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9/19/2017 7:27:10 PM
Posted: 10/10/2003 8:46:35 PM EDT

I've just bought a DCM type armalite tube for my 20" upper that I use for service shoots. How do I correctly index it? Are there some sort of washers/shims needed or do I just do it as close as I can and hope that it is tight enough? I’m waiting for my receiver block and wrench to show up so I haven’t tried it yet. Thanks for any help.

Link Posted: 10/11/2003 3:19:04 PM EDT
[Last Edit: 10/11/2003 3:21:00 PM EDT by rebel_rifle]
Did it not come with instructions on installing it? If not, you need to get them as the Armalite tube is pretty easy to install and the directions are easy to understand. The Armalite tube utilizes a lock ring and you just install the tube on the modified barrel nut. You will also have to modify the front sight base and the handguards. The directions will explain this as well.
Link Posted: 10/11/2003 3:43:15 PM EDT
[Last Edit: 10/11/2003 4:12:25 PM EDT by HeadDamage]
Well I might have been had, this may not be a armalite unit. It has no lock ring, it is all one solid unit (it did come with hand guards). My best guess is that I either need some sort of indexing washer or the main tube some how unscrews from the nut but it is well attached at this time and I am reluctent to force it. Ok, I went out to the shop and forced it. The main tube is seperate from the nut and appears to be either treaded or pressed in. I think it is threaded but moves VERY stiffly. I guess I torque the nut onto the action and then use the barrel wrench to hold the nut in place while I use a strap wrench to twist the tube untill it lines up. BTW the unit is Stainless Steel. Any additional ideas or advice would be great. Thanks.
Link Posted: 10/11/2003 6:49:41 PM EDT
[Last Edit: 10/11/2003 6:54:35 PM EDT by rebel_rifle]
If it is stainless, it is definately NOT an Armalite float tube. It is also not a Rock River, DPMS, Bushmaster or CLE. The only tube I know of that is stainless is the Merchant float tube. Without knowing exactly what kind of tube it is I am at a loss in telling you how to install it. Did you buy it used? If so, see if the previous owner can tell you what one it is and then try to contact the maker and get the installation instructions. You will also more than likely have to modify the gas tube as well in order to get the handguards to fit. As I recall, if it is a Merchant tube a standard GI gas tube will work. But, most others require it to be re-bent to fit.
Link Posted: 10/14/2003 11:34:12 PM EDT
Ok, the tools showed up today and I stripped down the old unit and installed the DCM syle one. It all went together ok and the stock gas tube worked with a little bending. I'll try it out on the range asap. Thanks.
Link Posted: 10/15/2003 6:11:23 AM EDT
[Last Edit: 10/15/2003 6:11:51 AM EDT by rebel_rifle]
Here are some tips on getting the most out of your float tube: 1. Make sure the front of the float tube is not touching the rear of the front sight housing. You want at least about .020" clearance with up to .030" being acceptable. 2. Make sure the gas tube is not touching the float tube and the carrier key freely slides up on it inside the upper. Just light finger pressure on the carrier itself sliding up on the tube will do. 3. Make sure the handguards are nice and tight on the tube. Also, make sure the gas tube is not touching the inside of the handguards. If it is, take a Dremel tool and work on the inside of the handguards a bit so you can improve the clearance. 4. Once you get a true no wind zero, take some of the Wicking Loctite and apply it to the front band of the front sight housing that is around the barrel. Even with snugged screws holding it, it can come a bit loose and your windage zero can slip a bit. Later when re-barreling, a whack with a rubber mallet or a gentle application of heat will remove it.
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