[ARCHIVED THREAD] - help with front sight

Posted: 3/2/2011 12:40:46 PM EDT

I bought a A2 front sight to replace one on my ar pistol that had been milled down. The problem is the pins will not line up on my barrel. The ones on my barrel are farther apart than the new front sight. anyone have this problem and is it common? the barrel is a s&w. Thanks for any help.

Posted: 3/2/2011 12:45:20 PM EDT

[#1]

Quoted:
I bought a A2 front sight to replace one on my ar pistol that had been milled down. The problem is the pins will not line up on my barrel. The ones on my barrel are farther apart than the new front sight. anyone have this problem and is it common? the barrel is a s&w. Thanks for any help.

If you are replacing the entire front sight and the pins are the ones through the barrel you have two options.

1. send it off to ADCO (or another company to be pinned...

2. install a clamp style front sight/gas block

Front sight posts are not interchangable...each is drilled specifically for each barrel using a jig...

Mike

Posted: 3/2/2011 12:47:31 PM EDT

[#2]

Thanks Mike. Didnt know that. Thought they were mil spec and would fit the same.

Posted: 3/2/2011 4:15:02 PM EDT

[#3]

I always wondered about this.

If they are drilled with a jig, and IF the jig conforms to some standard, then why aren't the FSBs interchangeable? Notice the big IF.

Posted: 3/2/2011 4:46:47 PM EDT

[#4]

My guess is that tolerance stacking is more evident in places where a tight fit is achieved like FSP or barrel extension / bolt face.

Posted: 3/2/2011 5:24:47 PM EDT

[#5]

But with a jig, you only need to adhere to very few tolerances, namely spacing of the drill holes and diameter of the drill and reamers. These should be easily controlled.

Posted: 3/2/2011 5:45:38 PM EDT

[#6]

Jigs wear like everything else.

[ARCHIVED THREAD] - help with front sight

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[ARCHIVED THREAD] - help with front sight

[ARCHIVED THREAD] - help with front sight