Which BUS do I need

[Dfresh15]

I have the M&P15 OR model and I'm looking to add some BUIS. Since the Rail and the Gas Block are the same height, don't I need a certain type of sight? I can't just buy any pair can I? I'm looking at the Troy Sights or if you suggest any other decent Metal BUIS that doesn't cost as much. Thanks

 

[78Staff]

I have the M&P15 OR model and I'm looking to add some BUIS. Since the Rail and the Gas Block are the same height, don't I need a certain type of sight? I can't just buy any pair can I? I'm looking at the Troy Sights or if you suggest any other decent Metal BUIS that doesn't cost as much. Thanks

You don't need anything special, just standard Metal BUIS, like the Troys you mentioned would work fine. Troy's are often mentioned as being pricey, but realistically they are one of the middle-cost metal folding sights available from a known brand - ie take a look at KAC, Dueck Defense, GG&G, and others .

That being said, Magpul has a nice set of metal folders out (Pros), a bit slimmer profile than the Troy's - they are typically in the $150 range for the set.

Spikes Tactical also has a set of metal folding buis, not sure on price but they are are built to be slimmer as well I think.

I run a set of Troy's, KAC Micro's, Magpul Pro, and DD Fixed on different rifles. Matech is also a nice rear sight if you are running an A2 post style front sight or any fixed front - the Army uses a ton of them. USMC uses the KAC mostly. Reality is they all do what they need to do, just depends on which one you like.

The Troy opens with the large aperture by default, most open with the small by default - so that is something to consider, if you prefer one over the other. Some folks hate shooting large aperture.

The Troys also lock up, while the other flip up and snap firmly into place, but do not lock. On the one hand, locked up sights will never get folded down accidentally. On the other hand, sights w/o a lock can fold down when hitting obstructions, which may prevent damage in the field.

Troys will run about 180 online, $200-220 in local stores. Magpul Pro's run about $150 online, so you can save a few dollars there and they are a fine set of sights. They are also tooless, which is nice. Actually I guess they all are tool-less, but the Magpul Pro (and KAC) front is very easy to adjust, no bullet tip or sight tool required.

 

[cyphertext]

You need for them to be "same plane" or "rail-mount" height. Most sights are of this nature.

If they state that they are made for mounting on a gas block, they most likely will not work on your rifle... While the 15 OR has a railed gas block, the rail is at the same height as the receiver rail. Many railed gas blocks are lower than the receiver rail height and will require a taller front sight to make up for the difference.

 

[Kadonny]

Most sights should fit the OR. That's how they make them, compliant to most AR rifles.

 

[Dfresh15]

You need for them to be "same plane" or "rail-mount" height. Most sights are of this nature.

If they state that they are made for mounting on a gas block, they most likely will not work on your rifle... While the 15 OR has a railed gas block, the rail is at the same height as the receiver rail. Many railed gas blocks are lower than the receiver rail height and will require a taller front sight to make up for the difference.

Thanks cypher. That's what I thought. That I need to buy Same Plane sights. Thanks

 

[78Staff]

Same Plane would be considered "normal" sights by most - its gas block height sight that would be considered different, dimension-ally speaking... and will... well should say so in the description.

 

[cyphertext]

Same Plane would be considered "normal" sights by most - its gas block height sight that would be considered different, dimension-ally speaking... and will... well should say so in the description.

But the confusion comes in with the 15OR, since the railed gas block is not the "normal" height for a railed gas block... It is good to know exactly what you are looking for.

 

[78Staff]

But the confusion comes in with the 15OR, since the railed gas block is not the "normal" height for a railed gas block... It is good to know exactly what you are looking for.

Yep that's what I recommended in my original post .

 

[cyphertext]

Yep that's what I recommended in my original post .

I'm not saying you gave bad info in the first post, but you just said that he doesn't "need anything special". When you go look at Troy's sight, you really don't get an indication that the "gas block" sights are special, or outside of the norm... That is why I differentiated between the two, to try to make it a little clearer for the OP. Many people have bought the gas block sights because they were mounting them on a gas block... seems to be logical.


Your pic clarified it even further, showing the height difference that I referenced.

When I first got my .22lr AR, I did the exact opposite. I bought Magpul sights and put them on my son's 15-22, and took his sights and put them on my new rifle... couldn't sight it in because the front sight was mounted on a "gas block" on my rifle, and I didn't notice that there was a height difference.

 

[Kadonny]

Yeah the OR is different than other gas block mounting heights, but it does make it a bit easier to get sights since you can choose any same plane sight.