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Posted: 7/16/2011 5:41:44 PM EDT
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Hi everyone.
I'm kind of a newbie to ar15/m16 rifle building. Spend most of my time building ak type rifles, so I could use a little help from the experts here. I bought one of the Colt kits, and it looks great. Mine came with a bare barrell without front sight post installed. I was trying to test fit the barrel to the upper and the alignment pin is too big to fit into the slot. Should I open the slot up, or try and trim the pin? Also the front sight will not fit. It appears that the barrel was not lathed down far enough. I tried several times but the sight just isn't going to fit. I thought that maybe I could put some sandpaper on a cotter pin and use a dremil to open up the sight base so it will fit. Does that sound like a good option? Also, can you drill out the barrel for pins and press fit the pins in like an Ak? Last question, there is a blemish on the upper than is fairly large. What are people using to refinish their guns? Gunkote? Thanks for any assistance. |
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The front sight base is centered up and aligned with the barrel index pin. It takes a good jig set-up to get the fsb positioned and drilled just right. I would send it off to have someone like ADCO do the work, and get it right the first time.
The barrel index pin should be a tight/snug fit, but if you open it up, it can cant the front sight one way or the other. Tapping the barrel in sometimes works, just don't bash it too hard. Guncoat works well for refinishing the upper and lower receivers to get the colors to match and make it look new. HTH |
| The kit upper is Colt manufacture and should be in spec. By how much is the pin on the barrel extension too large to fit into the slot of the upper? You may want to try to get a barrel exchange from your vendor. Does the FSB have any burrs that would result in it not fitting the barrel? Can you measure the OD of the part of the barrel that is interfering with the fit of the FSB? Where on the barrel does the FSB not fit? The FSB was originally mounted with taper pins. The barrel will need to be slotted for the pins and then a taper reamer used for the final hole size. As noted before, you may want to consider sending the barrel and FSB to Adco Firearms for this installation. See the part of the website for Adco that has to do with shop services. You can send the upper to US Anodizing for a strip and reanodizing. |
Just an update. I managed to get the barrel mounted to the upper. The pin was .007 larger than the opening, but apparently only on the end. Tapping with a plastic hammer gently let it seat. The front sight base needed some polishing, then again some gentle tapping with a plastic hammer got it seated. I thought hammers were only useful on my ak builds
I believe I'll send it off to get the FSB properly pinned and refinished. Thanks for all the help! |
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