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Installing Bulgy FSB and gas block and jave a couple question?


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After removing the original fsb seems like I remember seeing on someone else's build one pin notch under there. Is that pretty common? Or is it a crap shoot? The reason I'm concerned is that I don't want to install the new one canted, and figured if there is atleast one pin notch for each. I could install one pin to line it up before drilling or reaming. After I remove the original fsb, what size bit/reamer do I need to make the notches? I'm going to be using standard size pins. I'm leaning toward getting a reamer and using my friends drill press. Any help would be really appreciated. Thanks,

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You should be able to do everything with an end mill, in one pass.

If I'm not mistaken (verify the size), they are 2.5-3mm pins for a fsb (mic your pins). I would look for a 2 flute 3mm end mill on amazon, made for center cutting. Its short, stubby and sharp, it won't distort like a longer drill.

I doubt a dimple on fsb will have any notches under it.

 

If your new fsb measures the same from front to back, as the old one, then measure the distance from the front edge of the gas block to to the back of the fsb and install the new fsb at the same spacing.

Or, if your old fsb is not canted/crooked, you can drill out the unused pin holes on it (before removal) so you'll have perfect placement of the new fsb. Assuming the pin hole spacing is the same from old to new fsb. Verify center to center with a pair of calipers.

 

There will be one notch for the gas block because like Captain Hero said, the pin that holds the hand guard on also retains the gas block, which might be what you'd seen before. If you plan on using that notch, you need to measure the gas block overall length (new vs old) to determine if it will line up with the gas tube correctly.

Measure measure measure all parts new and old in multiple places and compare.

Edited by Mullet Man
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My FSB was pinned, as I think all are now.

 

I pressed the Bulgy FSB on so that the new pins would be in front of the old ones. The old ones didn't fit anything I had in the shop, so it was easiest to just not press it on all the way, and do new holes. I could see some of the old notch sticking out from the new base, so I just eye-balled it to make sure I had room for new pins. So I got it on, shot it to verify zero (it's solid on there, didn't move at all during transport, shooting, and transport, but I still painted a stripe going from the base to the barrel so that it would show me if it moved any), and then let the dimples in the FSB guide a 1/8" bit. I then cut some 1/8" drill stock to length, did a crude heat treat, and installed those. It's solid, and took me no time at all. The dimples in the new FSB helped, as all I really had to do was make sure the bit was square to the base. Having a shop press was a MASSIVE help, though.

Edited by Inebriated
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I swear it looks like there are pins in the fsb too. It looks like pins on one side of the fsb and the other side is flush. Did they crimp the dimples and put pins in? The one side that is smooth looks like they may have welded and then ground it off? I scraped some of the paint off the smooth side, and it looks like the outline of the pins under there?

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It's either pinned or dimpled. Not both, and not welded. Mine needed a solid setup to get them out. I ended up using the metal frame of my press, had a buddy hold it steady, and wailed on it with a hammer and a good punch. It'll go, you just have to make sure all the energy is going into the pin. Also, some Liquid Wrench won't hurt. Also, make sure you're going from left to right.

Edited by Inebriated
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Well they came off pretty easy. I drilled a little into the dimples and cut down each side with a cutting wheel. Then I took a chisel and hammer and smacked my cuts, and the broke loose pretty easy. Sorry Risky, unless you want to try welding them back together? I trial fit the new gas block and fsb, and they seek like they will go on without a whole lot of trouble. Do I need to press these on with a press, and if so how? Or can I just put them on the oven or something like that and drive them on gently? Thanks 

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Well I actually only used my press for fine adjustments, mine was able to just be whacked on with a rubber mallet and a buddy holding the rifle. That was nice, because I was able to also whack it to adjust gross windage at the range. So I'd say that you don't actually need the press for that, but I found it to just be easiest for getting it exactly where I wanted for drilling the new pins.

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