Low-pro gas blocks vs block w/intergral flip-up sights

[sir_n0thing]

Hey all... so I'm about 30% into my first AR-15 build (I am new to the AR, but not new to firearms) and one item that is causing me much indecision is which way to go with the gas block.
On one hand I thought about going with a low profile block and put a flip up front sight on the rail.
On the other hand I have looked at items such as the YHM block that incorporates a flip-up sight (http://www.midwayusa.com/viewProduct/default.aspx?productNumber=257276).
I've search here and all over google looking for opinions, but haven't managed to turn up a whole lot. Are there any real advantages or disadvantages between the two options? Obviously the choice made here could effect the rail length, but are there other considerations I am unaware of?
Some general info about this build... I picked up a stripped Spikes lower and a stripped YHM upper. I installed a Palmetto LPK with the MOE grip. I have a BCM buffer tube assembly coming. All other parts are still in the planning stages.
I am tentatively planning for a 18" barrel with rifle-length gas system. Hand guard/rail system to be determined. I will be running optics of some sort (undecided at this point) but want flip-up irons for back up.

Thanks in advance for any info!

[Eric D.]

If going low-pro I would prefer the gas block be covered by the rail, especially if its not pinned. I would also stay away from the gas block/flip up combos because if the sight breaks, its that much more of a bitch to replace.

[Quiet-Matt]

I recommend staying away from the YHM sight. I tried one i the past and they had 2 problems that I found. First is the pivot pin isn't captive and will walk out. I fixed this by staking the holes on either side. The other problem was that it is a two piece clamp-on design and the 4 screws need to be checked periodically for loosening. I fixed this by adding tiny stainless split lock washers.... Then I sold it and re-installed the front sight tower that came on the barrel. It is the only way to go (in my opinion) if you want a front sight that is mounted to the barrel. This should be fine for your application with a rifle length gas system. Plenty of reach, and with a scope over 2x you won't even notice it.

If you want a free float rail, go with the shaved front sight tower or a pinned low profile gas block. Screws are un-acceptable IMHO, on a serious use weapon, without staking or welding to ensure that they stay put.

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[Ando]

I've got a couple of YHM flip ups and generally I like them, but I do recommend a high temp loctite on the screws. I consider them a back up site for scoped rifles and I have been reluctant to put them on hard use rifles. A better though more expensive option would be the PRI flip up.

[kartoffel]

Front sight on the barrel is superior to front sight on the handguard, because the point of impact won't shift.

However, any gas block that's not protected under a handguard really needs to be pinned. KAC gas blocks can be pinned. The VLTOR set screw ones can also be drilled and reamed for taper pins. Neither will fit in a standard FSB pinning jig; so you'll have to rig your own fixture. Cerrocast would be my choice. Good luck :)

[polydeuces]

The one YHM flip-up I have is fine. Gets banged around and does not move. Put it on and tighten - really really tight!
1 yr of use and counting. But considering what others are posting - who knows, there may be an occasional weak spot.
Keep in mind - it is BUIS - so as such I only flip it up on occasion stay in practice with iron sights.
Give it a try, if you don''t like it take it off - no problem. You can always put on the low profile gas-block.

[sir_n0thing]

Thanks for the insight.
Though I intend on going with optics and the sights will be purely for back-up in case of optics failure, I do want them to be as reliable as possible.
Since I am building a rifle-length system, I doubt the gas block will be covered by the rail so low-profile is not "critical". I can do either a block with flip-up sight or a block with rail top and mount a flip-up on that.