problems installing AR-15 Front sight

Power Pill

Power Pill

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Im trying to install a standard front sight onto my AR-15...but i cannot get the set pins to go in at all...there doesn't appear to be a big enough gap between the barrel and the holes for the set pins. I tried hammering them in a couple times, but it just twists the front sight...

This barrel has never had a front sight on it. i purchased the barrel brand new and just put a clamp on gas block on it.

the barrel is .750 and so is the front sight.

Any help guys?

thanks :D
 
The pins need to go through holes drilled in the lower radius of the barrel.

If your barrel doesn't have these holes, there's no way you can install a pinned on FSB. You'll have to use a clamp-on or set-screw type base.

Didn't you notice you couldn't see through the holes you were trying to pound pins into?
 
Stevo said:
Didn't you notice you couldn't see through the holes you were trying to pound pins into?
Click to expand...

yeah

"there doesn't appear to be a big enough gap between the barrel and the holes for the set pins"


Could i know put these holes into the barrel? with say a drill or file them?
 
Power Pill said:
yeah

"there doesn't appear to be a big enough gap between the barrel and the holes for the set pins"


Could i know put these holes into the barrel? with say a drill or file them?
Click to expand...

I read that in your first post. I just couldn't figure out why you'd try and pound the pins through a non-existent gap.

You could try and do it yourself, I suppose. I wouldn't try without a jig, a big drill press, and someone who knows how to do it. YMMV.

Your best bet is to send it to someone who has the skill and tools, or go back to your clamp on.
 
Pinned front sight bases might use (depending on make), tapered pins, straight solid pins, or roll pins.
If I were forced to attempt this job, I would carefully mark where the "half holes" would be on the barrel, and gently file them with needle files, until they were almost cut to full depth. I would then put the front sight base in place, using a bonding agent to make sure it didn't shift, and finish the holes through both the front sight base and the barrel with a taper pin reamer, then install taper pins. Or, clean up the holes with a drill and/or reamer, and install straight pins. The taper pins are superior.
If a pinned front sight base is desired, it would be better to start with an undrilled front sight base, an undrilled barrel, and cut them together.
There are other ways to mount front sight bases.
In Zediker's book on building competition grade ARs, he shows methods of mounting sight bases with set screws - not straight in against the barrel, but engaging the barrel at a tangent, the tip of each setscrew making contact with a milled flat on the barrel. I supect that this would be the best way of installing your front sight base, four setscrews being installed in the pin holes.
 
When the front sight bases are installed onto the barrels at the factory, there are no holes in either part. The holes are drilled and then taper reamed with part of the hole going into the barrel. This of course is all done on a jig with the sight indexed with the barrel extension pin. This is why you cannot swap front sight bases between different barrels. If you get one that lines up and indexes properly, you are very lucky.

For many years all front sight bases had taper pins. Lately there are some with straight pins and some with roll or split pins. There are a lot of variations around.

I have done both fitting undrilled sight bases to barrels with notches from previous sights, and used front sight bases with holes onto undrilled barrels. Both can be done but it does take a while to set it up.

Casey
 
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