Is there a difference in gas blocks?

The gas block you need will depend on how you plan to attach it to the barrel. Is it gonna be clamped or pinned do you want one that's adjustable?

Some brands offer better finish, QC, or name recognition than others. Some come in different materials.

It say stick with steel, as aluminum can erode over time...may not effect function, or it may, but i dont like important gas system parts that cant operate for extended periods in the temperatures and pressures involved in burning gunpowder. Just personal preference. As for brand, get one you trust. I like Troy, BCM, YHM, etc...

These are excellent quality at VERY fair prices, I've used several of them: http://www.bte-usa.com/#!bte-set-screw-micro-gas-blocks/c110e

i normally use a steel generic gas block (low profile) from Brownells and they have served well through many thousands of rounds of ammo. I also used one aluminum block that has given no trouble after roughly 500 rounds but i did notice the set screws are now welded to the block so i better not plan to change this carbine around without realizing i would need to cut the block off.

I've had luck with aluminum blocks, but I'm not shooting full auto or even high volume semi auto fire. I've found aluminum blocks as cheap as $4.99 on Amazon, and while they may be of questionable quality, if one does fail, it's cheap enough to replace. For my pair of "fighting" ARs, my HD carbine and my future SBR, I'm running steel. Currently, the only one sporting an aluminum block is my lightweight. I have an extra in my parts box just in case.

You can get a good troy or bcm for 30 to 40 dollars for a set screw style. You might need to dimple the barrel for the set screw. You can get a clamp on stlye for about 15 dollars more.

I prefer clamped to set screw, and have found that the YHM low-pro clamp gas block is one of the few that will fit under a MI SSII handguard.

http://www.midwayusa.com/product/46...ndard-barrel-0750-inside-diameter-steel-matte

Not all low-pro are low-pro enough to fit under every handguard....

If your front gas block is good and you are a little handy with a dremel or saw, you can cut yours down and keep it pinned. I have seen this done with nice results and gives you a low profile that will fit under most handguards.

Here is a link to one of many articles:
http://www.ar15.com/forums/t_3_118/566557_Cutting_Down_A_Front_Sight_Base.html

I have several and thought about that as well until I was told it is easier to just put a new undrilled FSB on then use an old one. That is usually not one part I tend to reuse.

If you're not planning to reinstall it, just cut off your front site, clean up the cut and blue/paint/cerakote.

Absolutely - in my hierarchy of preference, pinned is always better than clamped which is always better than set screw.

If you dimple the barrel properly, I'd rate set screw as being better than clamp. Besides, many of the clamp types don't fit under keymod rails.

The MAS defense steel melonite is GTG. Get two, and drill completely through one to use as a dimple drill guide tool.

clamp on

I would always advise clamp on models. They grip better than set screws, you don't have to worry about locktight melting and screws working loose. Daniel defense makes a low pro model that will fit under FF tubes.