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Posted: 10/10/2005 7:06:33 AM EDT
[#1]
Tweak, Have you actually seen this or is it information from others on the internet that came up with those results after measuring their sights? Ive not been able to find any information relating to this... This has me wanting to call everyone I know that has a DCH so I can take measurements  ETA: If you have any links that relate to this, please post them... |
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Posted: 10/10/2005 8:23:11 AM EDT
[#2]
Ok, the RSB on my Bushy DCH looks just like the one pictured above. |
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Posted: 10/10/2005 8:34:18 AM EDT
[#3]
Thanks for the help Tweak. |
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Posted: 10/10/2005 8:34:27 AM EDT
[#4]
Yes
Info came through the old mailing list several years ago, been at this a loooooong time.
NP Cliff, always happy to. |
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Posted: 10/10/2005 8:59:59 AM EDT
[#5]
On your Colt handle does it take 34 clicks to where it stops? On my Bushy handle it takes 41 clicks until it stops. I would have measured my handle but I don't own any calipers yet. |
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Posted: 10/10/2005 9:01:40 AM EDT
[#6]
To bad, being that I'm deeply involved in this DCH topic, I have to go all the way with it I'm interested in where exactly the differences lie between the two different RSB's... |
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Posted: 10/10/2005 9:07:13 AM EDT
[#7]
thread pitch and the thickness of the web where the windage scale is marked.
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Posted: 10/10/2005 9:14:26 AM EDT
[#8]
Yes...
Thanks, now I know what to look for...  |
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Posted: 10/10/2005 9:39:53 AM EDT
[#9]
Couldn't you just measure from the bottom of the carry handle flat to the top of the rear sight base shelf just above the hash marks between the ears? I thought that's where the difference was, no? Or do you have to measure to the middle of the windage screw? Or do you even have to measure, because I can see the difference in thickness of the shelf between an A2 RSB and an A3 RSB? |
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Posted: 10/10/2005 10:24:39 AM EDT
[#10]
I removed the RSB from both handles to get accurate measurements... Here is what I have found...
The bottom of the DCH to the flat under the elevation wheel measures .276" on the Bushmaster and .308" on the COLT... A difference of .032"... The RSB windage scale area measures .1835" on the Bushmaster and .1935" on the COLT... A difference of .010"... Add it all up and I have the .042" difference, sooooo, Now I know EXACTLY where the differences lie between the two DCH's! THANK YOU Tweak!!! I couldn't of done it with out you!! Now I'm going to find a couple aspirins for this headache 
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Posted: 10/10/2005 12:16:05 PM EDT
[#11]
Now all you have to do is ask yourself, why is there a difference? We know why Bushmaster's sights are shorter, but we don't know why Colt set their sights higher. I guess they are higher just to be higher, and we may never know the real reason.
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Posted: 10/10/2005 12:54:38 PM EDT
[#12]
Colt thickened up the top area of the flattop receiver because the material in that area on initial flattop models was too thin. They raised the front sight appropriately so all existing iron sights would still zero, and there wouldn't be two sets of sights out there in different dimentions. Bushy and others decided to keep the same sight plane and make shorter rear sights on flattops. At least that is how I understand it. Edited to fix quote. |
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Posted: 10/10/2005 6:43:48 PM EDT
[#13]
does anyone know if the CMT handle works?
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Posted: 10/10/2005 6:51:51 PM EDT
[#14]
They all work... Only thing is, depending on the specifications of your particular DCH and FSB, you might have to lower or raise the FSP... And if you have to raise it to the point where it runs out of threads, you'll need to replace it with the .040" taller post... |
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Posted: 10/10/2005 7:16:41 PM EDT
[#15]
well i meant does it work no problems with the govt flat top upper. i have the BCM 20" Govt profile upper, it has the "F" FSB.
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Posted: 10/10/2005 7:38:34 PM EDT
[#16]
I have no idea what the specs are for a CMT DCH... An easy way for you to find out is to go shoot it and see... If the barrel has a true MilSpec "F" marked FSB, then the worst case scenario would be, you'll need to lower the FSP... You can measure it to find out if it is a MilSpec or commercial DCH, that will give you an idea of where your at... You could use the specs listed below to get an idea of what type DCH you have... Commercial DCH: bottom of DCH to center of windage screw = 1.006" MilSpec DCH: bottom of DCH to center of windage screw = 1.051" Commercial DCH: bottom of DCH to aperture (Bottom inside of large hole) = 1.247" MilSpec DCH: bottom of DCH to aperture (Bottom inside of large hole) = 1.292" Which ever you come closest to when comparing your measurements to the above specs should tell all... If you are wanting to purchase a new DCH from CMT, ask the dealer your purchasing it from if it is MilSpec or Commercial... MilSpec is what you want if your FSB is "F" marked... |
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Posted: 10/10/2005 8:03:20 PM EDT
[#17]
I added your post to the flattop heights thread, hoping that by spreading the info around it won't get lost so easily. |
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Posted: 10/11/2005 10:45:20 AM EDT
[#18]
Lot's of good info here.
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Posted: 10/11/2005 6:21:28 PM EDT
[#19]
hmmm
An interesting situation, that might be of some use to this thread.www.ar15.com/forums/topic.html?b=3&f=12&t=252845 |
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Posted: 10/11/2005 6:48:31 PM EDT
[#20]
Tag
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Posted: 10/11/2005 7:21:51 PM EDT
[#21]
+1..........except mine is RRA with a cardinal forge mark. I measured .8335" and 1.293" on those measurements, so that's about as close as you can get. This is proves why I need the .040" taller front site post on my 20" RRA A4. WIZZO |
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Posted: 10/11/2005 11:27:36 PM EDT
[#22]
What about PRI flipup? Is it regular or F height?
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Posted: 10/12/2005 7:38:58 AM EDT
[#23]
Tag for late night calipering.
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Posted: 10/12/2005 8:24:35 AM EDT
[#24]
PRI flip-up is probably "F" height, since it's intended for military rifles that would presumably be using the Colt/Mil rears.
WIZZO, that's very interesting that your RRA handle is mil-spec height since AFAIK RRA is not using "F" front sight bases. I wonder if that's a recent change? I got a RRA upper about a year and a half ago and I'm using a BM handle (measured to the lower height) on it with no issues. If yours measures to mil-spec height maybe the guy who told NapeSticksToKids that the RRA is mil-spec was right after all... But if RRA is selling higher handles now and still using the old FSBs then they're probably getting a bunch of calls about rifles that won't zero. |
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Posted: 10/12/2005 9:13:17 AM EDT
[#25]
This is purely speculation... Based on what I have recently discovered about the different DCH's and saying that a standard FSP measures OK, RRA sells two type DCH's, one DCH they advertise as having a A2 rear sight and the other DCH they advertise as having a NM rear sight... RRA also sells what they advertise as being a NM .050" FSP... Could these DCH's actually be milspec (advertise as NM) and commercial (advertise as A2) versions? This would explain why RRA would have to sell a taller FSP (NM .050") to compensate for the difference? |
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Posted: 10/12/2005 9:28:00 AM EDT
[#26]
Good read. Ties up alot of loose ends. I always suspected there was something different out there but didn't take the time to research it much.
Thanks to those who contributed hard data to support their claims. |
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Posted: 10/12/2005 9:34:14 AM EDT
[#27]
I believe a '.050" FSP' refers to the width. The standard A2 FSP is .072" wide. I believe .050" wide is commonly used by HighPower shooters, though the "match" sight makers offer many other widths as well. I don't know what a .028" post would be. I think that would be too narrow, even for the match shooters. Maybe they meant 0.28" tall?
As far as NM vs A2 DCHs, that would refer to the rear sight base and specifically to the threads for the elevation adjust and the markings of the wheel. I can't think of any reason for RRA to mill the main part of the handle differently for them. My guess on the height WIZZO measured is that they've switched to a different outside source for them and the new source is using the mil-spec height instead of the civvy-spec height. RRA probably doesn't even know they're the "wrong" height. I haven't been paying enough attention--has there been a surge in threads about RRAs that won't zero lately? |
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Posted: 10/12/2005 10:29:28 AM EDT
[#28]
Mike_L, Im not to familiar with the NM parts so thats why Im speculating... I couldnt find any specs to confirm that the RRA post was .050" wide, or taller post... Thanks for the NM info...
I meant to type .280" while writing my last post, not .028"... (I had actually made two errors there)...  (The correct height for a standard FSB is actually .300")I would imagine then if its a .050" wide post, the RRA NM DCH would have the different size aperture along with a different adjustment post thread pitch... That would explain the difference between the RRA A2 and NM DCH's... 
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Posted: 10/12/2005 10:37:08 AM EDT
[#29]
I agree, now that you straightened out the NM differences for me...
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Posted: 10/12/2005 11:01:24 AM EDT
[#30]
I got the handle a year ago (almost exactly) off Robert from RB Precision. I actually had to wait 2 weeks for it to be finished, but I did pay for a RRA handle. From what I can tell, it has the standard (non-NM) threads. It also has the standard 6/3 z markings on the elevation dial.
I'm willing to bet that if I threw this on my mid-length upper that has a Sabre Defence barrel ("F" FSB), it would zero correctly, unlike my current situation. WIZZO |
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Posted: 10/12/2005 12:28:23 PM EDT
[#31]
i thought i'd throw a wrench in the gears, so here goes
i have a Colt R0901 complete upper. it had a standard a2 FSB (not the F version) the carry handle was MMA forge code. funny thing was it measured 0.780" from the bottow to the top of the shelf cutout. so i guess my point is that colt made them as well? just as a reference: i took out my 6920 upper's carry handle and it measured the 0.833" as previously posted |
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Posted: 10/12/2005 1:06:32 PM EDT
[#32]
Sounds like your 901 upper is an old one. The MMA forge code was used in the early 1990's before the flat top was standardized in 1995 by the US Army. Also barrels used on flat tops during this time frame did not have the F stamp, were not dated stamped by the FSB, and not until 1994 did they stamp the O on top of the chamber. Friend of mine has an early 6700 with a no F stamp FSB, and a MMA forge code carry handle, will measure that carry handle next time I am at his place. |
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Posted: 10/12/2005 1:06:54 PM EDT
[#33]
Yup, looks like COLT used both size DCH's too... |
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Posted: 10/12/2005 1:13:05 PM EDT
[#34]
i picked it up from D. todd over on subguns. i don't know how i could determine its age though
my guess is it had been sitting for a while, most of the preservative oil had dried up. shoots just fine though. |
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Posted: 10/12/2005 1:13:58 PM EDT
[#35]
LOL... Sounds like me now, I take my digital caliper with me when visiting friends that have AR's with DCH"s...
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Posted: 10/12/2005 1:27:27 PM EDT
[#36]
Got my upper from Dennis also. The barrel is not hard to date, or get close anyhow. Barrels were marked with a two digit code by the front sight base, this one marked 28. This was done from about 1980 through some time in 1995:  Starting in sometime in 95 a date code is stamped by the front sight base. First two digits is the month, second two digit number is the year, this one 03/02:  Starting in 1994 or so an O is stamped by the chamber (some look like C’s) indicating a chromed chamber/bore:  Beginning in the late 90’s a paint mark is added in front and under the barrel nut, not sure of it’s meaning:  So, let us know what you markings are, then we can get an idea of the date. My guess is that yours is a 1992-94 upper, and that is why it does not have a F FSB, and why it has the short DCH. |
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Posted: 10/12/2005 1:29:15 PM EDT
[#37]
Yeah, I do stuff like that quite a bit. Last gun show down here I borrowed a barrel from CMMG just so I could take it outside and shoot pictures of the markings. |
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Posted: 10/12/2005 1:40:31 PM EDT
[#38]
the shorter handles were the original version. since the cloners pick up COLT's table scraps that's why we're still encountering them. |
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Posted: 10/12/2005 1:52:14 PM EDT
[#39]
mine has a "29" up front by the handguard cap the "O" is present but it is a the 12 o clock postion ( directly below gas tube) with a double triangle stamped (lookes like a double stamp because the second triangle is not as deep as the first) about 1/2" forward of the "O" towards the muzzle. no white paint marks. |
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Posted: 10/12/2005 1:57:22 PM EDT
[#40]
That is 1994. Very interesting, and thanks for checking all that out. |
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Posted: 10/12/2005 2:16:14 PM EDT
[#41]
Wow, glad to see that this thread has neared its end with some great information. Thanks guys.
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Posted: 10/12/2005 3:17:37 PM EDT
[#42]
That makes allot of sense... Now I understand why the shorter handles are on the early COLTS and still found today on the newer clones... 
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Posted: 10/12/2005 4:13:16 PM EDT
[#43]
What i don't understand is why they went with the taller "F" marked FSB and the taller shelves on the DCH at all. As opposed to just keeping the shorter carry handles and the standard a2 sight block. |
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Posted: 10/12/2005 4:20:29 PM EDT
[#44]
So is the taller front and rear sight a Colt thing or a military thing? Whoever it was, why would they want to confuse things by doing that?
I need to hear a real good reason for the existence and use of taller FSBs and DCHs. Right now, to me, it seems like Bushmaster did the smarter thing by going with the standard FSB and the shorter DCHs. If most all of the BUIS out there copied the standard sight height instead of copying the taller sight height, what would be the reason for the taller sights? |
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Posted: 10/12/2005 4:27:43 PM EDT
[#45]
+1 I called Colt and they couldn't even say why, I don't even think they knew. |
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Posted: 10/12/2005 6:23:02 PM EDT
[#46]
For reference, the YHM front and rear BUIS are the .040 higher version.
I have a YHM rear BUIS and it needed the .040 taller front sight for use with the standard FSB. I later added a YHM front flip sight which came with a standard height sight installed and it zeros with the rear sight perfectly. |
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Posted: 10/12/2005 6:32:31 PM EDT
[#47]
last time i looked at this thread, it was 2 pages. I'm not going to go back and read through arguing. So, I'll just ask, did anyone suggest that maybe Colt tried to throw other companies off by making a few minor changes when they introduced the flattop M4?
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Posted: 10/12/2005 6:38:57 PM EDT
[#48]
Again, according to a link posted earlier, the initial flattop models had *very* thin material at the top under the rails (apparently enough to push a pencil through? would like to know more about this story). Colt thickened the area which raised the rails. They chose to raise the front sight so existing rear iron sights would still zero. Their plan worked perfectly until all the meddling kids came around and decided not to use the "F" FSB on flattops... And of course, I may be wrong, but that's how I understand it. |
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Posted: 10/12/2005 7:33:11 PM EDT
[#49]
1982:
At Picatinny, Vince De Siena and Major Dave Lutz (USMC) machine off the carrying handle of a M16A1 upper receiver, affix a commercial Weaver scope rail, and then mount a Kahles 1.5x optic. MAJ Lutz begins shopping the idea around a possible addition to the list of features for the M16A1(PIP). (Lutz also believes that this prototype may have been the genesis of the later Canadian flat top project, due to his sharing an office with the Canadian Army Liaison Officer to JSSAP, Major Rick Wilson.) August 1989: Richard Swan of A.R.M.S., Inc. is shipped a sample of the Colt ACR's upper receiver and forging along with a purchase order for reengineering the upper receiver's scope rail. One of the main goals is to increase the strength the rail, as the existing rails cuts make the receiver too thin. (Reportedly, Swan demonstrated to Colt's Robert Roy that he could pierce the receiver at the bottom of the cut using the point of a Number 2 pencil.) August 1990: Colt and A.R.M.S., Inc. sign a non-disclosure agreement relating to their improved flat-top rail design. Oddly, the final design does not match the dimensions of Swan's earlier rail designed for the Canadians. 1992: Colt commercially introduces their flat-top receiver for rifles and carbines. These are commercially designated the M16A3 and M4A1 respectively. (However, these weapon's features should not be confused with those of the military type-classified weapons using the same designation.) August 1994: The US Army officially adopts the M4 and M4A1 Carbines. Colt is awarded ~$11 million for 24,000 carbines. Only the first lot of M4 will be delivered with fixed carrying handles. Afterwards, all M4/M4A1 in inventory will be shipped with flat-top upper receivers. February 1995: MIL-STD-1913 is approved, providing a standard for accessory/scope rail dimensions. |
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Posted: 10/12/2005 7:45:12 PM EDT
[#50]
I hope so, been saying since '98
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