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Posted: 5/29/2005 5:11:34 AM EDT
[#1]
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Posted: 6/6/2005 11:10:50 AM EDT
[#2]
Ok then, where would one obtain a true A4 rear sight assembly for a stripped carry handle? I was unaware of the difference when I assembled mine with the standard A2 PK. As you can imagine, it's kind of wacked out right now.
And yes, the damn ball detents eject with extreme force. I lost all three that came with the kit and had to order extras from Brownells. Matt |
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Posted: 6/6/2005 3:36:26 PM EDT
[#3]
The carry handle sight parts are available from Bushmaster, but aren't listed in their catalog or website.
Most parts are the same as the standard A2 sight parts. The only different ones are in red: From Bushmaster Tech Support:
ETA: The elevation spring and retaining pin may be the same as the standard A2, but I include them as being different, as the sight base is shorter and the sping may also be shorter, but I don't know for sure. |
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Posted: 6/9/2005 1:51:28 PM EDT
[#4]
Mongo:
I have a DPMS rear sight with what looks like an A2 elevation thread coupled with an A4 elevation index:  I assume this means my elevation adjustments will not be correct until I replace the index ? Once done, I will be able to zero out to 800M, correct ? w00t  .Is the above corrrect ? |
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Posted: 6/9/2005 2:29:33 PM EDT
[#5]
IMO, you have two options in this case. Either change your index to an 8/3 index and go with the 8/3 sight base, since the 8/3 sight base fits in that particular sight. Or you can go with the 6/3 sight base and your present 6/3 index. Either will require some sight disassembly - just swapping to a 8/3 index would be the cheapest and easiest. |
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Posted: 6/9/2005 4:58:03 PM EDT
[#6]
Thanks Mongo. As the sight is on a 20" barrelled rifle, I've ordered a replacement 8/3 index. After reading your comments about the ball detents shooting across the room, I also ordered a spare one of those
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Posted: 6/21/2005 4:22:34 AM EDT
[#7]
Is there any difference in the windage screws? The RRA catalog shows a "NM" windage screw and a regular windage screw. I'm unsure if the "NM" windage screw applies to regular A2 sights or the A4 carry handle sights.
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Posted: 6/21/2005 5:28:15 AM EDT
[#8]
I don't know. I'll have to check when I get home. I'm thinking there might be, though.
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Posted: 6/23/2005 3:21:27 AM EDT
[#9]
Mongo
I placed an order from Bushmaster for the A4 index wheels and they charged me the A2 index wheel prices: 9349066 A2 Elevation Index , $6.95 9349067 A2 Elevation Knob, $5.95 9349066-1 A4 Elevation Index , $4.95 9349067-1 A4 Elevation Knob, $4.95 I'm trying to square this away with Bushmaster right now, but they overcharged my credit card by $3.00 already, shipped it 2 days after I placed the order when they told me it shipped the day after, and due to this delay I won't get it until next Monday (I placed the order on Monday). At least if they sent me the right A4 parts I can play around with it in the meantime. If not, that's more time wasted because someone thought they were smarter and neglected to ship the "-1" parts thinking it was a mistake. 
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Posted: 6/23/2005 4:37:11 AM EDT
[#10]
Damn. I ordered two complete A4 sight assemblies for some stripped forgings I had, plus the mounting hardware and got everything I ordered in short order with no billing issues. I still haven't assembled one of the carry handles yet. |
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Posted: 6/23/2005 5:09:29 AM EDT
[#11]
I called and it looks like the person that entered the order left out the "-1" part #s.
They're going to ship out a replacement order along with a return packet for the incorrect parts. Sounds like good service so far! I'm just curious, how much did the stripped forgings cost? Is it worth while to build one up or buy a pre-assembled DCH? |
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Posted: 6/23/2005 5:14:40 AM EDT
[#12]
I got them off of e-turd (ebay) for about $20. I bought them just to see if I could build a quality carry handle for cheaper than just buying a complete one. Well, with the Bushmaster pricing, I saved very little, but I learned a whole lot about the carry handles, so overall, I'm happy with what I did. |
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Posted: 6/28/2005 1:35:19 PM EDT
[#13]
Update:
It appears the Tapco Rear Sight bases have a different thread pitch from the A2 and NM/A4 sight bases. The Tapco bases have a tighter thread pitch (more threads) and thus the A4 carry handle elevation wheel will not fit. The index, however, still works. With the carry handle index, and Tapco sight base, there are 6 clicks between the "3" and the "4". However, if you're using the A2 index (which I have because Bushmaster accidentally sent the wrong ones) there are 2 clicks between the "3" and the "4" on the same sight base. The thread pitch is all wrong, so the distance between the #s on the index is meaningless. |
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Posted: 6/28/2005 2:04:20 PM EDT
[#14]
I believe that's the same as my BM handle.
That doesn't sound right, but I doubt an A2 index on a real A4 handle would work out right either. I'd have to get the rifles out to be sure, but IIRC the A2 sights progress with N clicks to go from N to N+1. 2 clicks from 200m IBZ to 3, 3 clicks from 3 to 4, 4 clicks from 4 to 5, etc. The handle is "half clicks" so 2x the A2 number between. 4 clicks from IBZ to 3, 6 clicks from 3 to 4, 8 clicks from 4 to 5, etc. |
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Posted: 6/28/2005 7:08:31 PM EDT
[#15]
After doing some research, I may have found out that there are 1/2MOA and 1/4MOA national match sight bases. I may have to order one to refine my lesson.
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Posted: 6/29/2005 6:19:59 AM EDT
[#16]
Damn... this is getting very confusing!
I'm using the A4 CH index on my sight base and there are 6 clicks between the 3 and 4. IIRC, the A2 index on a A2 sight base will have 2 clicks between 3 and 4 on the same sight base. If I used the a2 index on my sight base, there'd be 2 clicks as well. However, the thread pitch is the big thing here as that controls how much elevation you actually adjust. I cannot use the A4 wheel (with the threads) but it was only $5 and I'm not going to confuse Bushmaster by asking for a refund, or should I? Anyhow, if you look at the A2 wheel there's like 3 threads. The A4 wheel has about 5 threads. The wheel for my Tapco base has at least 6-7 threads in the wheel. Now i'm really confused, what's the proper IBZ technique with my setup? What type of sight base do I have? 1/4 MOA? I'm currently bottoming out the wheel 4 clicks below the 3 and hoping the IBZ works. |
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Posted: 6/29/2005 7:26:47 AM EDT
[#17]
The number of clicks per revolution would be determined by the number of detent holes on the bottom of the wheel. I haven't compared my A4 to my A2, but I assume that's the same. How much elevation change you get per click would depend on the thread pitch, but also on the sight radius. The index markings would depend on the thread pitch, sight radius, and also the ammo being used.
I assume the A2 index is calibrated for M855 out of a 20". Since the DCH pre-dates both the M4 and the M16A4 it's anybody's guess as to what ammo and barrel combination Colt matched that one to. If I remember correctly, the IBZ page at MD-AR15.com says the extra bit of MOA per click from the shorter carbine sight radius offsets the greater drop from the shorter barrel so that zero works for both lengths of barrel, and M855 and M193 are close enough to the same trajectory for a battlesight zero. Beyond 300m it's probably all acedemic anyway since most people are a poor judge of distance. Bottomed out 4 clicks below the 3 and zeroed at 50yds would be the proper IBZ for an A4 carry handle. Since you say your thread pitch is different than an A4, I would say the 3/4/5/6 marks won't be right on your handle. You'll probably have to go more clicks to get to each distance. You'd have to experiment at actual distances to figure out how many and make your own marks, in which case it might be just as good to start with the NM index. Maybe by some sheer stroke of luck the Tapco threads would work out so that the 3/4/5/6 marks are 300/400/500/600yards (the A4 is in meters). IMHO it's not worth the trouble. Just leave it bottomed out and accept that the dial-a-distance is going to be wrong beyond 300m or so. |
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Posted: 6/29/2005 10:04:09 AM EDT
[#18]
Thanks Mike, I can't find any local ranges that go farther than 100 yd anyhow. But I wanted to get rid of that funky NM index for something that looked half-way authentic.
BTW It turns out it IS getting complicated trying to return something to BM. They're confusing my order with someone else's and I wouldn't be surprised if they sent the UPS return tag to someone else by accident. Did I accidentally order from Model1Sales instead? 
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Posted: 7/3/2005 1:57:16 PM EDT
[#19]
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Posted: 7/5/2005 9:30:33 AM EDT
[#20]
Good pics of the wheels. The top-view pics especially show how the distances are spaced out.
But isn't the A2 a 1 MOA click? |
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Posted: 7/5/2005 10:31:21 AM EDT
[#21]
Wooo good question. I'm not sure... I know the A2 wheels are for the standard Bushmaster XM15. The A4 wheels are for the Bushmaster A3 DCH, and are advertised as being 1/2 MOA.
I think the Tapco rear wheels are based on a 1/4 MOA NM thread pitch  because there are more threads per inch on the rear sight base versus the 1/2 MOA A4 base.
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Posted: 7/15/2005 7:34:02 PM EDT
[#22]
The Tapco carry handles are made in China by Leapers inc., so they do not match the standard thread pitch used on US made Milspec sight parts.
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Posted: 7/16/2005 7:05:11 AM EDT
[#23]
tag
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Posted: 8/11/2005 4:53:15 AM EDT
[#24]
tag
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Posted: 8/11/2005 5:03:52 AM EDT
[#25]
Further PROOF that ARs should ONLY be worked on at the ARMORY!!! DAMN IT!!!
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Posted: 8/12/2005 2:19:52 PM EDT
[#26]
Please bear with me here: I ordered a RRA Standard A2 20" upper, so if I want to order some NM sights for them I just need to be sure that they are A2, right? I'm new and I don't know what A4 is. Any recommendations?
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Posted: 8/13/2005 6:21:15 PM EDT
[#27]
I believe you can just get the entire NM rear sight base for about $100, and pick out a NM front post ($10-$20). With the entire NM base, you won't have to worry about thread pitch and what not because it's a complete package. |
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Posted: 9/27/2005 9:22:23 PM EDT
[#28]
Riddle me this.
I purchased a DPMS rear fixed BUIS. It has the 6/3 drum, but it will not even turn to the "5" position, let alone all the way to "6". It stops turning one click (about) shy of the "5" position. What gives? Eric |
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Posted: 9/28/2005 5:12:37 AM EDT
[#29]
When I was young and dumb like many here, I bought a NON-Colt upper assembly from one of the many AR hacks that are out there.
I ended up having the rear sight housing replaced by KEN at S.A.W. I didn't even realize that it was junk. I just remember his reaction when he saw it! "Wow! This thing isn't even Mil spec." There's a lot of SHIT out there, Kids! 
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Posted: 9/28/2005 6:45:35 PM EDT
[#30]
I've seen this in a lot of lesser sight assemblies. The slot in the sight base was not milled long enough. |
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Posted: 10/6/2005 8:21:32 PM EDT
[#31]
Wuss! |
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Posted: 10/23/2005 10:33:23 PM EDT
[#32]
any idea on the handle I have? It's marked with an "E A" on the right side.
Thanks, Jim |
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Posted: 10/31/2005 2:14:57 PM EDT
[#33]
There are also 1/3 MOA NM bases. My Accuracy Speaks NM base has the option of 1/4 MOA or 1/2 MOA elevations. The Bob Jones sight I use has 1/2 MOA windage, so I use the 1/2 MOA elevations to match. Some match shooters mix, and may use 1/2 for elevations and 1/4 for windage. |
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Posted: 11/16/2005 3:11:52 AM EDT
[#34]
yes, and the A4 uses half that, the M4 slightly more than half. the difference between the 1/2MOA and 1/4MOA NM sights is the number of detents cut into the elevation index, there are twice as many on the 1/4MOA wheel. the thread on the A2 in mongo's pic appears to be 180 out as the topmost thread is to the front. |
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Posted: 3/15/2006 3:43:16 AM EDT
[#35]
I have two DPMS DCHs and both can only turn to exactly "5". I have read some other reports that DPMS DCHs all turn to "5", including their rear BUIS.
How much milling is required to allow the sight to rotate to 6/3? It doesn't look like there's much material left in the rear sight base threads. Why does it have that slot anyhow? Couldn't they just allow full elevation adjustment w/o a stop in place? Or is it to prevent crushing the spring? |
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Posted: 4/28/2006 7:26:29 AM EDT
[#36]
Tag.
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Posted: 4/28/2006 10:15:28 AM EDT
[#37]
The Military (not NM) "A2" rear sight adjustments are:
1 'click' Elevation = 1 3/8" at 100 yards 1 'click' Windage = 1/2" at 100 yards The front sight adjustment is: 1 'click' up or down = 1.25" at 100 yards Per FM 3-22.9 Although in practice, most everyone will round the rear sight adjustment down to 1" per click at 100 yards. Which is not quite right, but will work as a ballpark adjustment. 1 MOA is 1" (1.047) at 100 yards. |
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Posted: 5/29/2006 9:43:48 PM EDT
[#38]
Bump because this has some good info and pictures. I found it very worthwhile. Stumbled accrossed it while google searching info about national match sights.
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Posted: 6/20/2006 9:34:04 AM EDT
[#39]
Update: DPMS uses custom 1 MOA rear sight bases (translation: A2 sight bases but shorter to fit the flat top upper) on their detachable rear sights, and the detachable carry handle. They use a 6/3 index wheel which is NOT the correct index wheel to use with a 1 MOA thread pitch!!  Using their screwed up combination, if you set it to "5", you are in fact setting it to about 650m-700m! In addition, using the IBZ you would be incorrectly setting it to -4 clicks from 6/3.The solution is to return the sight, get a real Colt or Bushmaster sight, or swap the 6/3 index for a 8/3 index. In essence, your Detachable carry handle is now an A2 sight but with limited elevation (maxes out just a few clicks shy of "700m"). With the 8/3 index wheel, I verified my settings using trigonometry, ballistics trajectory for M855, and the values given in the FM 3-22.9 BTW I bought my DPMS DCH's from Brownells, a very reputable vendor. It's not Brownell's fault that DPMS chose some wacky combination for the rear sight. According to DPMS, they are considering switching to the CORRECT sight base in the future, but current DPMS detachable carry handle or BUIS owners are SOL for replacements. In the meantime, avoid their rear sights unless you want to buy a 8/3 index wheel and do some part swapping. |
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Posted: 9/8/2006 8:05:55 PM EDT
[#40]
[mongo, i am getting closer! i have an a2 carbine and an a2 rifle. i am new to the ar 15 and i found the info on sight in procedures. but both of my rear sights have the 8/3 settings. but they are not calibrated i do not think. i am told to bottom out the rear sight, then raise it 3 clicks, remove the set screw so that i can adjust the number settings, and set the 8/3 setting at the line. then replace the set screw. would this be correct? and if so, would it be the same for the carbine as it would the rifle. i am really having a tough time getting this information, and i would appreciate any help you could offer . thanks, joboch .
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Posted: 9/9/2006 4:13:13 AM EDT
[#41]
I've heard two clicks then reset, but the difference wouldn't matter. It shouldn't matter between rifle and carbine either, as far as I know.
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Posted: 9/11/2006 7:24:19 AM EDT
[#42]
I recommend the Improved Battesight Zero method curtesy of Forest. It shows the procedure for adjusting the set screw as well.
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Posted: 9/11/2006 8:03:37 AM EDT
[#43]
Actually the difference between a carbine and rifle sight radius does have an effect on the adjustments, but not significantly enough that you need to change the IBZ method. The biggest thing is how to set the initial 0-200m setting and it is largely dependent on the thread pitch of the elevation sight base. 1 MOA = 2 clicks (A2, worm gear style thread pitch) 1/2 MOA = 4 clicks (finer threads, usually used with 6/3 index wheels, NM/A3/A4). I'm not entirely sure about 1/4 MOA, but I suspect that if you do have a 1/4 MOA NM sight base, it will have a special NM elevation index as well. By clicks, I mean the number of clicks it takes to go from fully bottomed out, to the 8/3 or 6/3 mark (300m). |
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Posted: 9/11/2006 8:47:40 AM EDT
[#44]
Aided by the fact that the larger angle changes of the shorter radius clicks are offset by more drop from the shorter barrel's reduced velocity, roughly cancelling each other out. Most sights are shipped set to bottom out at 8/3 (6/3) and the Army procedure is supposed to give a 300m zero at that setting, but really zeroes much farther out so the mid-range height is high enough to miss at shorter ranges. The Marines use a different procedure that really does give a 300m zero, but that's still pretty high at shorter ranges. The IBZ is a 200m zero that gives a flatter trajectory out to about 250m, which is more useful for most battesight conditions. In order to keep the 8/3 (6/3) setting at 300m it's necessary to adjust the wheel to bottom out "below" that at 200m. Most A2 sights have 3 clicks between 3 and 4 and use 2 clicks below 8/3 for 200m. A4 type sights have 6 clicks between 3 and 4 and use 4 clicks below 6/3 for 200m. IIRC the A2 is ~1 MOA clicks and the A4 is ~1/2 MOA clicks, and both use ~1/2 MOA windage clicks. Any of the "NM" sights would have finer clicks, and the wheel is marked for counting clicks, not for distance, and the competitor would have a cheat sheet of what settings to use for the specific competition distances. |
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Posted: 9/11/2006 8:56:16 AM EDT
[#45]
I did the math at one point and the shorter barrel / lower velocity does not really cancel it out. I accounted for the different bullet drops, sight radii, etc... I found that the longer barreled rifles will be off at further ranges using the IBZ with a non-standard length barrel (18", 24", etc...) While your description of the clicks is accurate, it can be misleading when the vendor choses to use the wrong parts. Case in point: DPMS used 1 MOA rear sight bases on all of their detachable rear sights, but used 6/3 indexes (designed for 1/2 MOA, or "A3/A4 DCHs"). There were 6 clicks between 3 and 4 but that does not mean to set it 4 clicks below 6/3 for 200m! I removed the sight base after wonderng why it would NOT click over "5" when IBZ'd. I realized the thread pitch was 1 MOA (A2). The solution was to either swap out the sight base or get a 8/3 index. So right now, my DPMS DCHs have 8/3 indices with the IBZ. It maxes out at 1 click below "7"  I asked DPMS about this and they said they are now working on using 1/2 MOA sight bases with the 6/3 indices for their DCHs  Executive summary: 1 MOA thread pitch (A2, worm-gear style thread pitch) = IBZ requires bottoming out at 2 clicks below 8/3 1/2 MOA thread pitch (A3/A4 DCH, some NM, fine thread pitch) = IBZ requires bottoming out at 4 clicks below 6/3 1/4 MOA thread pitch (NM, finer thread pitch) = IBZ not applicable? I hope I posted accurate info, it has been a few months since I really looked into this. |
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Posted: 9/11/2006 9:42:09 AM EDT
[#46]
I did say "roughly" cancels. At least offests in opposite directions, reducing the error. In the IBZ context LTC Santose doesn't even differentiate between M193 and M855, which of course have markedly different trajectories.
I believe that was one of the parts that originally prompted this thread... I wonder why they special-made sights by cutting off a 1 MOA sight to fit in the handle instead of just using off-the-shelf handle bases? Anyway, I don't think putting a 6/3 index half on an A2 wheel would give you 6 clicks from 3 to 4. If it did give you 6 1-MOA clicks then "4" wouldn't have been anywhere close to 400m.
I think that about covers it. I suppose if you had 1/4 MOA clicks and a "distance" wheel you'd use 8 clicks below /3 to get 200m and keep the "3" right, but I'm pretty sure the 4, 5, etc. wouldn't track right so that would be pointless. |
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Posted: 9/11/2006 10:22:46 AM EDT
[#47]
The odd part was, the DPMS sight bases weren't just cut 1 MOA sight bases
 someone actually made them that way. If you chopped a regular 1 MOA base, the rollpin stop wouldn't be there as it would have been chopped off. They came with 6/3 index wheels and I got 6 clicks between 3 and 4, but I could not rotate it above "5" (first sign something was wrong, others with Bushmaster DCHs could go over 5) In reality, the "5" position (maximum "up") was really 1 click below "7" w/ the 8/3 index wheel. I used my caliper to measure the height changes with each click, compared it to the FM 3-22.9 specs (amount of change of POI with each click) etc... and came to the conclusion that I had fixed it as good as I can get. Other AR15.com members have found oddities with the DPMS detachable rear sights. ETA: With a 1/4 MOA pitch, you'd spin that sucker forever to get it to max out the elevation
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Posted: 11/7/2006 5:19:28 PM EDT
[#49]
Ok...
I too have the DPMS BUIS (I wish I had seen this thread earlier). Who'd have thought they'd (DPMS) would put out crap. Anyway. Could someone please confirm how many clicks there should be between numbers? I've decided to take the cheapo route and just mark my existing 6/3 index wheel. I am getting three clicks from 3 to 4, four clicks from 4 to 5 and five clicks from 5 to 6. Is this correct? Thanks. |
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Posted: 11/8/2006 6:16:05 AM EDT
[#50]
That's how the 8/3 wheel on my A2 works. |
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The NM elevation adjust knob and index thread onto the A4 carry handle base like they were made for it.