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1/14/2017 8:11:35 PM
Posted: 2/13/2009 8:30:04 PM EST
[Last Edit: 2/17/2009 11:39:43 AM EST by ru4freedom]
I couldn't find a Free Float Tube that would work with the Gas Piston Kit I was putiing on my Coyote Killer...., so I configulatated my own using the barrel nut from am old DPMS Float Tube & a piece of 6061-T6 Aluminum Tubing I got off of eBay!

Float Tube Chronicles: http://flickr.com/photos/shanepics/






Link Posted: 2/13/2009 8:38:04 PM EST
Nice!
Link Posted: 2/13/2009 11:08:36 PM EST
please go into more detail; finish, OD of barrel nut; inside diameter of tubing; how you actually secured the float tube to the barrel nut; vendor on ebay you got the tubing from etc. I like it; and it may be a solution for my rifle. thanks. BTW I looked at your link and it just brought up more questions.

Link Posted: 2/14/2009 11:14:33 AM EST
[Last Edit: 2/15/2009 6:18:52 PM EST by ru4freedom]
Originally Posted By Enforcer:
please go into more detail; finish, OD of barrel nut; inside diameter of tubing; how you actually secured the float tube to the barrel nut; vendor on ebay you got the tubing from etc. I like it; and it may be a solution for my rifle. thanks. BTW I looked at your link and it just brought up more questions.



http://flickr.com/photos/shanepics/

Where to begin?? Well I wanted to build a Optic Dedicated Coyote Killer!! And since that is the AR I shoot (and clean) the most at the range & in the field..., I wanted it to be Piston Driven!!

I have had very good results with the TNW Gas Piston Kits on M4's, but this is the first time trying one on a potential "Tack Driver" & with my experience to get em' to "drive tacks" They gotta be floaters!!

So I had a 16" DPMS Bull Barrel turned down to .750" & went in search of a Free Float Tube. Well..., I couldn't find one that would work so after taking some measurements I decided I could probably just make my own using a DPMS Barrel Nut, some 6061-T6 Aluminum tubing off eBay & some 8-32 Button Head Screws! The Tube OD is 2.25" ID is 2.078 & clears the TNW unit by about .015"

The only real challenge was recessing the push rod hole in the barrel nut to compensate for the extra .75” in length as compared to a standard Barrel Nut/Delta Ring which is what the TNW Piston Kit is designed to be used with.

After first installing the barrel & DPMS barrel nut & test firing using a standard DI gas tube to make sure the Barrel nut was indexed properly I disassembled & drilled out the appropriate hole 3/8” recessing to a depth of .75” for the push rod spring to seat against.

As far as the vents go.., the only thing I had to work with to create vents was a variety of drill bits. As shown in the pictures I sealed up the holes in the rear of the barrel nut to block gas from blowing back in my face, so I decided to locate some gas vents close to the piston & direct the spent gas to the sides & forward of the Scope & this was the vent hole pattern I ended up with....., good, bad or ugly, it works really well!!

The finish is good old "Rust-Oleum" Industrial Enamel #7578....., Now don't laugh!! The finish is actually tough as nails & it matches my DPMS Upper & Stag Lower perfectly and at a cost of only $5 a can ya' gotta love it!!
I baked it on @ 200 degrees for 60 minutes to speed up drying time!

The idea of attaching the tube to the outside of the barrel nut came from the White Oak Amorment Float Tube that I was originally going to use...., but as it turned out WOA's barrel nut design would not have enough clearance for the TNW Pushrod Spring! I used 8-32 Button Head Torx Drive screws 2 per side & 2 on the bottom. I don't really care for the looks of the exposed screws...., but it's absolutely rock solid! The sling stud is kinda' fugly too but a sling is a must for packing the AR into my Coyote hunting areas!

All & all I'm pretty happy with the way it turned out, It's only .25" larger OD than a standard Float Tube & weighs less than 3 ounces more!

Materials & Tools Used

DPMS Barrel Nut OD 2.0"
6061-T6 Tubing 2.25" OD & 2" ID .125" wall thickness! –––––– eBay vendor: discount_steel
6 - 8/32 Button Head Torx Drive Screws
1 - 8/32 Tap
2 - 10/32 Sling Studs (1-Bipod & 1-Sling)
1 - 10/32 Tap
Drill Press
Tap Handle
Hack Saw
Bench Grinder
Bastard File
Sand Paper 80, 120, 320, & 600 Grits
Rust-Oleum Pro. HP Enamel #7578 Flat Black

My first Accuracy test shows fairly good accuracy, sub MOA @ 100 yds. with S&B 55 gr. FMJ ....., but I know I can cut that group in half with hand loads!!

More accuracy tests to come!!
Link Posted: 2/14/2009 11:36:55 AM EST
That doesn't look bad at all. Nice work.
Link Posted: 2/14/2009 12:49:28 PM EST
[Last Edit: 2/15/2009 6:20:20 PM EST by ru4freedom]
Thanks Guys....., I'm really not all that handy with tools! There was a lot of things that could have gone wrong but luckily didn't!

I guess "Murphy's Law" must have been taking the day off!!
Link Posted: 2/15/2009 9:16:50 AM EST
thanks for the additional information. I am going to explore this a little further. I have the DPMS LoPro classic and the large gas block really limits what you can do. I either need to replace the gas block and buy a regular free float tube or attempt this modification. yours really turned out well.

Good job!
Link Posted: 2/15/2009 9:27:35 AM EST
Nice work!

Needs more crop circle holes.

Always nice to see someone take the initiative and make something work for them.

Link Posted: 2/15/2009 9:50:52 AM EST
Looks good!!
Link Posted: 2/15/2009 12:09:09 PM EST
Very nice work !

It's great to see people with such skills !
Link Posted: 2/15/2009 12:11:27 PM EST
[Last Edit: 2/15/2009 12:31:22 PM EST by ru4freedom]
Originally Posted By Enforcer:
thanks for the additional information. I am going to explore this a little further. I have the DPMS LoPro classic and the large gas block really limits what you can do. I either need to replace the gas block and buy a regular free float tube or attempt this modification. yours really turned out well.

Good job!



Your DPMS Gas Block should come off easy enough with 2 set screws. Could you just remove GB, install a regular Float Tube assembly & then reinstall the GB? The forward end of the Float Tube will generally fall just short of the GB when installed.

Link Posted: 2/15/2009 12:18:53 PM EST
[Last Edit: 2/15/2009 7:48:32 PM EST by ru4freedom]
Originally Posted By GhostRing:
Nice work!

Needs more crop circle holes.

Always nice to see someone take the initiative and make something work for them.



Thanks GhostRing!! That's what I'll name my funky little vent design "Crop Circles" ......, or hey., maybe even "Ghost Rings"

Actually the Desert areas I hunt can get pretty dusty at times with blowing sand & stuff so I decided to go with a minimal amount of "Crop Circles" to vent out the spent gas & hopefully not allow much sand in!

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Link Posted: 2/15/2009 1:22:09 PM EST
very cool!
Link Posted: 2/15/2009 2:23:32 PM EST
I like it!
Link Posted: 2/15/2009 2:53:42 PM EST
Very impressive! Good job man.
Link Posted: 2/15/2009 2:55:25 PM EST
Nice work man! Good old American ingenuity!
Link Posted: 2/15/2009 3:38:06 PM EST
Originally Posted By Shung:
Very nice work !

It's great to see people with such skills !



+1
Link Posted: 2/15/2009 4:04:48 PM EST
That is damn nice looking. Good job.
Link Posted: 2/15/2009 4:04:54 PM EST
Tag for tomorrow! This looks awesome.
Link Posted: 2/15/2009 4:26:08 PM EST
it looks great!
Link Posted: 2/17/2009 11:31:50 PM EST
[Last Edit: 2/17/2009 11:32:47 PM EST by ru4freedom]
Thanks for the good words guys!

I decided to build up a different Lower receiver for this rifle......., I'm thinking the "Skull & Crossbones" receiver will be a little more appropriate for a dedicated Coyote killin' rig!!
Link Posted: 2/17/2009 11:45:47 PM EST
Would look neat to do one like the 50bmg's barrel shroud.

Will
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