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1/25/2018 7:38:29 AM
Posted: 3/9/2006 4:07:01 AM EST
Hello anyone that looks at this post. This is my first post on AR15.com and I have been browsing this sight for a few months now. I would like to say that the people here are very helpful, and from what I have seen so far, very decent and respectable. So I am glad to now be a small part of it all. Now for my question.

I have a 20" bushy flat top with a fixed front sight post. I have no clue why they thought that it was a good idea, but now I am stuck with the fact that I have to use a riser for everything. I was wondering if there was a way for me to change out the front sight/block to either just a picatiny gas block, or a flipdown sight/gas block combo. Now I am a beginner so if anyone thinks that this is over my head, is there anyone that provides this type of service? I am located in western viginia. I would like to do this swap so that I don't have to use the riser any more. Personally I think it defeats the purpose of owning a flat top. What do you guys think? Anyways, thanks for any help that I get and I hope you guys stayed awake during all of this.
Link Posted: 3/10/2006 8:52:54 AM EST
No one has an opinion or experience with this?
Link Posted: 3/10/2006 8:59:21 AM EST
Link Posted: 3/10/2006 9:09:36 AM EST

Originally Posted By BookHound:
First, welcome!

Second, I think the reason your post hasn't gotten any hits yet is because it is a little vague. I think what you are wanting to do is replace the FSB (Front Sight Base), which is attached to the barrel using taper pins, with a gas block or flip-up sight base because you believe the FSB will block your view threw the scope. Is that correct?

If that is the issue, you have no issue. Any magnified scope of 3x or higher will "see through" the FSB. It will not block your view.

Does this help?


Yep, 3x or greater and you won't see the FSB. But the switch out is really easy. I just switched out the handguard cap on my carbine yesterday and removed the FSB for the first time. Whole process took me maybe 20 minutes. Just unscrew the flash hider, knock out the two roll pins holding the FSB to the barrel and the one holding the gas tube, slick up the barrel with some lube, and slide the FSB right off. Then all you'd have to do is slide the new one on, hammer the pins back in place and screw the FH back on. The only tools you really need are an adjustable wrench, a couple of punches and a hammer. Couldn't be any easier.

Welcome to the board and good luck.
Link Posted: 3/10/2006 9:17:23 AM EST
Link Posted: 3/10/2006 9:24:32 AM EST
well my problem is I am using a non powered red dot. And when I finally got it sighted in, the dot is sitting about half way down the front sight. I do see 2 pins on the bottom of the block that look like they can be punched out. Just wondering if it is easy to do, or even worth it really.
Link Posted: 3/10/2006 9:33:39 AM EST
Link Posted: 3/10/2006 9:36:24 AM EST
Link Posted: 3/10/2006 9:37:06 AM EST
Wish I had the kind of money to by an aimpoint or EOtech. I have a Tasco 42mm sitting on top of a 1" riser at the moment. If I knew who would host pics, I would post it up.
Link Posted: 3/10/2006 9:37:45 AM EST
Although one day I will have one of those. lol
Link Posted: 3/10/2006 10:40:45 AM EST
Well, there is always the hacksaw method.

Cut the uprights off of the sight, and take a file and smooth/round the remainder.
A little flat black paint and you're good to go.
I have a flat top upper I did this to 2000 rounds ago. Looks factory.
Link Posted: 3/10/2006 4:17:11 PM EST
Link Posted: 3/11/2006 7:04:23 AM EST

Originally Posted By BookHound:
METT-T, you swapped the handguard cap but NOT the FSB, right?

There is no spec for the position of the taper pins. In other words, there is no guaranty the drilled holes in one are in the same place as the hole in another. To install a new, pinned FSB you will need to drill holes into the new FSB. That is IF you are replacing the FSB (like maybe a damaged one) for another standard FSB.

Now, some after-market FSB fixtures, like the PRI flip-up sights and the Armalite FSB, use set screws into the barrel or screws that don't touch the barrel, but clamp the FSB onto the barrel. Make sense?

I just don't want TheAlmightyBob to think all FSB assemblies using taper pins are interchangeable, because they are not.

oops, I stand corrected. I thought they were standard. Still a learning process for me too.
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