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Installing the JP VTAC FFT aka "How Bibliophobia can make your life exciting!"

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Well, I finally scrounged up all the tools necessary to install my JP VTAC free-float tube, and with the weekend approaching I decided it was high time to get it together. So I went to the shop today, and there the adventure began. What follows is a how-to of sorts for those brave souls who dare attempt similar constructs.

Be sure to lock your receiver tightly into a suitable receiver jig before commencing the following steps. I use DPMS' excellent 'Claw' device.

#1. Removing the gas block.


This is a really simple task on the LR-308, as there are 2 set screws that attach the gas block/gas tube assembly to the barrel. Simply loosen the 2 screws, be sure not to lose them, and remove the gas block by pulling it down the barrel.

#2. FFT Removal.

Removing the free float tube happens in 2 parts, removing the main tube, and removing the barrel nut. To remove the main tube, simply unscrew the main tube using a strap wrench.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install7.jpg

The two parts of the FFT are now seperate, and as seen here.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install2.jpg

Removing the barrel nut will mean heating it with a heat-gun for about 7-8 minutes to soften up the Lock-tite that the factory applies to it. Be careful that you try to heat evenly around the nut, as you don't want to spot-heat it and risk messing up your receiver jig.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install10.jpg

Once it's hot, you're ready to remove the barrel nut with a suitable wrench.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install9.jpg

Don't touch it with your bare hands, it will be hot for a while. I cooled mine off with cool running water right after removal.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install12.jpg

#3. We're ready to install the VTAC!! The VTAC is composed of 3 primary parts, where the factory FFT was only 2. You have: The main FFT housing, a barrel nut, and a larger receiver nut. There are some smaller components as well but they don't play in right now. I will mention that I did not do several things that the JP manual recommends, like removing the Teflon from my receiver threads, and using lock-tite to hold the receiver nut in place. I left the Teflon on the receiver threads so that using lock-tite wouldn't be necessary.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install14.jpg

Carefully lubricate the receiver threads and thread the JP receiver nut onto the receiver.

This took quite some effort but the threads were well lubricated and I made sure I reversed directions frequently to avoid letting the threads bind.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install15.jpg

You may have noticed that at this point in the installation, my upper is NOT in the claw, but carefully wrapped and upside-down in the vise. I did this so that when I got the gas-tube hole in the receiver nut aligned with the receiver, I could use a straight rod ( properly sized ) to maintain alignment while tightening the barrel nut (next step).

#4. The barrel nut goes on quite simply. The pictures should make it self explanitory.

Apply anti-seize compound to the threads of the barrel nut.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install16.jpg

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install17.jpg

Thread the barrel nut into the receiver nut.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install18.jpg

Use a suitable wrench to tighten the barrel nut, JP recommends 35 to 80 ft/lbs of torque. My boss had run off with the torque wrench so I simply tightened it 'till my neck-hair stood up and my sphincter clinched and the voices in my head screamed "STOP!". That's perfect.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install20.jpg

As you tighten the barrel nut, be sure to watch the location of the recesses in the barrel nut, you don't want to tighten it up too much and block off the gas-tube hole with one of the small lugs, but if you do and it's getting in the way, you can grind off the offending lug with a dremel.

#5. Now that you have your barrel nut and receiver nut properly aligned and tightened, it's all very easy from here. Check your gas-tube to be sure that it goes into the receiver properly, and that nothing is misaligned.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install21.jpg

If you end up having your gas-tube in the receiver even slightly crooked, it could cause some ugly things to happen when the bolt slams home, so check it well.

#6. Now that you know all is well, the only thing left is to install the main body of the tube.

Slide the tube over the receiver nut, making sure the body is oriented correctly so that all the screw holes line up correctly. Screw the receiver tube into place, making sure that the 4 short screws go in the lowermost holes, and the 2 longer screws go in the top.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install22.jpg

#7. Reinstall your gas block/tube, check alignment a final time, then re-tighten the GB set screws.

[img width=800 height=600]http://i214.photobucket.com/albums/cc158/jm_cross/FFT_Install23.jpg

#8. Put the upper back on the lower, and give yourself a pat on the back. Your FFT is done! This took me about 1 1/2 hours to do, and that includes the heating time, running around looking for stuff, etc. With tools and everything in place, you can do it in 1 hour flat. How does it look?


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Got my VTAC the other day & been so busy I have not had time to take photo's . It was worth the wait that's for sure . I ordered a full length fail ,so it will not be put together until it arrives.

My hand guard nut is just slightly off from being in alignment for the gas tube with it tight . I will lap some off the back face to get it to tighten with out the use of loc tight as there instructions say.

This is going to be a iron sight rifle only ,so I have to get the rail lined up with the top rail of the upper & of course make sure the gas tube is good to go. I have it mocked up & will take some photo's  to post .

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If the nut is sufficiently difficult to turn, you could always back it off again until the gas tube hole re-aligns. I did NOT turn the handguard nut all the way back against the receiver, there should be a small gap there. Remember that if you're not using the loctite, use a small pin or something to align the handguard nut to receiver (and hold it in place) so things aren't shifting around when you torque the barrel nut.

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You have nice hands, Matt.  <thumbsup>  Not being gay in anyway, but this article wouldn't be nearly as good if you had those great big, skinned up, nasty gorilla hands in all the pics.  <lmao>  Good work, man.

Also, I like that your bottle of Anti-Seize looks well used... 

That says alot about a guy, right there.  <thumbsup> <dontknow> ;D

Good stuff, man, good stuff. 

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If the nut is sufficiently difficult to turn, you could always back it off again until the gas tube hole re-aligns. I did NOT turn the handguard nut all the way back against the receiver, there should be a small gap there. Remember that if you're not using the loctite, use a small pin or something to align the handguard nut to receiver (and hold it in place) so things aren't shifting around when you torque the barrel nut.

Why would you need a gap between the hand guard nut & upper receiver ? If the hand guard nut is tightened up to the & against the upper ,would it not be like a monolithic , one piece upper ? Will it make a diff. ?

I just ordered my upper rail ,so it will be a couple of days before I even get a chance to play with the assem.

I will try to take some photo's in the AM (got to work again tomorrow night )

You will see in the photos , that my hand guard nut is only a hair away from lining up with it snugged against the upper.

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You should go whatever direction makes you feel best about it. I was simply making a recommendation based off of what I feel would be less difficult, I didn't understand that you wanted it to be like a monolithic rail. TBH, the only difference between joined rails and a monolithic rail that I can discern, is that the monolithic rail rests atop the receiver and forearm rails (or extends from the forearm to atop the receiver) and doesn't have any breaks in it. Besides cosmetics, I don't think a small gap would create any problems for you with regard to mounts that bridge the gap,  unless you the tensioning device for the mount were directly over the gap.

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I will have to look when it gets here ,but there may have to be a gap for the proper positioning of the full length rail.

I will also have to look at the instructions more closely when I get a chance. I will have to back that HG nut off almost a full turn . We will see what it looks like both ways when the rail gets here .

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My rail should be here today ,so I can assemble the upper. Look how close the Vtac is to being aliened & up against my upper .

My referance to the monolithic upper was just a comparison on why wouldn't the Vtac work fitted tight against the upper receiver . It should not interfear with the fee float bbl. & the benifit IMO would be a stronger upper assem.. Being the hand guard is just not supported by the upper threads ,but the rail will tell me how it will go together. Or I might have to take a little off of it . <thumbsup>


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I finally got time to see if I could lap the hand guard nut to fit up tight against the upper . It did not take much lapping with 600 grit to get it there . It seemed to only take off surface ridges & the Finnish was not taken off at all . You can see in the following photo's that its a nice fit .


The full length rail has the screw holes slotted for forward & back adj. ,so no need to take any thing off of it .


I use the Brownell's rail alignment tool to make sure it GTG.


I have a used decaping rod from a RCBS rifle die ,I found is almost a perfect fit for the gas tube hole through the upper & hand guard nut  and can use it to check for bbl. nut alignment also



I will post when I get time to assemble the barrel .The only wrench that will fit this bbl. nut is the YHM . I have the combo ,DPMS/AR10,but they don't fit .I remember the problems I had with the Fulton Armory hand guard . It was nice to have a wrench & not have to improvise.


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The tool is great , but it is tight on the DPMS uppers rail. I had to use it backwards of the instructions to put the rail on the Fulton Armory(YHM ) hand guard.

It  fits perfact on the SI Defence upper ,as you can see ,the proper fitment of the tool in the photo.

It is not tightened down yet for proper install of the rail.Photo just for reference.


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The decapping pin did not work as well as I wanted it to . When I tightened up the bbl. nut ,the hand guard nut put some pressure on the rod & I didn't want the HG nut to move at all . The decapping rod is 0.185 in dia. at the shank .

I had another rod that was 0.195 and worked just fine . Every thing is in perfect alignment & I can not budge the HG nut . Will post some photos when I get a chance.

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I got out to the range today to test fire my new 308 build & here are the results ;

Started out with PMag with one round ,all function tests worked except ,bolt hold open (even though it worked in pre test) Tried to set it manually ,but would not hold BCG at all .

Went to Pmag with two rounds in it for function test ,fed both rounds & no bolt hold open last round .

Went to 19 rounds in Pmag , would only fire one round & FTF next round ,used two types of 7.62 & my 172 gr. hand loads ,same results . went to three rounds in mag & worked fine ,four rounds ,fine , five rounds, fine, six rounds ,same problem would only fire first round & FTF next. bolt over on any thing above five rounds with two diff. Pmags .

These mags work flawlessly in my other DPMS build .

Went to CProducts mag,with twenty rounds , functioned as fast as I could pull the trigger, no FTF's, two diff. Cproducts mags. , two diff. 7.62 ammo.

Went to DPMS mags , 19 rounds , fired as fast as I could pull the trigger , no FTF on two diff. mags., two Diff. 7.62 ammo.

Went back to Pmags , same results as above ,no more than five rounds.

The rifle was a blast to shoot ,,a little more recoil then its bigger brother I have, but this rifle with the cheap old turkey scope weighed in at 9.4 # empty & my 20 " is 12.9 # empty.

The bolt stop will get worked on to work ,not a big deal ,but for those who said this 16" bbl with rifle length gas system would not work ,well she just doesn't like Pmags right now .

This was just a function test today ,no targets .

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