Aluminum gas blocks

[longslide10]

I've bought an S&W M&P flat-top rifle. The dang thing has a fixed front sight on it. Don't quite understand the logic there. I want to replace the front sight with a new gas block and a folding sight so I don't see that front post when I use the optical sight. Most of the replacement blocks I see are aluminum. Knowing that aluminum expands much faster than steel, I'm having a hard time bringing myself to go that route.

My question is: Do the aluminum gas blocks not leak hot gases and possibly erode the block when they start heating up?

Thanks.

 

[NWSharpshooter]

That front sight is the toughest sight available and does not interfere with optics in any way shape or form. I own many AR15s and I would never own one without a standard front sight base gas block unless it has a low profile block under the rail. I have used every type of optic you can think of, and prefer them with an A2 FSB.

 

[longslide10]

The post on mine is dead-center of the optic sight when I look through it. That's interference to me.

 

[NWSharpshooter]

The post on mine is dead-center of the optic sight when I look through it. That's interference to me.

If the optic is sighted in, the cross hairs or red dot will sit right on top of the sight post. This is called a cowitness and is a good thing. If your optic is magnified, the fsb will disappear under magnification. If you are using a red dot and it bothers you that much, get a higher mount to create a lower 1/3 cowitness (also a good thing). Railed gas blocks are junk and they only put them on factory uppers to save the cost of drilling and pinning a FSB gas block. Again, I would never buy an upper or gun with this setup. I don't like cut corners.


If you notice, the M4s and M16A4s the military uses with optics also have an A2 FSB gas block.

 

[longslide10]

Ahh, "co-witness". Regular or lower 1/3, it means: "see the front sight when you look through the optical sight". Is a fixed front sight more rigid than a fold-down, of course. As is a rear peep sight mounted on the handle compared to a fold-down rear sight.

But we digress.

My question was about aluminum gas blocks and you're saying all railed gas blocks are junk, aluminum or steel.

I'm afraid I fail to see your logic. Unless the OEM front sight/gas block is made from "unobtainium", there must be some aftermarket blocks that are just as good.

But again, my question is: Does anyone have any experience with the aluminum blocks and do they actually function properly and stand up to moderate use.

I suspect they do not.

 

[NWSharpshooter]

The reason they are junk has nothing to with the material they are made with and everything to do with the way they mount.


An A2 fsb is drilled and pinned to the barrel. It is very solid and almost impossible to accidentally move. Railed gas blocks are held in place by set screws. Bump the gun, drop the gun, etc. and you run the risk of knocking it out of alignment. Since the gas port and gas block have to be perfectly aligned for the rifle to cycle properly, this is a huge deal. Drop your gun and now it is a single shot. Not to mention when you drop it your optic will probably break and since you won't have good solid aligned BUIS you are double screwed.



As I said, I won't own one. If you change it out anyway, make sure you save the original fsb and pins otherwise you kill about 200 dollars of the rifles value.

 

[Laxguy59]

The reason they are junk has nothing to with the material they are made with and everything to do with the way they mount.


An A2 fsb is drilled and pinned to the barrel. It is very solid and almost impossible to accidentally move. Railed gas blocks are held in place by set screws. Bump the gun, drop the gun, etc. and you run the risk of knocking it out of alignment. Since the gas port and gas block have to be perfectly aligned for the rifle to cycle properly, this is a huge deal. Drop your gun and now it is a single shot. Not to mention when you drop it your optic will probably break and since you won't have good solid aligned BUIS you are double screwed.



As I said, I won't own one. If you change it out anyway, make sure you save the original fsb and pins otherwise you kill about 200 dollars of the rifles value.

Love you NWS but your not entirely right, it won't kill 200 from the value and there are proper ways to install a low pro.

My low pro will have small dimples drilled into the barrel and the screws loctited in.

 

[NWSharpshooter]

Love you NWS but your not entirely right, it won't kill 200 from the value and there are proper ways to install a low pro. My low pro will have small dimples drilled into the barrel and the screws loctited in.

I suppose you are right on both points. With an AR it is never hard to find someone to pay full retail or more when selling. What I should have said was I wouldn't buy one unless it was heavily discounted. As far as your second point. While drilling dimples does increase the rigidity, it still falls short of the rigidity of a properly pinned fsb. Not only that, but it is an unneeded expense as it is not necessary if you are going rail over block, and if you are not going rail over block the standard A2 fsb makes more sense. I understand the thought process of wanting the fsb out of the way on a flat top rifle. Years ago when I purchased my first flat top I wanted it gone too and truth be told spent a bunch of money getting rid of it. In the end I was unhappy with my choice as I learned more and realized that what I had to begin with was a better option, and my money gained me nothing except a less original, less versatile, less reliable gun.

 

[Laxguy59]

Yea gasblocks out of the rails that aren't fsb's are ghey, but I'm in love with these newer Ultra low profile blocks.

 

[NWSharpshooter]

Yea gasblocks out of the rails that aren't fsb's are ghey, but I'm in love with these newer Ultra low profile blocks.

My Recce and my dissy both have yhm ultra low gas blocks, but they are under the hand guards. My Bushmaster dissy has a low pro under the hand guards that is drilled and pinned as is the non functional fsb at the rifle length position. . Companies like SOTA put the railed gas blocks on their uppers as a way of cutting corners and saving manufacturing costs, not because it is better.