Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login

Site Notices
Posted: 12/8/2003 8:16:38 PM EDT
Well I ordered a short FF RAS and it's on its way.  I have looked at the instructions for installation shown here: www.knightarmco.com/faq.htm  The pdf file given in the link doesn't have any text and doesn't really go into any detail.  From looking at the instructions though, I think I have a pretty good idea on the basics of what I need to do, but would like some additional insight from anyone who has experience with installing one of these handguards.

I should mention that I am already half the way there.  I have already removed the front sight base and the barrel.  I was a bit anxious about getting the front sight base off, but it actually went fairly smooth.  I kept the gas tube attached to the FSB since the instructions show that they need to be attached when the FSB is reinstalled.  Had one person hold the barrel with the front sight resting on a rubber mallet head and used a 3/8" brass punch to knock the taper pins loose.  Took about 5 good whacks on each pin, but they came out and the ends didn't get mushroomed so I should be able to reuse the pins.  Have read using a steel punch can deform the pins as well as leave pretty good gouges on the FSB, so I am pretty glad I bought the brass punch.

Actually, I was really surprised this step of the process went as easy as it did, have read multiple horror stories on this site on getting those pins to move.  This was a Colt barrel though, so maybe that did help some, have heard that on Bushmaster barrels the pins can be much more difficult to remove.  

One thing I did notice is that the brass punch left some brass marks on the FSB and they have been somewhat difficult to remove, even with Barnes CR-10 copper cleaner.  I think it would have been a good idea to have put a decent coat of CLP on the FSB beforehand so that any brass marks left on the FSB would have a layer of CLP underneath them to ease removal.

Once the pins were out, I had to tap on the FSB with a rubber mallet to initially free it from the barrel since it was press fitted on fairly decently.  Then I just removed the barrel nut and the barrel and now I am currently waiting for the handguard to show up so I can install it.

So not that I am ready to install the new barrel nut, is there anything I should be aware of?  Hopefully, the barrel nut will index well so I don't have to really torque it.  I have an upper receiver vice block and improved barrel wrench on the way from Bushmaster.  I also went ahead and forked over the cash for the moly-slide paste for the barrel threads, didn't cost that much and figure I may want to remove all this stuff down the road, which the paste should make easier to do.  I am currently not planning on using a torque wrench, but I can get one from a friend if necessary.  I figure I will just hand tighten the barrel nut and then use the wrench to index the nut to the next gas tube hole.  Have read about installing the carrier and using a spare gas tube to help index the barrel nut.

Question 1:  If indexing the nut does prove difficult and I have to really crank on it, is it ok to go over 80 ft-lb spec?  I don't think I want to be down in the 30 ft-lb range since the use of a forward grip will add some torque to the handguards, and I have read that the handguard ring is tightened in the reverse direction to the barrel nut and may cause it to come loose.

Once the barrel nut is on and indexed, next comes installing the index pins, handguard, and handguard ring.

Question 2:  Does the FSB/gas tube combo need to be installed before the handguard ring is tightened down?  If so, is it just to make sure that the barrel nut does not come out of alignment with the gas tube hole in the receiver?

I have read that getting the top rail of the handguard perfectly inline with the upper receiver rail can be tricky.  I was thinking of attaching my removable carry handle or ARMS #35QD mount to the both the receiver and handguard to keep them in line as I tighten down the handguard ring.  Hopefully there will be enough clearance for the strap wrench to fit between, I guess I will see when I get the parts.

Question 3:  If there is not enough clearance, are there any other tips anyone could provide to get the handguard and receiver perfectly aligned?

Question 4:  Should I use the moly paste on the handguard threads?  Any downsides to doing this?

At this point, the only thing left is to reinstall the taper pins.

Question 5:  Is there any pitfalls I need to be aware of in getting the FSB back on and the pins back in?  Before I removed the pins, I noticed that they stuck out about the same amount on each side, so I figure I will just pound on them until they are in that configuration.

Well that is about it, if anyone is still reading this long-winded post, I would really appreciate any guidance one could offer.  Thanks.
Link Posted: 12/11/2003 8:58:09 PM EDT
Just a bump to see if anyone bites.
Link Posted: 12/12/2003 6:29:01 AM EDT
[Last Edit: 12/12/2003 6:36:49 AM EDT by IPSC_GUY]
Well If you have the front sight base off you are MUCH more than half way. That is the biggest pain you are going to encounter. Installing the knights FFRAS is very simple. To answer a couple of question.

Find a torque wrench if you can but if you can't and you can questimate your pressure, you should be fine. When you go to tightening the new barrel nut tighten and loosen it three times to help spread and set the threads. After that do your final tighten and alignment. The moly lube will help a great deal. I have heard that bushmaster simply uses 30 weight motor oil. As for indexing this may take some time. It goes like this, tighten put the two small aligning pins in the barrel nut put the RAS on, tighten the ras locking ring by hand and eyeball it to see if the top rail lines up with the rail in the flat top. At this time you can slide your FSB with the gas tube in it back on the check to see if it goes through the holes and into the upper fust to make sure. When it does (and it should) get a small strap wrench and snug down the ras locking ring, reinstal your FSB and you are done. The Knights FFRAS is by far the best design of all the float tubes out there. Too Bad they are so expensive. If ya run in to trouble don't hesitate to IM or email for help.

IPSC_GUY sends
Link Posted: 12/12/2003 5:56:29 PM EDT
The only point I'll add is that the pickier you are about getting your barrel nut indexed perfectly the better your rails will line up.  After I installed mine the rails were in perfect alignment.
Link Posted: 12/12/2003 9:22:22 PM EDT
[Last Edit: 12/12/2003 9:33:19 PM EDT by jason_h]
I just got the rail in yesterday and notice from dry fitting it that alignment is much more dependent on getting the barrel nut indexed correctly.  Also noticed that you can't get the handguard to engage the aligning pins until the handguard ring has been screwed on most of the way.  As a result, I figure this will take some time removing and reattaching the handguard until everything is perfect.  Also realize now that needing to index the nut for the gas tube hole is irrelevant, since if the gas tube hole isn't lined up then the upper rail won't be lined up with the receiver rail.

Also noticed that the idea of using the carry handle to adjust/check alignment won't work since it contacts the handguard ring.  However, the ARMS #35QD base works perfectly for this and even leaves enough room to get a strap wrench around the handguard ring while it is attached to the upper.

Will definitely use moly grease on both the receiver threads and the handguard threads since it looks like this would make it much easier to get proper torque on things.  Unfortunately the tools I need haven't shown up yet so I got to wait until next week before I can get the handguard attached properly.

One other question, what if you over indexed the barrel nut slightly, installed the pins and hanguard, and then when applying the torque necessary to snug down the handguard ring, you applied enough to rotate the whole handguard/barrel nut assembly back the other way until it came into alignment with the receiver.  The only bad thing I can think of happening by doing this is that you may have to over torque the handguard ring to move the barrel nut, and moving the barrel nut back the other way may cause it to further loosen up down the road.  On second thought, maybe I will just stick to the trial and error process, making sure that there is moly paste on the interface b/w the handguard ring and barrel nut to reduce the chance of loosening the nut.

Well, thanks for the replies, they have been very helpful and I will have to update when I get everything done.

Edited to add that I notice last night that all taper pins are not created equal.  To get both pins to enter into the front sight base and/or barrel to the same degree, it was necessary to have the right pin in the right hole.  If I switched the pins around, then one would stick out further than the other when just pushing them in by hand.  Maybe it was just a fluke, but it makes me wonder if at the factory they have different size taper pins so that if one hole is drilled a little larger than the other, they can still pound both pins in to the same depth.
Link Posted: 12/17/2003 8:52:45 PM EDT
[Last Edit: 12/17/2003 8:55:05 PM EDT by jason_h]
Well not that anyone cares, but I thought I would add a final update to my installation of my KAC FF RAS.  Got the tools in yesterday, including a heavy duty barrel wrench from Bushmaster, talk about a chunk of steel, got to lift weights just to use the thing.  Anyway, got the handguard on without too much trouble.

Ended up following the TM and torqueing the nut three times.  Found out that each time I torqued the nut to roughly 30 ft-lbs, the nut went on a little further.  Unfortuanately, by the third time, I was just barely pushing 30 ft-lbs of torque to get the nut indexed correctly.  Not sure if it will loosen up on me in the future, guess I will just have to see.  There was no way the nut was going to go to the next gas tube hole without destroying the threads on the upper receiver.  In the future I might just torque the nut the number of times needed to get up into the 50-80 ft-lb range.

Used the trial and error method (discussed above) of getting the handguard properly aligned with the upper receiver rail.  By sighting along the top of both rails, it was pretty easy to tell if the rails were in alignment.  

Once things looked good, and the handguard ring was hand tight, to keep the upper receiver and handguard rails aligned, I attached one side of my arms #35qd base to the upper and the other side to the handguard rail without the throw lever on the hanguard side being tightened down so the handguard could slide fore and aft in the mount.  This left enough of a gap between the mount and handguard ring to fit a strap wrench around the ring.  At this point the idea was to torque the ring to the point that the rubber strap would slip.  Well I ended up torqueing the ring to the point that the rubber strap broke, guess I will need to make a trip to Sears.  Anyway, I figure I applied somewhere around 40 ft-lbs of torque to the ring so hopefully it won't be going anywhere.  

Did lube the handguard threads with CLP beforehand to ease installation.  Not sure if this was a good idea or not but the impression I got from other people who have installed one of these handguards is that it is a good idea to get the ring fairly tight to reduce flex in the handguard. I figured the CLP would help in this regard.  Guess I will just have to see if it stays tight or not, only time will tell.

Then just installed the front sight, re-tapped the taper pins, and presto, I was done.  Overall, the process was pretty easy thing to do and I probably way over-obsessed about it as evidenced by the length of posts in this thread.
Link Posted: 12/18/2003 5:16:46 AM EDT
Sorry I missed your thread earlier but glad to see it worked out.  As you see, the biggest trick with mounting any barrel is the front sight removal and then the barrel nut.  It is funny how adding and removing the barrel nut 3, 4, 5, 6 times can get you that extra little bit to alighn the gas hole to where you need it.

Now you need to spend a fortune to load the rails...
Link Posted: 12/18/2003 9:38:06 PM EDT
Originally Posted By jason_h:
Well not that anyone cares,.....
View Quote

I do. I have been following this thread, as I am considering the same installation. I have gained a ton of knowledge by reading posts like yours and finding out what works and what doesn't.

Thanks for sharing with us.
Link Posted: 12/20/2003 12:11:24 AM EDT
Thanks for the replies guys, nice to know I wasn't talking to myself, heh.  If you have any questions Mick let me know.

Just a few final things I learned, if one uses moly paste, use it [b]sparingly[/b].  That stuff is like ink, a little bit goes a long way and is a pain to clean up.  Also, 30 ft-lbs is a pretty decent amount of torque and is probably sufficient to keep the nut in place.  The reason I say this, is that on closer inspection, I noticed my handguard rail is ever so slightly canted to one side.  Not enough to make any difference, and I don't think I could get it closer if I tried.  Anyway, it was canted slightly in the opposite direction I was tightening down the handguard ring.  Now I applied a pretty decent amount of torque to the ring (enough to break the strap wrench although on second although probably not anywhere near to 40 ft-lbs I estimated above), more than I could ever apply by hand, and it didn't budge the barrel nut.  If it had, the rail would have rotated and stop when it contacted the other side of the ARMS mount, causing the rail, if anything, to be canted to the other side.  The reason 30 ft-lbs seemed like such a small amount of torque to me was probably due to the size of the barrel wrench I was using, the wonders of moment arms an all that, and also like I said above, that thing is hell-for-stout.
Link Posted: 12/21/2003 10:52:54 AM EDT
[Last Edit: 12/22/2003 2:17:45 AM EDT by G3k]
Hwy guys, I was wondering how tight you ended up getting the nut that secures the handguard.Were there any threads at all visable?
I installed a MRE ras unit two night ago and could only get it down to about a thread and a half visable ,is it supposed to be all the way against the handguard? How much flex do you guys get with you Free float tubes, mine can move  1/8 or so with pressure on the forend in front.I just want to see if it's normal or if that nut is still to loose (like me [:D])
Link Posted: 12/21/2003 3:24:43 PM EDT
Some may not agree, but I have always used med. strength loc-tite on the threads, then just tighten it up hand tight, then to the next alignment hole.  I have never had a problem, you won't stretch threads, and it will never come off without tools.  Let it set before installing float tube, and then do the same thing.  Unless you are going to be removing the assy. all the time, why would you use oil/grease on something you want to stay on?
Link Posted: 12/25/2003 6:39:30 PM EDT
G3k, I have about a thread to a thread and a half still showing on mine.  There is a little flex noted when I pinch the barrel and hanguard together.  The consensus according to this thread [url]http://www.ar15.com/forums/topic.html?b=3&f=12&t=174745[/url] is that it is the barrel flexing, not the handguard.  I guess you could put the upper in your receiver vice block and see where the flex is really coming from.

I just took my rifle out a few days ago for the first time since installing the handguard and put 180 rnds through it.  Nothing loosened up and everything is still where is was when I started.  

I was a little skeptical about the need for a front vertical grip, but after putting my rifle through its paces with it on and off, it definitely is a worthy addition to one's rifle, especially if you are wearing gloves.
Link Posted: 12/25/2003 11:02:43 PM EDT
Thanks for the info, that thread and yours being the same makes me feel better!
Have a Happy New Year [:D]
Top Top