Front Sight Post

AR/M4 AR Technical Discussion
1

I bought a barrel that was heavily painted by the previous owner. It’s a Saber Defense Gov’t 16" M4 style with an “F” marked front sight base. I’m about to send it off to be refinished so I wanted to remove the front sight post, spring and detent. In the process I mangled the sight up pretty good because it was sealed by all the paint.

I’m looking around for a new sight post, detent and spring and i have two questions:

  1. What height should the sight post be for an F-marked base?

  2. Where should I look for one that doesn’t have shipping rates equivalent to the cost of the parts?

Thanks.

2

FSBs are drilled and pinned to the individual barrels. In other words, the FSB that was on your barrel was the only one that would line up with the pin holes in the barrel. The odds are probably very slim that you would be able to find a FSB that would pin up to your barrel without damage to either part. Sabre Defense huh? How much are you about to pay to have it refinished? You would probably be better off buying a new barrel from a reputable manufacturer and calling it a day.

3

Nevermind my response, I was thinking that you were talking about the FSB, not the post.

4

yeah, I’m talking about the sight post, not the sight base.

I’m getting it refinished through Adco.

5

Here are the two heights for front posts.

Got those from a google search, not my pics.

6

http://www.brownells.com/.aspx/cid=0/k=AR15+front+sight+post/t=P/ksubmit=y/Products/All/search=AR15_front_sight_post

You might try brownell’s. Looks like they have 2 or 3 regular square posts and a few other types. The factory Colt one would be a safe bet for your F marked base.

7

Thanks. Ok, review time, I know the difference between the A2 FSB and the Carbine f-marked FSB, but is there an actual difference in the front sight post. I have understood the taller Bushmaster post to be used as an easy fix to compensate for the lack of f-marked bases.

So in other words, is the .270 post the standard post for the A2 set-up and the carbine set-up? Or is there a difference in actual post height respective to the model AR-15?

8

This is how I understand it. The F-marked FSB are made for flat top carbines but some companies were putting regular FSB’s on flat tops and the irons couldn’t be zeroed without excessive front post elevation so the longer front sight post was invented to give the extra .040" to account for the difference between F and non-F marked FSBs

9

Hello,

Colt Offers a Total of 4 Different Front Sight Post.

SP64665 Short Tapered Post for carbines.

SP64507 Short Square, NON-Tapered Post for Rifles.

SP61706 Round Post for A1 Rifles.

SP62447 Tall Straight Post for 9mm SMGs.

Specialized Armament has all the parts you need. http://www.specializedarmament.com/catalog/Colt_AR_15_Parts-4-0.html

10

Let’s not forget their cheap-commercial “just as good as” carry handles either. https://www.m4carbine.net/showpost.php?p=197917&postcount=9

11

You need the standard height post (.270) and whatever width you prefer, .062 is standard I believe.

12

Ok thanks.

13

Also, just a random 2 cents. If you plan on using the iron sights for a little more than just back ups, consider getting a thinner FSP. they are thinner in diameter and allow you to see more of the target at farther distances. Makes a huge difference if you shoot out to 300 with iron sights.