Token Posted October 11, 2015 Report Share Posted October 11, 2015 I made a order to Brownell's recently and among other things, I got a DPMS carbine quadrail handguard [$40!! Still available too!] and a 936 micro gas block [$20!!]. I'll be scoping my rifle, and I want to replace the simple tubular handguard on my Gen1 AP4 rifle and dispense with the A4 front sight/gas block. However I am somewhat at a loss at how to begin. I assume I can remove the A4 sight/gas block simply by removing the pins...any tricks or issues to be aware of here? Does it matter which way I drive the pins out?Will the handguard simply unscrew after I take the sight off? The quadrail piece includes a barrel nut and lock ring, so I'm hoping I don't need any other parts. Your guidance would be most appreciated.... Quote Link to comment Share on other sites More sharing options...
Robocop1051 Posted October 12, 2015 Report Share Posted October 12, 2015 (edited) Tools you will need: a hammer, a punch pin set, a front sight removal block, an AR15 armorers wrench, a large table vice, and some kind of vice block. 1. Pull back on the delta ring, and separate the handguard. Remove both halves.2. The front sight is held in place with "taper pins". As the name implies, the pins are fatter on one side vs the other. They must drive out from the left to the right side. The block will make this effortless and take all the guess work out.3. To reuse your gas tube you'll need to drive out the roll pin. There's no special hint I can give you to pull the tube out. If it's stuck, keep pulling. Some solvent/lube (breakfree) couldn't hurt.4. Clamp the upper into the vice block of your choice. Use the armorers wrench to remove the Delta ring assembly and barrel nut. You may have to remove the muzzle device at this point, to remove/replace the gas block and delta ring. 5. Install your new parts per their instructions. Edited October 12, 2015 by Robocop1051 Quote Link to comment Share on other sites More sharing options...
Token Posted October 12, 2015 Author Report Share Posted October 12, 2015 Okay...the DPMS Gen 1 LR-308 AP4 I have doesn't have a delta ring...it has a solid floating tubular handguard, like this one. I'm afraid it is just not obvious to me how that handguard is supposed to come off. Youtube has lots of videos on how to remove the regular 2-piece delta ring units, but it seems nobody wants to remove a floating handguard from this particular rifle. I am particularly concerned that there might be some hidden set screws or other locking devices that I will be working against and potentially causing damage by using ignorant force because everything seems 'stuck'. Since there is no milspec standard for the construction and assembly of these rifles I am not inclined to trust the Youtube videos where people are working on AR15s that do have such standards.Robocop -- I appreciate your advice but I think my problem needs a sharper focus on the specific situation. Quote Link to comment Share on other sites More sharing options...
blue109 Posted October 12, 2015 Report Share Posted October 12, 2015 (edited) Hey token...no set screws, but DPMS locktights those bad boys on. You should be able to see a small seam on the receiver side of the tube, probably an inch or two away from the end. The long piece is the threaded freefloat tube and the short piece is the actual barrel nut. You just need to unscrew the tube from the barrel nut which will give you access to it. The holes arranged around the barrel nut are for the gas tube at the top, and the studs on the armorers to remove it from the upper. Usual practice is to heat the tube at that area to loosen the lock tight and then use a quality strap wrench to break it loose. Or the short version...they glue that Damn thing on, so get a bigger hammer and get busy. Obviously the front sight needs to be removed first. Those taper pins can be unreasonable, so if they aren't coming out...hit them harder. Edited October 12, 2015 by blue109 Quote Link to comment Share on other sites More sharing options...
EasyEJL Posted October 12, 2015 Report Share Posted October 12, 2015 Just because it was mentioned here, i'll threadjack for a sec. How do you put one of those FSBs back onto another barrel? I got a 308 carbine barrel i'll be taking one off of, and sometime later buying a 5.56 20" barrel and need to put the FSB on to save the money of buying one already set up if possible Quote Link to comment Share on other sites More sharing options...
blue109 Posted October 12, 2015 Report Share Posted October 12, 2015 Problem is that barrel was drilled for that fsb and those taper pins. Likelihood of it lining back up on a different barrel is slim. If you are dead set on reusing a fsb on a new barrel, you usually have to have it drilled. Aftermarket barrels usually won't even have the taper holes drilled unless they are "take off" barrels someone is clearing out. The expense of sending them off usually negates any money saved on reusing the FSB. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted October 12, 2015 Report Share Posted October 12, 2015 STD A2 Sight type gas block has Tapered pins & are removed with pin punch from left to right , the larger end of the Pin is on the Ejector port side , reverse order to install. Blue109 , stated correctly , its a crap shoot if they do line up , close won't work . There is a special tapered reamer or Drill bit just to make the Holes for the Pins . Buy a Barrel with an A2 sight fitted , as said , all done . Quote Link to comment Share on other sites More sharing options...
Token Posted October 12, 2015 Author Report Share Posted October 12, 2015 Gentlemen -- Thanks for your advice:Robocop -- It looks like I have to order a few more things from Brownell's...in particular a barrel nut wrench for the DPMS LR-308. I just hope it gets here faster than my last order...Blue109 -- That's the info I was looking for. Good to know about the Loctite.Survivalshop -- thanks for confirming how the pins work. I won't be reusing myfront sight....my LR-308 will be scoped and set up with removable BUIS. That's one of the reasons I want to mount the quadrail in the first place... Quote Link to comment Share on other sites More sharing options...
washguy Posted October 13, 2015 Report Share Posted October 13, 2015 Hey token...no set screws, but DPMS locktights those bad boys on. You should be able to see a small seam on the receiver side of the tube, probably an inch or two away from the end. The long piece is the threaded freefloat tube and the short piece is the actual barrel nut. You just need to unscrew the tube from the barrel nut which will give you access to it. The holes arranged around the barrel nut are for the gas tube at the top, and the studs on the armorers to remove it from the upper. Usual practice is to heat the tube at that area to loosen the lock tight and then use a quality strap wrench to break it loose. Or the short version...they glue that Damn thing on, so get a bigger hammer and get busy. Obviously the front sight needs to be removed first. Those taper pins can be unreasonable, so if they aren't coming out...hit them harder. EXACTLY ! Wash Quote Link to comment Share on other sites More sharing options...
392heminut Posted October 13, 2015 Report Share Posted October 13, 2015 Obviously the front sight needs to be removed first. Those taper pins can be unreasonable, so if they aren't coming out...hit them harder. I think someone once said on the board here to "Beat them like they owe you money!" Quote Link to comment Share on other sites More sharing options...
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