Pinning FSB to stripped BCM Barrel


August 1, 2012, 12:20 AM
I ordered a stripped midlength 16" barrel from BCM and want to permanently mount an A1 style front sight on it. I'm pretty new to building AR's and have been advised to have ADCO pin it for me. I have tried contacting ADCO several times with questions about the process but they are not too helpful with questions.

Iím going to be putting a DD Lite rail on this build which will require the FSB to be removed before installing the barrel and handguard. So what do I do?

I'm not too familiar with what ADCO actually does to install the FSB. Will they simply be making cuts for the correct position of the pins? Should I ask them to make the cuts and leave the sight off, so I can install it when I have the barrel/handguard on? Or can I remove the pins pretty simply myself? Should I get Tapered pins?


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August 1, 2012, 01:10 AM
You will need to send them your front sight. They will mill/drill the holes in the barrel for the taper pins. The pins are pretty easy to remove, although I'm sure that they will remove the sight from the barrel after pinning it, if you ask.

August 1, 2012, 01:23 AM
Thank You!

August 1, 2012, 11:43 AM
Are you against a screw-on FSB?

There's a lot of options. You can do it yourself; and it leaves the potential open for future (as yet unforeseen) upgrades.

August 1, 2012, 04:48 PM
Kiwi, there are other options that you could go with. One would be to use some sort of clamp on low profile gas block and just get a rail that extends beyond the gas block. There are add on front sights designed to go on top of an extended rail.

It's just something to think about, since you're getting the rail anyway. Once you have that barrel cut for the front sight base, it's going to be permanently married to that sight base. When you remove the sight base, the holes will still be there and will not likely line up for use with any other sight base or pinned gas block.

Like I said, since you're getting a rail anyway, you'd just have to get one that's a little longer and add the front sight. I'd just recommend using a clamp on gas block, rather than a set screw type.

Shawn Dodson
August 1, 2012, 06:46 PM
I installed an A.R.M.S.#41 B-L Silhouette clamp-on, folding front sight on my 20" 6.8" barrel.


August 1, 2012, 11:32 PM
Man, I completely forgot about those. That clamp on flip is the way to go, if you want a more conventional front sight.

August 2, 2012, 12:54 AM
I like that A.R.M.S sight, seems more versatile. But I am really looking for the most durable set up I can find. There's no moving parts in an old A1!

August 2, 2012, 02:03 AM
Kiwi, I'd argue that the rig that Shawn posted is more durable in the sense that when it's out of the way, it is less likely to suffer an impact. I also don't know that the model shown locks into place or if it's held in the ready position by spring tension. If it is the latter, it's probably a lot less likely to suffer damage.

I also wouldn't worry about the clamping power of the block. If I'm not mistaken, Adam's Arms tested their gas block, which clamps on the same way, by putting a wrench on the gas block and measuring the amount of torque that it took to twist the gas block. The upper receiver gave way before the gas block slipped.

Still, if you just have to have the pinned FSB. Adco are the people to do it.

August 2, 2012, 09:41 AM
I like pinned FSBs, while a clamp on shouldn't move if properly installed, a pinned FSB won't.

ADCO or any good smith, will have a jig to install an fsb so that it aligns with the barrel index pin. There shouldn't be any cutting involved when installing a FSB, just drilling holes.

If you have the barrel, rails and upper, I would send the whole thing ADCO and have them assemble it.

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