I wanted to get a flip up front sight for my m4a3. I spoke to Bushmaster about this and this is what I was told.
Because of the pinned muzzle brake on the barrel, you can't get the front sight off unless you cut the brake off, and then pin a new brake back on.
This means that unless I want to spend the money on having it customized, I can't change to a flip up front sight.
Is this true?
If it is, where would I go to get this work done, and what would I be looking at spending?
Yes, it's true. Cutting the current front sight unit off is no big deal really. You can do it with a Dremel tool, a few cut-off discs and a little time and care. Most gunsmiths will just clamp the barrel in a mill and cut it off that way. The charge shouldn't be too great $25 - $40 depending on the smith.
After it's off you'll have many different options of two-piece clamp on sights and gas blocks to choose from.
Another choice is to have the gunsmith leave the gas block portion on and trim the sight tower down around it. Then you can mount a clamp on forend rail like the Daniel Defense, Samson or Troy.
Hope this helps.
You can chop your gas block and add one of these YHM front sights.