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Page AR-15 » Optics, Mounts, and Sights
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Posted: 5/6/2003 8:09:16 AM EDT
I have opted for the OKO W sight first. I am sure I will upgrade later, but I want to check this out. I have an OLY 16" A4 with a single rail gas block. If I use the ARMS #40 BUIS, which clamp on/slip down front sight can I use, or is there a better front and back option?

I have searched and cannot find a corresponding
ARMS front sight for the #40 rear.

Link Posted: 5/6/2003 10:54:34 AM EDT
That's because ARMS sells NO front sight.

The PRI is great (I like the round hood it helps you squeeze a little more accuracy with peep sights out of the short carbine sight radius).

But the PRI requires Barrel modification to install as it has large allen screws in the place of pins.

There are many out there if the hood doesn't do it for you look around before you buy.
Link Posted: 5/6/2003 11:03:47 AM EDT
Well that's kind of what I am doing here... looking around... for input.

I think the PRI has only a barrel mounted sight, don't they? I was hoping for a front folding sight mounted to the front single rail gas block.
Link Posted: 5/6/2003 11:15:37 AM EDT
Hi Mark,  I just got a GG&G flip up modular sight put on my upper (BM A3 / 14.5 / Phantom FH) and I LOVE IT!  The only drawback is that the "ears" protecting the post get hot after firing about 100 rounds and is difficult to flip up while HOT.  It is solidly built, and thusly conducts heat.  I wanted this model as it is the ONLY BUIS set up (that I have found) that is offering a bayonet lug.  If you are going POST BAN then PRI cannot be beat, IMHO.  Check with Kurt at Kurts Kustom Firearms and see his front folding sights too.  He has excellent products and is easy to deal with.  Of course this is my $0.02!  Thanks for your time!  -William
Link Posted: 5/6/2003 11:38:07 AM EDT
How high is the Oly gas block? Best to call Oly and see what they recommend. The ARMS #40 is designed to work with a standard A1/A2 front sight. BM, Armalite and others make flip up sights to mount on weaver type gas blocks.
Link Posted: 5/6/2003 11:39:31 AM EDT
I actually have an Armalight screw on type (not flip up) and it is loose. I believe it is for standard Weaver rails, where the Oly gas blcok is Picatinny... not exactly the same size.
Link Posted: 5/8/2003 6:29:05 AM EDT
I just installed a Fulton flip-up front on an ArmaLite M1913 gas block. It puts the top of the front post at the same height as a standard A2 front. Available through Brownells or direct from Fulton Armory.
Link Posted: 5/8/2003 7:23:15 AM EDT
Bystander - I have done some measuring. The flat of the gas block rail (not in the grooves)
is 0.602 inches above the barrel and 0.285 inches BELOW the flatop receiver rail flat, as measured as best I could with my digital micrometer.

I don't know if that makes the rear flattop 'standard' being about 0.887" above the barrel, as measured just at the front of the gas block, which is just in front of the ff tubular aluminum handguard.

I am in a bit of a quandary since I have already ordered the OKO W unit and I want to
ensure that they will cowitness with the red dot.

Link Posted: 5/8/2003 12:02:51 PM EDT
Talk to Russ (sinistral rifleman) at Cav Arms. He'll be able to help you with the co-witness. I think that if you stay with a sight on the gas block that comes close to the A1/A2 front sight height you'll be OK. All the rifles I've shot with an OKO had the standard front sight.

Russ had an OKO rifle that I shot Sunday that had a pressure pad to turn it on. Not sure if I believe in that, but it saves the battery.
Link Posted: 5/8/2003 12:04:42 PM EDT
Link Posted: 5/8/2003 12:06:07 PM EDT
Lot's of pictures and a video here of Sunday's shoot. Several rifles with OKOs. I'm the tall dorky guy.

Link Posted: 5/8/2003 12:19:36 PM EDT
Wheeeeeeeeee! Man that looked like a fun way to spend a day! We don't have anywhere in this part of this big state to do stuff like that though... it is waaaaaaay to flat here.
Link Posted: 5/12/2003 3:59:20 PM EDT
I actually have an Armalight screw on type (not flip up) and it is loose. I believe it is for standard Weaver rails, where the Oly gas blcok is Picatinny... not exactly the same size.
View Quote
More likely the other way around.  

OKO should co-witness fine with the #40.  The trick will be finding a front sight that works for you.  Bushmaster makes a flip-up front sight for rail blocks, but if the Armalite doesn't fit the rail on your Oly, then it probably won't either.    Does Oly offer a sight for their rails?

AFAIK the PRI completely replaces the gas block so will require gunsmith installation.  If you're going to do that you might as well just put on a regular front sight, unless you really want the flip-up.  Or have an in-spec rail block installed so you can use your Armalite sight.
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