"Bubba-smithing" my AR

[Willociraptor]

SHORT PREFACE
I've been shooting this 20" BCM since I bought it in 2016. It's great. I'm a big fan of 20" AR's. Fairly vanilla at first glance, but, as Han Solo once put it, "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
I want to freefloat it. I've toyed with the idea for years, and have learned how to shoot it at distance as-is (not freefloated), but finally decided to do it. But having my sweetheart rifle worked on was a nerve-racking proposition. I don't consider myself a guru, but I know my way around AR's, and I know this rifle better than I know my wife. My wife is the human being I know best, but she's still a human being with nuances and quirks and layers. And to further complicate her, those things change over time. The rifle, on the other hand, is just a machine. It operates based on mechanical certainties. And I believe in my abilities, so I decided to claim this project for myself.
Just wanted to share the story of how I did this little project. Whenever I do my own work, I try to document it as I go so that (a) if I mess something up then I can backtrack my steps and fix the mistake, and (b) I can share lessons learned with other people.
Primary moral of the story is - when working on BCM stuff, be prepared to either take it to a gunsmith or pull out the heavy equipment.
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OKAY NOW FOR THE WRITEUP
Got all my stuff together. Vised up the rifle and literally said a prayer going into it. This is the rifle I trust to defend the lives of my family and my countrymen. Please help me take good care of it and put it back together properly.

Having to deal with the FSB was a known obstacle from the outset. I've never removed one before, but I have the booksmart knowledge of how it's done, plus the needed equipment. Figured it was within reach. So I got to work.
I realized I didn't have any big-fat-faced punches, so I found a tool I don't use much and chopped off the pointy end to be able to use the main shaft as a full-width punch.



The videos I've seen usually recommend a heavy hammer, 2lb or better. Heaviest hammer I have is a 28oz milled-face framing hammer, but the design of the handle made me feel like I could close the gap from 28 to 32oz with sufficient angular velocity. But that meant swinging pretty hard, which of course made me nervous about possibly missing the punch and pulverizing my hand. I pulverized my right hand one time and long story short I'd rather not repeat the process with the left hand. Took some scrap wood and drilled a hole in it to hold the punch, and I was able to hold the punch in place from a distance.

This thing just was not budging. Well, maybe it budged, but tectonic plates "budge," too. I started to get creative.

I screwed in the press 180 degrees at a time and went well beyond the point where I would've expected it to start working, but still nothing. The plastic jig was visibly warped, being pushed closer and closer to ductile failure. And when it snapped, I'd have a makeshift punch fly SOMEWHERE at approximately Mach 12, plus my barrel would fall and possibly get damaged. So I aborted that approach.
So. That wasn't happening. I wondered if there was a way to finish my project without pulling it off. Could I do it backwards?

I had the idea of slipping the FFHG over the barrel and then installing it that way, but in order to do this and still be able to tighten down the barrel nut, I'd have to find a way to slide the FFHG forward about an inch. From the face of the upper, it came up just short of the FSB the way it's supposed to, but the HG cap was an obstruction. If this was gonna work, that cap would have to be dealt with.

Decided to remove the gas tube first. Punched out the rollpin and removed the gas tube. It's almost as if this rifle has had a few rounds through it. Cleaned up pretty well with some CMP, a brush, and a rag.


Okay back to work. After some trimming and some very careful work with the Dremel and some files, the handguard cap was looking alright.

The hole for the gas tube was a little misaligned. I didn't want any lateral pressures on my gas tube, so I drifted it back into alignment with a couple of light taps from a punch. But then I realized - if this piece of metal can move, then I might as well just rotate it and trim it down nice and tight! So I did.

Okay! Making progress!

Barrel nut unscrewed easily, but pulling the barrel out of the upper was a different story. Usually, you can remove a barrel with just moderate pulling force, but this thing was IN THERE. It was starting to become a theme.. almost as if this rifle was well made. Anyways, clamped the barrel into the vise and gently held the upper with my left hand while hitting it with a wooden mallet in the other hand. After several good whacks, it came off. Cleaned off the factory goop with soapy water.
Okay, now time to remove the barrel nut so I can put the new one on.
But…dang! The barrel nut won't come off. On one side is the barrel collar, and on the other side is the FSB.
Sigh.
What to do???
LOL DREMEL TO THE RESCUE

Yay! Barrel nut removed!
Time for the new barrel nut.
But…dang! Couldn't put the new one on, due to the same constraints - barrel collar and FSB.
Ugh. I was gonna have to figure out the FSB removal after all.

Okay. So. Back to square 2-ish.
Called up a good friend of mine. He used to handle this stuff regularly while working at a top-tier gun shop. I filled him in and asked what sort of backup plans he was familiar with. His immediate response was, "Is it a BCM upper? Yeah, that's gonna be a bear." We talked for a little while and he offered to do it himself if I could ship it to him, but I decided to just take it to a gunsmith.
Well, they weren't able to hammer it out, but they offered to machine it off. I was like um no? (I could've easily done that myself.) They offered to check it in and heat it up and whatnot, remove the FSB, and get it back to me. I said no thanks and figured I'd just work it out myself using the "buy a bigger hammer" approach, instead of paying and waiting for them to remove it, then paying and waiting again for them to reinstall it.

So that's what I did.
For less than half of what I would've spent on gunsmithing services, I stopped at Home Depot and bought a 4lb hammer.

I sure am glad I had that punch-holding jig, because I was really letting that thing have it! I had to wail on it pretty hard, but the bigger hammer got the taper pins dislodged. The rest of the operation required smaller punches, and the big hammer quickly wrecked a couple of them. Chopped one of them down to much more stout and less fragile dimensions.


Once the taper pins came all the way out, the rest of the project took like 15 minutes. But getting those blasted taper pins out took me most of the day.
FSB slipped right off, applied anti-seize to the upper receiver threads and the front of the barrel collar, barrel nut went on, gradually torqued the barrel nut into place, installed the handguard, put the "handguard cap" back on, pinned the gas tube back into the FSB, slid the FSB back onto the journal in alignment with the gas tube hole, reinstalled the muzzle device, and got the taper pins most of the rest of the way back in. Had to wail on it a bit more to get them fully seated back into place, but got it done.

The handguard is a little skinny for my liking, but I'll get used to it.
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So those were my misadventures in Bubbasmithing my fighting rifle. Hope it helps somebody!

[ScubaSteve]

Gunsmithing 101. Get a bigger hammer!

[Charles McKinley]

You need to make friends with a boilermaker or a blacksmith or a boilermaker that does blacksmithing.  When all else fails INCREASE HAMMER SIZE!

Glad the project was a success.

[Burnett]

A trick that was shared with me early on in my AR journey is to use a nail set to drive the taper pins out. The face is a bit concaved, which helps avoid slipping. The are pretty brittle and so won't last for very long, but they're cheap. The come in at least three sizes and it too big night wedge firmly into the hole, so be aware of that.

*** It occurs to me thatnot everyone might know what a nail set is. They are small punches used to drive "set" finish nails below the surface of wood.

[HardHolder]

Good job Will!

In the Army we used to say. "If it don't fit don't force it, get a bigger hammer"

[Willociraptor]

Just wanted to offer an update. This whole thing has been a test of my knowledge, equipment, skill, and confidence. But A RIFLEMAN PERSISTS!

So. Awaayyyy we go!

• Did some shooting on Monday 4/18 at a local 25yd indoor range, to assess performance and dial in my zero. It was the first time the rifle was fired since being unbuilt and rebuilt.
• Shot a few groups scoped to verify group precision, then a few groups with irons to reestablish zero, then a few groups with the red dot reinstalled to finalize my zero. Did great!
• Even gathered chronograph data to have a reliable average muzzle velocity value to plug into my ballistic calculator in preparation for the KD on Tuesday 4/19.
• At the KD on Tuesday 4/19, I shot this rifle with the red dot and a vanilla USGI web sling for two of the three AQT's. Shot a 48/50 and a 44/50! Means I can assemble a nice tight rifle. It's just an AR, it requires nowhere near the finesse of blueprinting a bolt action, but still. Nice to undergo a test and pass with flying colors.Super duper affirming experience!

Bubbasmithing project was a yuge success!