All,
My Googlefu is weak today :sos: and I am having a hard time finding a good quality detachable carry handle with the 8/3 adjustments. I have ordered and received a Bravo Company Mfg. 20" government profiled upper for my wife and am in need of a detachable carry handle rear sight for it. I have searched the usual sights of RRA, BMC, DPMS, Brownells, Midway etc. and I have yet to find one that is of good quality (per reviews) and that is definately calibrated with the 8/3 setting. Any leads would be much appreciated.
Thanks.
DryFire
So with further research I have learned that the A4 style of receiver with detachable carry handle will not permit the 8/3 elevation screw to be used due to length issues. I guess this post is pointless, sorry to all. :wb:
DryFire
Quote from: DryFire on December 12, 2009, 10:39:00 AM
So with further research I have learned that the A4 style of receiver with detachable carry handle will not permit the 8/3 elevation screw to be used due to length issues. I guess this post is pointless, sorry to all. :wb:
DryFire
I'd check further into that. I have a RRA A4 NM rifle with a detachable carry handle that has those sights. Bought the rifle the first year they became legal for service rifle matches.
Give RRA a call and tell them you need a cary handle for an NM(National Match) A4.
http://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_id=226 (http://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_id=226)
Hmm might just have to do that, sadly RRA is one of the more costly detachable carry handles, but for the wife I really have been trying to buy some of the best I can. I already have a RRA Lower Parts Kit with the 2 stage trigger on order for this project, hmmmm. Thanks.
DryFire
My experience has been that the 6/3 works. The difference between the 8/3 and the 6/3 is that the 6/3 clicks in .5 MOA. If you want to shoot beyond 600 just count clicks.
Oh, and while zeroing... zero at 25M on the 6/3 + 2 (clicks) setting. brought back down to "6/3" one will be on at 33M and 300M.
Check out my friends at Armalite:
* http://www.armalite.com/ItemForm.aspx?item=10806400 (http://*%20http://www.armalite.com/ItemForm.aspx?item=10806400)
* http://www.armalite.com/ItemForm.aspx?item=E20220 (http://* %20http://www.armalite.com/ItemForm.aspx?item=E20220)
I'm shooting the moon with this one...
But couldn't you just buy the rear-sight parts and swap 'em out?
Ok so I am still looking at all of this and I am begining to think that perhaps I am asking the wrong question. I guess what I really should be asking is what is the difference between a 6/3 and 8/3 knob. I know that on the 8/3 when the base is at its lowest it is at the 3 or 300 meter setting and then when rotated one full turn it is on the 8 or 800 meter setting. I would then assume that the same is true for the 6/3, that being 300 meters and then 600 meters. My question then becomes since a full turn with both rear elevation drums results in a 200 meter difference is this simply a result of the different barrel lengths between the M4 and A2 style rifles? Or on the other hand are the elevation wheels and coresponding sight bases machined with a different thread to corespond to the one full turn equals so many MOA of adjustment? I am assuming that it is simply a matter of barrel length but I could be mistaken.
DryFire
Quote from: DryFire on December 14, 2009, 08:55:27 AM
My question then becomes since a full turn with both rear elevation drums results in a 200 meter difference is this simply a result of the different barrel lengths between the M4 and A2 style rifles? Or on the other hand are the elevation wheels and coresponding sight bases machined with a different thread to corespond to the one full turn equals so many MOA of adjustment? I am assuming that it is simply a matter of barrel length but I could be mistaken.
DryFire
I'd like a definite answer to this question as well.
So, I've figured this out.
Detachable carry handles (A4 typically called A3) sights click in 1/2 MOA. Standard attached A2 sights click in 1 MOA.
The differerence in barrel length does this:
A 16" AR's bullet path will cross the line of sight in 2 places: 25M and 300M.
A 20" AR's bullet path will cross the line of sight in 2 places: 31M and 300M.
To zero a 16" for 300M, simply zero at 25m on the 6/3 setting.
To zero a 20" for 300M with a detachable carry handle (A3) sights, zero at 6/3 + 2.
To zero a 20" for 300M with an attached carry handle (A2) sights, zero at 6/3 + 1.
This is pretty much true for 55grn and 62grn mil surp as their paths are common enough out to 300.
Does this solve things, Dryfire?
My next question is this:
What about distances beyond 300m? Does a 20" 6/3 AR15 still use the indexed numbers? It wouldn't seem so.
I suppose one should zero their rifle for 300m, then find out bullet drop for their type of ammunition... then count clicks, keeping in mind that 6/3 rifles adjust in 1/2 moa and 8/3 rifles adjust in 1 moa.
The indexed numbers seem to only work for M855.
Whisker,
Somewhat, I contacted RRA about it and asked the difference. It seems that despite the clicks being 1/2 and 1 the threads and length of the rear sight posts are different. After I ordered and installed the detachable carry handle it made sense. When I take my A2 with the 8/3 setting and remove the upper 1/2 and then the charging handle and BCG I noticed that the rear sight post extends almost all the way down to the top of the carry handle. Meanwhile with the A3/A4 upper this area is not milled out and is solid. Being that this area is not milled there simply is not enough room for an 8/3 sized post to fit. I further confirmed my suspicions by getting on Numrich and looking at part numbers for the rear sight tower for both the detachable carry handles and the A2 rifles. They are indeed different part numbers. So while each one requires one full turn to move from the 300 setting to the 800 and 600 settings respectably, the rear sight tower will move by different amounts.
I pulled out my trusty Mitutoyo calipers just to see what I could come up with and here it is. When the A2 rear sight is moved from 300 to 800, or one full turn, it moves .150". On the detachable carry handle when moved from 300 to 600, also one full turn, it moves .072". One full turn results in different amounts of elevation. So just for fun I turned the A2 wheel down to the 600 setting and the movement from 300 to 600 on the A2 sight was .072". The same distance as the 300-600 change on the detachable carry handle. Armed with that knowledge I know that the hard number settings on the two wheels should be the same out to the 600 distance. Of course the clicks will still be different but the hard numbers are the same.
DryFire
So you're saying that you can use the indexed numbers for targets past 300m w/ a 20" barrel and 6/3 sights?
It seems to me like that is true, at least out to 400 m by looking at a chart in a FM. At 400m, M193 drops 14.72" below the 300m zero. That's aprox 4MOA. So an A3 would click 8 clicks.. A2 would click 4 clicks.
I'd like to know distances beyond that.
As far as the hard numbers on the wheels go and their corresponding to clicks. On my two rifles RRA Std. A2 (not NM sights) and a BCM detachable carry handle. I just picked them up and here is what I found.
A2 300-400 3 clicks
A2 400-500 4 clicks
A2 500-600 5 clicks
A4 300-400 6 clicks
A4 400-500 8 clicks
A4 500-600 10 clicks
So armed with the information that an A2 is 1 moa and the A4 is 1/2 moa then this all lines up. Taking that into consideration with the fact that when measured with a good pair of calipers the amount of movement from the 300-600 settings on both sights is the same, I would say that with both rifles possessing 20" barrels the hard number adjustments should be more than similar enough for Appleseed work :---
DryFire
I'm chiming in kinda late, now that you figured it out. If you go to the WSMR section of the forum (NOTE: Only IIT3 + allowed access- primarily meant for those who will be doing advanced training) and then to the training manuals, there you will find the sighting in procedures of A2, A4, and M4 types along with disassembled views of the sight mechanisms. All very educational and useful... Enjoy!