receiver threads.Joat

The upper receiver is aluminum, the barrel is steel, a galvanic reaction is inevitable. Prevention from galvanic reaction is one of the uses of zinc anti-seize.

 

[Joat]

As is the use of the moly grease

 

[cconn]

Assemble your own LOWER, UPPER, FREE FLOAT, TRIGGER, GAS BLOCK - Step by step instructions! - AR15.COM

Excellent guide to assemble an AR.

 

[gerritm]

I decided to cheat, thanks all for the help. I bought a DPMS pre assembled upper from CTD. It seemed like a simple solution. Now I will sell the upper complete.

ARR-521 - AR-15 DPMS .223 A3 LoRider Complete Upper Assembly 20" Bull Barrel Flattop 1 to 9" Twist with Bolt and Carrier