I'm doing my first build and wondering what are the benefits/draw-backs of the standard front sight?

I imagine you would want a flip down sight with a magnified optic but I see some people with the A2 front sight AND an optic.. what gives?

Thanks for any feedback...

Cost was my reason (and I just plain like the look of an AR with one ). My FSB cost $45, while the low pro gas block and Troy flip up I was considering costs roughly $160 together.

I don't have an optic on my build, but my understanding is that the FSB get blurred and fades out of view when looking though the glass.

Using a magnified optic, you won't see the FSB when looking through the optic.  If you wanted to change out the FSB and install a low profile gas block you can however it is not needed.

I may be overly worried about it, but i've had a canted FSB. So, i don't trust FSBs from the factory any more. I always get either a low profile or railed gas block.  Besides, i had an Eotech. At 1X, the FSB was alwasy visible. You get used to it, but it did bother me a little.

There are lots of options. low profile, railed, built in flip up, etc.

For my National Match build i bought an Armalite clamp on FSB. Sure i have to check the screws every time i take it out, but i can be sure it is not canted.

When you need the sight to be able to take abuse, it has to be pinned. That doesn't mean a clamp on sight can't be enhanced with a small woodruff key, pins, or even a bb as a detent if you can have it installed. Once the sight is set up to be zeroed, witness marks and good workmanship will get it back on square.

Having an FSB is usually because of a number of different reasons - looks, because that really sets the tone of what the gun is. The Stoner FSB is distinctive, you know it's an M16 derivative right off, no mistake. Siighting, the FSB is up and ready 100%, no flipping or fooling around, and when cowitnessed, it's there and can be used. Optics these days are much more reliable, nonetheless, in combat, if it takes a round, is damaged, or goes down, iron sights mean you still have a working weapon. You get most of the same benefits with BUIS - but you have to keep them screwed on, flip them up, and hope they can take abuse and not shed little parts. After all, if a clamp on FSB can rotate, a BUIS smacked into an cargo hatch or jammed into a metal door frame can be broken, too.

Another reason is the FSB supports the use of a issue handguard - and a lot of us raised on them, used on issue 2MOA guns, don't see the point of quad rails on AR's. They don't do all that much in improving accuracy for the money spent - and since 2MOA performance is adequate for lethal shots on the enemy or medium game out to 500m, they won't fall down any more dead if the target circle is made smaller. Windage, bullet drop, and shooter error are much more likely.

I was finishing up my dissipator and used the Armalite clampon, works just fine. Once I can sight it in and mark it for being centered, I'll likely figure some way of fixing any potential rotation issues - like drlling it for a roll pin on the top of the barrel. Best of both worlds, rugged yet not gunsmith level difficulty when you need to work on it. What would be nice is an FSB that will clamp on .625 to .850 without difficultly, and be predrilled for pins. Seems like a nobrainer, then anyone can mount it anyway they like to suit their purposes.

Thanks for the responses. I definitely want something that can hold up to some abuse and I like the look of the A2 sight.

Next question:
I'd like to have the sight as close to the muzzle as possible to allow for a long handguard, Is the sight's placement purely a matter of which gas block system you use or is it adjustable?

Thanks again.

Big fan of FSBs on clones, however I hate canted FSBs in a sight picture. As many hours as I've run Aimpoints I much prefer flip ups. Basically, unless someone wants to have a clone I think they need to be low profile gas blocks

Canted FSB?  If from the factory...take or send it back.  

There is a trick to pinning a FSB.  You must pin one side with the appropiate sized punch.  Next, you tap in one taper or straight pin until fairly seated.  Then remove the punch and tap in the second until fairly seated.  Then, beat them both like they owe you money.  If you set one in and drive it with aimless measures, you can cant it EASILY.  You will ruin the drilled pin slots, and many people do this.

I like the FSB to be PINNED.  I'll post a few builds.  There are some good quality clamp types, and don't ask me to ID them - I have really no idea.  The set screw underneath type I don't care for.  Normally, you HAVE to drill the barrel to make it solid clamping - You can make it work.  Make a mistake drilling, and you will be peeved.  

I actually cut down ths FSB as prescribed in the tacked thread on how to cut down a FSB.  The pins are secure with no gas hole alignment issues.  Here are my examples.  All cut down FSBs have Magpul MBUS sights for backup, but I have holographic reddots on two, a Vortex Sparc on one, and the GRSC scope on another.  The GSRC model....I'm thinking of getting a another Sparc for lightness/capability.





I totally agree with the above comment...I have a 1-4 GRSC scope, and it does not show the FSB.  The Reddots are co-witness, so not distracting.  Good thing....Battery dead...You can still look through the reddot at the sights....Only need to buy one MBUIS or MBUS.These are all finished, and I need to take some finished pictures.  




This last one I just built for a friend.  He decided he wanted to leave the A2 sight with a free float - It's actually pretty cool looking.  He already has a Vortex Sparc on order.

For the most part the front sight is integral to the gas system and as such its placement is somewhat standardized.  There are however front sights that you can mount further out on the barrel presuming you also have a low profile gas block installed to cycle the action at the gas port location.



 

A pinned mil-spec FSB is about as rugged as it gets. Optics are subject to a variety of failures.
Some people find a fixed FSB very annoying with optics. I don’t, never the less my current goto AR has folding BUISs. Admittedly in the unlikely event of both sights failing the worst that would happen for me is cutting short a hunt.