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Posted: 1/12/2009 7:40:51 AM EDT
I had to sight my DPMS DCM upper in almost all the way to the right on my rear sight, leaving only a few clicks remaining for windage. Is it possible to move the frint sight block to the right a little bit (or the barrel)? I cant belive they would send a DCM out like this. 
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Yes anything is possible but this is the wrong solution. Your issue is with the way the barrel was put on to start with. Your barrel needs to be redone by someone that knows what they are doing and that alone will reduce your rear windage to normal limits.
Easy fix. Please leave the front sight base alone. |
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The front sight uses four set screws instead of the two driven through taper pins.
These set screws are used to index the FSB from side to side to zero out the rig with the rear sight set dead center, Hence loosen one side while tightening the other side will readjust the FSB for the needed FSB Zero. As for DPMS setting.adjusting the FSB on a CMP rifle/upper, why would they bother? Until they knew the excate match ammo that is going to be shot through the rig, a Bore sighted FSB could still be 4 MOA off, and would still need to be adjusted by the end user when it's all said and done. Instead, they do not final set the FSB, and leave it up to the end uses to both adjust the FSB,and lock the set screws down with Loctite when it's all said and done. 
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DPMS builds the upper without the FSB installed on the upper, and is pretty good about getting the barrel port TDC when they install the barrels (tighten the barrel nuts).
The FSB is installed closed to center top, with a quick check to the gas tube to make sure it's close, but that is it. When you zero out the FSB with live fire, you need to check the gas key alignment as well. Again, this is a CMP rig that the shooter will fine sight tune with the give match ammo he/she will be shooting, and the rifle does not come sight ready/zeroed to go. Furthermore, you will be playing with the rear/front sights up/down combo's until you get perfect 200 yard zero combo, then start marking for a repeat zeros for 200/300/600 on the elevation dial, and the windage dial for a return point as well. If all of this is beyond you, find a CMP HP shooter to help you set up the rig, or get DPMS on the phone to help walk you through the set up/sight tuning. |
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If the FSB is D&T #8-36, it doesn't take much to make a 25 MOA adjustment. Do it by bore sighting, leave elevation alone for now. Take the upper off and secure it to a bench, looking through the bore at a vertical target like a fencepost 25 yards or so away.
Set the rear sight to zero and then carefully adjust the front sight to zero the fence post in the sight picture. You will be on. The FSB has a larger hole than the port so alignement isn't all that critical but if the FSB LOOKS off, then you should look at remounting the barrel. Make sure to index the FSB to center the port. Moly grease on the threads and nut. Hold the receiver with barrel blocks, then adjust the barrel to get windage on with boresight before clamping the barrel in blocks. With both receiver and barrel clamped, the nut can be torqued without twisting the alignment. |
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