What's the difficulty factor regarding the replacement of the front sight/gas block?  Is it as simple as pushing out the pins, sliding off and putting another on (one with rails instead of the sight)?  Does the gas tube just push into the hole in the gas block?  I'm considering replacing the stocks with a free-float type and as mentioned, a gas block with rails instead of the tall sight, then lowering my scope.  Thanks for any information ahead of time.

Hey, thanks for the reply.  I've got the tools and am pretty handy. Where is the gas tube retaining pin?  I've been looking at all the exploded views but haven't noticed the gas tube retaining pin.  Is it in the front site assembly?  If so I haven't located it on my rifle yet. Thanks again for the info.

Charlie

Look at the base of the front site tower.  You'll see a small hole that goes through the base.  That's where gas tube pin is.  Use a 1/16" (or 1/8" I can't remember) punch to drift it out.

You might have to heat and/or soak the front gasblock and sight in Kroil or any other penetrating oil. I have had them pinned on so tight that they had to be drilled out. The pins are tapered, make sure you are hitting the smaller end to remove. Good luck. I have gas blocks with rail for sale if you need them.

Tapered?  Is there some kind of protocol to determine which is the small side?  I mean, do gunsmiths and/or factories follow a set procedure so there's a realistic expectation of getting the correct side to start with?

Panz
[bounce]

On the few Bushmaster's I've worked on, the pins were all driven in from the right (ejection port) side.  So they had to be punched out from the left.  Just take a look at the pin ends on both sides and you should be able to distinguish the difference.  If not, grab your calipers.

I agree that BM taper pins seem to be in there pretty snug.  Also, the pin holes are not always drilled in exactly the same spot vertically.  The distance between the pins seems to be consistent, but I have had to do some extra filing of the barrel to get the pins through.

I really appreciate all the information.  You guys are giving me the confidence to attack this project.  I found a great exploded view on this site somewhere that shows everything.  My rifle is a Colt so the pins may or may not be as tight as the Bushy. I'm workin' up to trying this project.
Oh by the way....what is Kroil and where do you get it?

Just be sure and REALLY support the sight base/gasblock on a VERY solid surface before you start pounding on the pins.  Use a large hammer and a drift pinch.  If the pin does not come out with the first blow then hit it much harder the next time.  Repeated light blows only flattens the end of the pin like a rivet and makes it harder to get out with each hammer blow.  Last resort is to drill them out.

I just had the same kind of problem Russ4777 described.  I had a terrible time removing the Bushmaster pins.  Here's a [url=http://www.ar15.com/forums/topic.html?b=3&f=4&t=175889]link[/url] to my experience.  I actually had to cut the damn front sight tower off the rifle.  I'm just lucky I didn't trash the barrel.  

Make sure you really brace that sight post well.

What kind of hard surface do you guys recommend?

Brownell's sells a 'bench block' that has a groove to put the barrel/sight on.  You can drill a hole where the pin needs to be punched through, and modify it so the front sight base will sit firmly in it.

[url]http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=7675&title=EXTRA-LARGE+BENCH+BLOCKS&s=19243#19243[/url]

I don't have one, or even know if it will work, but the next time I need to remove a front sight, I'll give it a try.

Awesome!  Thanks, M4-guy!

Maybe I am lucky, but I have removed a LOT of FSB of many different manuafcturers with few problems...

Rule number one is have the right tools.

Get the Brownells convex punch pin for taper pins.  This will reduce chance of marring FSB and keep the punch on awithout flattening it out.

You can use a 16-24+ ounce hammer.  A lighter weight hammer will make the job much harder.

Put maskign tape or electrical tape over the pins to further reduce the chance of the punch bouncing off taper pin and buggering up your FSB/barrel.

Knock two pins out.  The right punch is critical!

Knock out from left to right and install pins right to left.

I use a dead blow hammer made of plastic to them knock of FSB.  Does not marr FSB.

When installing new FSB, you need to make sure you mark where the gas port hole is...

[url=http://www.kanolabs.com/]Kroil[/url] is creepy stuff. It is available factory direct and also from [url=http://www.midwayusa.com/rewriteaproduct/137203]Midway[/url] among other sources.

It is a required "soft tool" for cleaning suppressors.