So I like the 14.5 inch barrel and have no problem with an A2 Flash, but why welded on? I abolutly do not want to have a flattop AR-15/6.5 Grendel 14.5 inch barrel with a fixed front site post.

The A2 is welded on so I can not take off the Front site post without sawing it off. Now even if I do that, how do I get the low rise gas block in place of the front site post? I cant slip it on over the front nor can I take the barrel off and slip it on from the rear of the barrel.


Note What ever the solution I am not doing this myself it we be done by a paid and licenced professional.

If I cut the A2 though I will not have a gas block there any more. I still need to replace with a gas block.

Edit* Are you saying that that is a gas block and sight?


I am using my Trijicon and Troy front and rear flip ups. for my 14.5 setup.

Bill, I think I chose a poor choice of words. I understand the law. What I dont understand is why they would offer a flat top rifle with a fixed front site. I am totally fine with the Flash. in fact I like the A2 looks, I just dont care to have a Fixed Front Site on this weapon system. If the Sight and Gas Block could be replaced easier that would be great!!!

Standard fixed FSB are used because they're cheap. As in, near-free. Five bucks, maybe. They're forged tens of thousands in a batch. Same as dust covers, pins, standard trigger groups, barrel nuts, and all other parts that can come directly off a production line with zero fitting required. It's the beauty of standardized, interchangable components.

So, the "good" news is that you don't have to care about cutting a FSB. They're ultimately disposable. Here are a few good solutions for you:

1) Cut the FSB completely off and use a bolt-on gas block, like the YHM units.
2) Cut the top of the FSB off, making a "low profile gas block," and install a railed forend to hold a flip-up front sight.
3) Grind the weld, extract the pin, remove the FH, and modify it any way you want. It's just a weld and it's easy enough to put back on. Heck, cut the FH if you want to, those are cheap, too. If you're doing it yourself, silver solder is an acceptable attachment method, though it's not as easily removable as a pin & weld. If you decide to cut the FH, the way to do it is to use a cutting wheel on an angle grinder and cut in from the front end, horizontally, until you break into the gas ports along either side. Take a detail cutter(Dremel works), and cut into the FH, continuing the holes you're into, around to the rear. Only cut a little bit and don't go so deep that you damage the threads on the barrel. Then you secure the barrel really well and use a cold chisel in the vents with a BFH to split the FH in two halves. Be careful not to hit the barrel crown. Then just get another $5 FH to replace it with.

ETA: Oh, and if you replace the FH, be aware that a standard A2 is ever-so-slightly too short to make a legal 16" on a true 14.5" barrel. You need an extended A2, or any number of 2" muzzle devices on the market (the threads will take up about half an inch).

Yes. Get the flip up YHM front sight/gas block. You needn't touch your flash suppressor.

1.) Place tape over your barrel at the M4 cut (to avoid knicking your barrel with the dremel later).

2.) Remove roll pin from gas tube.

3.) Drive the dowel pins (straight, not tapered) out of your current gas block.

4.) Gently tap gas block forward while pulling the gas tube loose.

5.) Move gas block forward until it is over the M4 cut in your barrel (it will give you relief to use a cut off disc in a dremel).

6.) Use dremel to cut through both rings of the gas block on one side. Spread the rings (they are soft and bend fairly easy) and remove the old block.

7.) Install bolt on YHM flip sight/gas block and you are done.

Even easier to do (if you use a little care) than typing this out on a crackberry! :D. Enjoy!

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