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Posted: 7/4/2004 9:28:23 PM EDT
| What does it entail to install a DD forearm...Just removing the front sight..I do not have a muzzle device..so everything should slip off after the sight comes off right? |
ARs are easy to work on, but not THAT easy  You have to punch out the tapered pins of the FSB, no need to punch out the gas tube since it can just slide off the barrel while still attached to the FSB. Next, remove the barrel nut. You'll need an upper receiver vice block, a vice, an amorer's wrench, hammer, drift punches and a torque wrench. |
Here's a small number of FSBs I've successfully removed with out damage to the barrel, the FSB or to a Dremel cutting wheel (never need one). I've removed and installed a few more than that. The keys are: 1. Hitting the SMALL END of the pins first. 2. Make your first hit a good one - I use a slightly oversized pin punch and a small sledge, with the FSB/barrel supported with 1" X 3/4" X 6" strips of oak. One or two good, hard wacks with the sledge gets the pins moving. It may suprise some people how hard I hit the pins the first time, but the pins take it very well and show little to no effect from the hit. If you pansy around and mushroom the end of the pins, then you are in for a long day.  3. Finish the pins with the correct sized pin punch and a regular hammer. I don't normally soak the FSB in Kroil or penetrating oil unless the pins take the first couple of wacks and don't budge, but that is never a bad thing to do up front. Less than a 10min job!  The barrel nut is also pretty easy with the proper tools.    I always use the bottom wrench for final tightening, I occasionally use the top wrench for hand tightening. As you can see, my DPMS multi-tool shows a "little use". Set up the receiver assembly in a vise with a vise block. I've found that barrel nut tools like the DPMS multi-tool work better that the two or three pin tools in taking off barrel nuts. The two/three pin tools don't have enough surface contact to allow taking off a stubborn barrel nut without smearing the barrel nut teeth right off the nut. The DPMS multi-tool has about 3/4 contact with the barrel nut teeth and usually can "get-R-done" without damaging the barrel nut. The only frustrating part is holding the tool on the nut with the delta assembly trying to push it off while your are holding it on with one hand and trying to hit the other end with a hammer to break the nut loose. When tightening a barrel nut, there is a recommended torque that the TM says you should torque the barrel nut to. about 50% of the time, this torque leaves you with misalignment in the gas tube port of the receiver and a tooth/hole in the barrel nut. This leaves you with two options. 1. Loosen the barrel nut to get alignment. NEVER a good idea. 2. Tighten more to get proper alignment. This is why is is always a good idea to use some type of lubricant on the receiver/barrel nut threads. You have a 50/50 chance of having to exceed that torque to get proper gas tube alignment and dry threads don't take torque that well, they tend to hold more and get damaged, especially with aluminum threads vs. steel threads - which set of threads will win  .Total time to install a DD forend - about an hour, give or take a few minutes. Total cost of tools - around $25 for a multi-tool and around $40 for a good vise block. If this is a one time event for you, it may be more cost effective to send it to a reputable place like ADCO, but if you are an AR addict (like me) and see multiple builds down the road, it may be wise to buy the tools. My tools have payed for themselves many times over now.
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Bushmaster? RRAs are a piece of cake to take off and on. Bushmasters, I gladly pay Schuster to mill out the pins. |
| Yep, I'd say you do. Difficulties in removing them are the norm. It's not for lack of trying and equipment either. While I only have one hammer and an inadequate work bench, a friend that has all the tools in all sizes pounded on it for 30 minutes (this time a Colt barrel), eventually we gave up. |
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h8mtv, This is the one I use. Just have to be very aware of twisting A3/A4 receivers if you plan on using excessive force to tighten or loosen a barrel nut. I haven't had that problem yet, but if I keep fooling around, I'm sure I'll run into a real stubborn barrel nut one of these days. Duffy, I've done a few Colt barrels FSBs also. No problems there, either. Like I said, that first hit is the key, IMO. An unsuspecting barrel owner watching me remove the taper pins would probably crap their pants when they saw how hard I hit the pins with the first couple of hits. But it works, so go figure. 
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I've done work for others and h8mtv has seen my handy work up close, but the deal fell through because of an error in judgement on my part on one of the parts (preban vs. postban on a "muzzle brake" - sorry about that, Sean, but all is better now). I would do any FSBs (for the price of shipping to and from) for anyone who was willing to pay the shipping. I wouldn't expect anyone to trust a total stranger, but I'll throw the offer out there, especially for anyone close. I don't have the problems that some people have and I absolutely HATE to see perfectly good parts Dremeled off. That is by far my largest pet peeve when it comes to AR builds/maintenance.
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| Duffy, how about the rear pin by the bayonet lug that wouldn't come off of the barrel- Like it was welded on. I cut through the right and left side of that rear "ring", so the whole FSB was gone and the only thing left was the lower half ( imagine "U" shape) of the rear hole, the part with the bayonet lug on it. Had to hit the bayonet lug 3 times with a hammer before that piece of metal and the pin dropped off the barrel. If you still have that piece left over in your drawer, take a picture and post it! |
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