Difficulty of changing gas block?

[cajunguy]

I would like to get a bushmaster O.R.C. but would like to change out the gas block to a 4 rail so I can mount a flip up front sight. How difficult would this be. I really have no experience working on guns but am pretty good with my hands.

[smoke]

The ORC appears to have a chopped sight tower. It will be held on with taper pins. These can be difficult to remove. You must find the small side of the taper pin and drive it out from that side. If you don't, you're in for a mess.

I would recommend a flip front like the new GG&G instead of what you mentioned.

[cajunguy]

What would be the easiest BUIS to install on this particular gun?

[smoke]

What would be the easiest BUIS to install on this particular gun?

Front or rear?

For the front, I'd go with the GG&G that clamps on.

For the rear, I'm partial to the ARMS #40 STD A2.

Lots of things to consider, including the type of Optic. If you're going to scope it, then you're gonna need a flip rear and a way to remove the scope in order to use the BUIS. If you use some type of Red Dot, then you need to consider co-witness and can get away with a non-flip rear. If set-up correctly, no need to remove Dot optic if it goes south.

If you're not going to scope the gun, I wouldn't get the ORC.

[BigFatDog]

Even after you remove the pins you may have some trouble. Since Bushmaster (like a lot of manufacturers) parkerizes after the front sight installation, you may need a soft mallet to "break' the parkerizing seal. Think rusted on bolt. Some are easier to remove than others.

[space_weazel]

The technical answer is.
1) Soak pins in penetrating oil
2) Push out pin holding gas tube, slide it back and pull it out completely.
3) After sitting, start driving out the pins with the barrel supported on both sides and a piece under whats left of the sight base to hold it steady, you will need an 1/8in straight shank punch, (Lowes/HD 6set for $12) start with a small hammer and work up how hard you are smacking if need be move on to a larger hammer, again step it up slowly.
4) Once they are out use a deadblow or mallet to knock it off
5) Put on new one
6) Pin or screw
7) Replace gas tube and pin