AR-15 Rear Sight Question

G

Gregory Gauvin

New member
I ordered a rear sight assembly from R&R arms (DPMS). The packaging had opened during shipment, and several parts were lost (the small sight springs, ball bearings, a roll pin, aperature...) This was corrected with a phone call to them. Then I was shipped duplicate parts. Today I got off the phone with DPMS, and I believe my problem will be solved when I receive the last part I'm missing - the windage knob retaining pin. Since I have all the parts but the windage knob retaining pin, I decided to go ahead and finish putting my rifle together and just hold the windage knob on with a paper clip until the roll pin arrives.

I'm experiencing a problem or I don't know what I'm doing. The threading on the rear sight base is more or less a fine thread, and the threading in the elevation knob is course. The elevation index knob slides up on the base fine, but the elevation knob won't go on. Do I have mis-matched parts?

Is it possible the sight base is threaded for 1/4 clicks or 1/2 clicks and the elevation knob is threaded for 1 MOA adjustments? Can this be my problem? Did R&R arms send me a messed up rear sight kit or am I doing something wrong here?
 
Sounds like you got it figured out. What was the sight supposed to 1/2 or 1 minute adjustments?? They just need to send the matching part for whichever thread you ordered.
 
Correct...I almost have it figured out.

I need the elevation knob with the correct threading. However, it appears there are only 2 types of sight bases...the "standard" with course threads, and the fine threads. Would that mean the sight base I have with the fine threads is a national match?

They also make replacement elevation knobs for 1/2 MOA adjustments with course threads. The elevation knob I was sent has 25 notches around. So wouldn't that make it 1/2 MOA? And 1 MOA has like 12 notches or something? What determines 1 MOA from 1/2 MOA, the number of clicks on the knob or the threading of the sight base?

Thinking I was sent a NM sight base, how could I determine this? What parts are needed to go from 1/2 MOA windage adjustments to 1/4 MOA? There are 12 click detents on the windage. According to bushmaster, they make a replacement knob that converts 1/2 MOA windage to 1/4, but wouldn't you need 24 or so detents on the sight base for this to work?

How many MOA are the windage markings on a sight base? It takes 8 clicks to move 1 notch on my sight base. If each notch is 4 MOA, then I have 1/2 clicks, but if they are 2 MOA, then I have 1/4 clicks. I ultimately would like to have 1/2 MOA windage and elevation.

So, my confusion remains. If the stand is 1/2 click windage and 1 MOA elevation or 1/2 MOA elevation, what's the point in having 2 types of threading of a sight base when 1/2 MOA elevation can be achieved with the courser thread?
 
If i bought a sight from some company and it came in pieces with parts missing i would be sending it back and either asking for complete sight or my money back...
 
mrnkc,

You are right. This has been frustrating as all heck. Although R&R arms are polite and friendly on the phone, whoever packages the parts are partially if not fully, retarded. I figured out my problem. They sent me mis-matched parts and to make it even worse, I now have to order the correct elevation knob because I waited too long to make a claim because I had been waiting to put the sight together until they had sent me all the missing parts.

To make matters worse, if you go to their website, the parts are not labeled correctly. Their NM AR-15 rear sight assembly and NM elevation knob is marked as providing 1/4 MOA windage and 1/2 MOA elevation. It SHOULD be labeled as 1/4 MOA elevation and 1/2 MOA windage. Their mis labeling had confused me to the point of which I had thought that I had become stupid.
 
nm sights

Most NM sights are 1/2 elevation and 1/2 windage. tyhe finer adjust to 1/4 is usually found on windage only. I have a Rock River and it was 1/2 x1/2 until I changed the windage to 1/4. I think the 1/2 threads are 32 tpi and the 1/4 are64tpi(my memory may be incorrect)
 
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