6920 FSB removal ?

The FSB is held in by taper pins and will be TIGHT.

The best procedure is to douse them with a good penetrating oil and let them sit over night. If you don't have an FSB bench block, use a block of hardwood on a solid surface to support the FSB, and while someone helps you by holding the upper, drive them out from left to right using a 5/16 starter punch and heavy hammer, at least 12oz. Once they are flush, use a pin punch to push them through. DO NOT use a pin punch to start them moving, you WILL bend the punch.

Do not "tap" on the pins, hold the punch firmly against the pin and strike the punch squarely. It may require several blows to break them loose.

If you damage the pins, replacements are about $5 from various vendors. You can also find various size taper pins a better stocked hardware stores.



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To add to the above, Colt didn't flare the tapered pins, so unless someone has deformed them they should not be flared.
The pins are installed from the right side and driven out from the left side, as you'd sight down the barrel.
This is Colt factory standard, but make sure someone hasn't changed the pins around.

To prevent deforming the pins and causing them to lock in place, get the assembly in a well braced no bounce-no move setup.
If you strike the punch and anything moves, the force is dissipated and the pins can deform instead of moving.
If necessary get a buddy to help hold it steady.
You can use hard wood blocks or a special bench block from Brownell's, but the trick is to not have any force applied to the sight tower that might cause it to rotate on the barrel. In other words you don't want to rest the upper portion of the tower on a block, you want the pin area on the block with clearance for the pins to move out.

It must be on a firm surface that won't give. A concrete floor works well. Wrap everything in towels or whatever to prevent any chance of scratching and pay attention to what's going on with the other end of the upper while you're working on the sight tower.

Use a starter pin punch as above, which is nothing more than a punch that's been cut off to about a 1/2 inch working length. The shorter length prevents the punch from flexing or bending, which again, dissipates the force.
Another good starter tool is a nail set. This can't flex or bend.

Use a proper hammer, best if you can use a smaller dead blow hammer that will direct all the force to the pin with no bounce.

Once the pins are moving out switch to a standard punch to fully remove them.
If the pins look deformed at all, buy a new set.

Also as above, apply a good penetrating fluid to the pins and the sight tower and let soak overnight. Kroil is the best and can be bought at many gun stores and from Brownell's.

To remove the actual sight tower, use a really hard wood block to gently tap the tower forward. Move the block from the top side to the bottom side of the tower each tap to prevent deforming the tower and causing it to lock in place.
Make sure you have plenty of Kroil or other penetrating fluid around the front and rear barrel ring area of the tower to lubricate it.

When reassembling the tower to the barrel, wipe all the penetrating fluid off the tower and barrel and use a lubricant like CLP Breakfree.
Go slow and easy and keep the tower aligned so it isn't rotated off top-dead-center. DO NOT count on the pins to re-align an off-center tower. Instead of aligning the tower, the pin holes may just be enlarged.

I have this front sight base cradle by Schuster Mfg.

I bought this cradle from AdcoFirearms.com (OH) it is made from high density plastic material so it is non-marring, it supports the front sight base for installing and removing taper pins plus also sling swivel rivet installation/ removal tool (about $34), there are similar tools like it from Brownells, MidwayUSA, etc.

This I use on my concrete garage floor because when I use it on my shop table it bounces too much, also I would recommend using several layers of masking tape or duct tape facing the hammer to prevent any scratches or marks on your front sight finish.

I do the same as the other members said, at first I was using a regular size steel hammer but it wasn't getting me anywhere so I used a medium size sledge hammer, you also have to hit it like you mean it with force, it's a PITA to remove and install front sight taper pins.

Since 2005 I had been building my own AR mostly Colt, a LMT and a RRA, all turned out fine but if anything happens to my builds I would know how to fix it.