Removing and reinstalling AR front sight base

turtlehead · November 6, 2017, 08:15 AM

A friend of mine has his mind made up to replace the round hand guard on an M4 with a triangle carbine hand guard. Yes, they make those. I had no idea.

The new hand guard uses a triangle end plate. So the fsb will have to come off and be reinstalled.

I've removed them before but never put one back on. Will it be good and tight as the original? Will I need new pins? Is this a bad idea? If it was up to me, I wouldn't do it...

burrhead · November 6, 2017, 01:24 PM

It's not a problem, the FSB will be plenty tight when re-installed. Reuse the old pins. Just don't baby the pins when driving in or out. I use an 1/8 inch nail set.

444 · November 6, 2017, 01:32 PM

I don't see it as being a bad idea.
If that is what he wants, do it.

Unless you damage the pins taking them out, no you won't need new pins. As you know, the pins are tapered. When you drive them back in they will be as tight as they are now.

turtlehead · November 6, 2017, 01:45 PM

Thanks, guys.

Ibmikey · November 12, 2017, 06:57 AM

Some manufacturers use straight pins, most are taper but enter from either side so be sure to measure ends and take them out correctly. A front sight block really helps with this project as some pins will be stubborn.

Nathan · November 12, 2017, 07:49 AM

I see this as a bad idea.....only because of the level of challenge it is.

You need a solid bench and a solid bench block or wood block clearanced with holes behind the pins.

You need steel starter punches to get it going. Actually I use a larger tapered punch just to break it free, then a starter punch, then a pin punch. .....and a 2 lb hammer.

The pins go only one way. Look it up or measure the heads.

After the pins are removed, you need something to break down the carbon. It will likely be frozen to the barrel.

Then there is the gas tube. It's pin is 5/64". IMO, you will want a roll pin holder, a roll pin punch and a roll pin starter punch. It too will be frozen. It might be better to remove the fsb and tube as an assy to avoid this.

Enjoy. It is one of my least enjoyable AR tasks.

10-96 · November 12, 2017, 09:33 AM

I may be wrong on this, but the feller hadn't ought to have to remove the gas tube from the FSB unless it inadvertently gets mangled while getting the FSB off.

He might need a new peel or crush washer behind the muzzle device so it will index back to where it was before disassembly.

turtlehead · November 12, 2017, 11:50 PM

I was mostly worried about it being tight after reinstalling it. I have the tools and the bench, it's just something I'd rather not do.

stagpanther · November 13, 2017, 02:08 AM

Quote:

Enjoy. It is one of my least enjoyable AR tasks.

Agreed--I've had extreme difficulty getting one off without damaging it--in addition to "carbon freeze" it seems like some outfits put phosphate treatment on after the sight is installed--that sort of creates it's own weld

November 6, 2017, 08:15 AM	#1
turtlehead Senior Member Join Date: October 20, 2015 Location: Phoenix, AZ Posts: 1,203	Removing and reinstalling AR front sight base A friend of mine has his mind made up to replace the round hand guard on an M4 with a triangle carbine hand guard. Yes, they make those. I had no idea. The new hand guard uses a triangle end plate. So the fsb will have to come off and be reinstalled. I've removed them before but never put one back on. Will it be good and tight as the original? Will I need new pins? Is this a bad idea? If it was up to me, I wouldn't do it...

November 6, 2017, 01:24 PM	#2
burrhead Senior Member Join Date: July 6, 1999 Location: Chihuahuan desert, Texas Posts: 1,148	It's not a problem, the FSB will be plenty tight when re-installed. Reuse the old pins. Just don't baby the pins when driving in or out. I use an 1/8 inch nail set. __________________ Join the GOA, SAF and the TSRA I'm offended by people that are easily offended.

November 6, 2017, 01:32 PM	#3
444 Senior Member Join Date: November 20, 2000 Location: Ohio Posts: 3,968	I don't see it as being a bad idea. If that is what he wants, do it. Unless you damage the pins taking them out, no you won't need new pins. As you know, the pins are tapered. When you drive them back in they will be as tight as they are now. __________________ You know the rest. In the books you have read How the British Regulars fired and fled, How the farmers gave them ball for ball, From behind each fence and farmyard wall, Chasing the redcoats down the lane, Then crossing the fields to emerge again Under the trees at the turn of the road, And only pausing to fire and load.

November 12, 2017, 09:33 AM	#7
10-96 Senior Member Join Date: October 19, 2005 Location: Tx Panhandle Territory Posts: 4,159	I may be wrong on this, but the feller hadn't ought to have to remove the gas tube from the FSB unless it inadvertently gets mangled while getting the FSB off. He might need a new peel or crush washer behind the muzzle device so it will index back to where it was before disassembly. __________________ Rednecks... Keeping the woods critter-free since March 2, 1836. (TX Independence Day) I suspect a thing or two... because I've seen a thing or two.

November 6, 2017, 01:45 PM	#4
turtlehead Senior Member Join Date: October 20, 2015 Location: Phoenix, AZ Posts: 1,203	Thanks, guys.

November 12, 2017, 06:57 AM	#5
Ibmikey Senior Member Join Date: June 1, 2013 Location: Now relocated to Texas Posts: 2,943	Some manufacturers use straight pins, most are taper but enter from either side so be sure to measure ends and take them out correctly. A front sight block really helps with this project as some pins will be stubborn.

November 12, 2017, 07:49 AM	#6
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,328	I see this as a bad idea.....only because of the level of challenge it is. You need a solid bench and a solid bench block or wood block clearanced with holes behind the pins. You need steel starter punches to get it going. Actually I use a larger tapered punch just to break it free, then a starter punch, then a pin punch. .....and a 2 lb hammer. The pins go only one way. Look it up or measure the heads. After the pins are removed, you need something to break down the carbon. It will likely be frozen to the barrel. Then there is the gas tube. It's pin is 5/64". IMO, you will want a roll pin holder, a roll pin punch and a roll pin starter punch. It too will be frozen. It might be better to remove the fsb and tube as an assy to avoid this. Enjoy. It is one of my least enjoyable AR tasks.

November 12, 2017, 11:50 PM	#8
turtlehead Senior Member Join Date: October 20, 2015 Location: Phoenix, AZ Posts: 1,203	I was mostly worried about it being tight after reinstalling it. I have the tools and the bench, it's just something I'd rather not do.