Armory Sponsor
Posted: 8/22/2002 7:42:54 PM EDT
| I am trying to zero my new upper using the 50 yard procedure with XM193 ammo. With the rear sight cranked down to 8/3-2 and the front sight screwed all the way up I am hitting 3.5" above POA. Want impact point to be POA. Does anyone know if any supplier makes a higher front post or does anyone have another suggestion? |
|
I just had the same problem. I had a Colt upper receiver with a Bushmaster Barrel. Couldn't zero properly and the front sight was all the way up, almost falling out. Colt upper receivers/carry handles have a different sight height which causes this problem. I sold the Colt upper, bought a Bushmaster upper, swapped the barrel and it sighted in fine. I asked this same question about 3-4 months ago when I had the problem and was kindly advised by other forum members of the difference with the Colt part dimensions and aftermarket part dimensions. Good luck. Hope this helps. |
|
There is no difference between the height of a Colt flat-top receiver and other brand's flattop recievers (except for some older Oly's, or the cast DPMS "Lo-Pro" and "Hi-Rise" uppers). What IS different is that the detachable carry handles and front sight blocks used on Colt M4s are slightly taller than standard (meaning: the standard Colt originally set with the M16 and the first flattops). The taller front sight bases are stamped with an "F", but there aren't any markings on the carry handles. Other manufacturers use Armalite(original)/Colt's original standard for all parts, and are interchangable. -Troy |
|
Presumably when you’re at 8/3-2, your rear sight assembly - the part that moves up and down - is physically very nearly as low as it can go (by probably two or three clicks). If it seems higher than it should be, you can lower it. Basically, the elevation drum is in two pieces, a mostly internal threaded piece that actually moves the assembly, and an external piece with the drum markings. These two pieces are linked by a small hex screw accessed through a hole in the top of the sight assembly. Loosening the screw will allow you to change the relationship between these pieces and actually lower the sight (till it bottoms out) while lining up any markings you want. However, more likely you need a higher front sight. DPMS sells one. See: www.shooterstore.com/acb/showdetl.cfm?&DID=90&Product_ID=11538&CATID=494 And, of course, as you've already recognized, you might just be using the wrong aperature. |
Armory Sponsor