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Posted: 11/2/2005 8:44:38 PM EDT
| this regards the f.s.b. that brownells sells(Y.H.M. & DPMS) without holes. is there a special drill to use? or do you just use a series of drills. I will not use set screws so dont even go there. Please describe the procedure. I have a sight allignment tool from Armalite that I intend to use. The barrel is a colt sporter target without bayonet lug and it is going to get one. Thanks Guys. |
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You will need a stout drill press or a mill. You will also need some type of fixture to securely hold the FSB and the barrel in perfect alignment with the indexing pin (in the barrel extension) while you drill and ream the FSB and barrel as a unit. Not sure of the drill bit size, but the proper taper reamer is a 2-0 taper reamer. Doable, but not your average DIY project. Good luck. |
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BTW - just so you'll know. Set screw gas blocks work fine. Been using them for several years and never had a problem of any kind. Just tighten them like you would the lug bolts on an automotive wheel - ie don't tighten one up all the way then the next - tighten each one little by little. And they are sure easier to remove! I like the YHM double pic rail gas block with a folding pic mount front sight base. You might try one - they are inexpensive and I've never had any kind of gas leak. Also some really high dollar AR's use set screw gas blocks. |
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I've tapped the hole under the sling swivel attachment and installed a set screw. Go out to the range, and sight in, tightening the screw when your front sight is centered. Then drill and pin without removing it from the upper. The sight alignment tools are kind of like a bore-sighter, they'll get you on paper but they're not meant to give you an exact zero. ETA: If there's already a pinned on sight in place, it's going to be trickier because they're no set spec for the distance between/placement of the pins. |
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I own a sight allignment tool because the set screws in the fsb on my dpms DCM upper fell out and my sight shifted. So in a panic I went to armalite and bought the allignment tool . I had to do this on my tailgate in the parkinglot at camp perry I have never seen a taper pin fall out. I have a freestanding drill press with a cross slide vice mounted to it. What I intend to do is mount the barrel to an A2 upper then install the FSB. Next I would set the sight allignment tool and clamp it to the barrel using grip clamps this should hold the FSB where I need it. If I set the fsb in a block like the one adco sells and clamp it into my cross slide vice then secure the barrel to the table and vice I should have a fairly sturdy setup . I have all of that figured out. my question is. do I drill the diamiter of the small hole on my old FSB straight through then switch to a hi speed tapered reamer to get the taper I desire? Does anyone have any additonal suggestions? ( other than send it out and have it done ) I am adiment about doing everything that i possibly can myself. My wife calls it Stubbron Krout Syndrome. |
I've never done taper pins, the sights I have drilled and pinned came from ArmaLite and had 1/8" dowel pins, I just put a 1/8" bit in the chuck and drilled them and drove the pins in. Once I had the sight aligned and tightened the set screw down, I didn't need any additional clamping or alignment, the set screw held it in place quite well. I just used a standard drill press vise. |
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