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Discussion Starter · #1 ·
Looking at getting my first AR within the next couple months. I've decided on the Bushy carbine (non-M4 profile). I'm going with the A3 upper, but I also want to swap the front sight out for a railed gas block and use a detachable A2 site. This way I have the option of scoping without a riser, and adding a side sling mount and a light, all the while staying with the classic look.

I have been searching high and low here and on other websites and, while I've found the gas blocks, I can't seem to find any specs on the proper height for a detach front site, to ensure proper zero. Can someone give me some specs or point me in the right direction? Thanks.
 

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It might be a better idea to get a front sight block with a flip-up front sight. That would eliminate the worry of finding a front sight that was the proper height, and you wouldnt have to worry about it comming loose at the wrong time and possibly losing it. Just my 2 cents
 

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Discussion Starter · #3 ·
Either way, don't you have to make sure you get the right height? I just really like the look of the A2 sight. Why would a detach front sight be more apt to fall of than any other railed accessory? Surely someone has some specs...
 

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I use a detach front sight on my ArmaLite, but it's made by ArmaLite, and so is the rail gasblock... I guess the height of the front sigh post will vary depending on the manufacturer of your gas block, this part could be made a little higher or lower. I don't think it's gonna be very off if it is though. I'm guessing the normal adjustment range of the front sight post should be enough to counter any variations in height on that gas block. Afterall it's pretty much universal specs on ARs.

Sorry I can't help more than that. Maybe you need an ArmaLite? :)

Alex.
 

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Discussion Starter · #5 ·
Alex, I've seen pics of your Armalite and that's exactly the setup I'm looking for. The only thing I want to do different is a multiple-rail GB, so I can mount a sling on the side, and possibly a light on the other side. I can do the A3 Bushy carbine for $869, and the GB/sight for around $100. From what I've seen, the Armalites are higher than that. Just a matter of digging around more I guess.
 

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Actually if you are going to scope the rifle with something 5X and higher you wont even see the front post at all.

I have front posts on all of 4 of my present AR's...The 3 that did not have a front post are long gone.

Just my opinion but too many QD, Flip up, gas block mounted and all the other gadgets are just an invite for Mr. Murphy.

Karsten
 

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Karsten said:
Actually if you are going to scope the rifle with something 5X and higher you wont even see the front post at all.
Really? On a flat top?

I wanted the option to put a red dot/holosight on mine since it's a carbine, so the railed gasblock was definitely a nice plus.

Alex.
 

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alexnormand said:
Really? On a flat top?

I wanted the option to put a red dot/holosight on mine since it's a carbine, so the railed gasblock was definitely a nice plus.

Alex.
With the right Red Dot, EOtech or Aimpoint (with the right mount) the front sight and a BUIS will cowitness just fine and the Dot will sit right on top of the front post....I have 2 flat tops and 1 A2 with ARMS #39A2....Trust me it works.

Karsten
 

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Discussion Starter · #10 ·
If I were going with one of the holo sights (eotech, aimpoint etc) that the iron sights remain, and back up, the optic. But I, like alex, thought that a conventional scope on a flat top might present some problems uinless you use a high mount, which I don't want to do. Interesting...

I emailed Bushmaster tech support to get some specs: here's what I found out...

Subject: Sight Heights

When Colt came out with the A3 design with the detachable carry handle they made the front and rear sights .040" higher than the sights used on A1 and A2 rifles. The front sight forging is the same but the front sight post when set for mechanical zero is even with the top of the sight ears instead of below them as the plane for the sight post is milled higher. You will notice on 20" A3 barrels there are two raised bands on the barrel under the handguards. This designates that the barrel has the front sight base with the front sight that is milled high for the front sight post. Colt parts lists have a different part number for the higher front sight base barrels and sight bases for A3 and M4 barrels.
We decided when we began to build the A3 models with detachable carry handles that we would keep the sight heights the same for all models. Our A3 handle, B.M.A.S. Flat-top Rear Sight and Rear Flip Up Sight has the same rear sight aperture height as on the A1 and A2 receivers so that all barrels with standard height front sight bases will interchange. The Mark Brown Flat Top Mount also uses this same rear sight height. Our 3 rail gas block with detachable flip up sight is the standard height.
The A.R.M.S. Swan Sleeve, # 40 Flip Up Rear Sights, Colt A3 handle and G.G. & G. have the higher rear sight aperture height. When used with standard height front sight bases the front sight post must be turned out to the .040" higher position where it is even with the top of the sight base ears for mechanical zero.
We now carry a .040" taller front sight post, part number 9349056-M for $4.95, to correct this difference.


This really didn't answer my question, so I replied and got this:

1. We carry a clamp on front sight http://www.bushmaster.com/shopping/bmas/yhm-9495.asp that fits the 3 rail gas block. From the bottom of the detachable sight to the top of the sight post when set at mechanical zero the height is 1.700" high.
2. The sight needs to be 2.230" plus or minus .020"high from the top of the barrel.

So, If I get the Bushy gas block and front sight, I should be fine. If I go with another brand, I either have to call for specs or do the trial/error thing.
 

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+ 1 what karsten said, I have a trijicon accupoint 3x-9x and my front sight (solid A2) sits right in the middle of it and I can't even see it unless I REALLY try to focus on it, and even then only in 3x. On my other AR I have an eotech with a Larue riser so the dot is in the lower 1/3. Very nice...
 

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Discussion Starter · #14 ·
Interesting...I wouldn't have guessed that. I'll still probably go with the detach sight though. And Alex, fell free to post some more pics of your rifle...maybe some with a scope mounted?
 

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Oh, I just remembered, I have a A2 detach I don't need if you want it. It's made by RRA. It'a kinda beat up but it works fine, let me know if you're interested I think I have a picture somewhere too...
 

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Karsten said:
With the right Red Dot, EOtech or Aimpoint (with the right mount) the front sight and a BUIS will cowitness just fine and the Dot will sit right on top of the front post....I have 2 flat tops and 1 A2 with ARMS #39A2....Trust me it works.

Karsten
Karsten do you have a pic showing a view down the sights showing the visibility arond the sights and the cowitness with the ARMS 39?

Im considering getting one eventually, but I want to see what it makes the sight picture look like.
 

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Discussion Starter · #17 ·
Grunt: Thanks for the offer. I think a new one from Bushmaster is around $50. I guess a picture would help, unless your offering it for free, nudge nudge...

It all depends on how long it takes to sell my truck, as to when I will get the rifle. It won't be soon enough I assure you.

Mus, somewhere on ar15.com there is an outstanding thread, under the sights/mounts/optics heading, that shows a lot of clear images through various optics, along with the BUISs. I'll try to post a link if I can find it again.
 

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I just want one of the view of standard A2 sights cowitnessed through an Aimpoint or EOTech on an ARMS 39.

Ive seen that thread and alot of the pics are becoming invalid. Great thread while it lasted though.
 
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