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Posted: 5/10/2015 4:35:01 PM EDT
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OK - First - I searched and searched and never found exactly what I am about to ask:
Has anyone taken a shaved low-pro Front Sight Base and drilled for set screws? I have several barrels that are not set up for taper pins and a pile of old A2 FSBs that I can cut up. Have done several shaved before but never with set screws. Anyone done this? Any reason NOT to do this? Exactly how did you do it? One or two set screws? Have Rocksett. Thanks for the help! FH EDIT: Can you also just cut off the bayonet lug and the sling mount and add set screws so you can use the A2 FSB as a sight? Here I would imagine you would really need to dimple the barrel to make sure it didn't rotate if the sight is hit by something! |
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You could do it.
I have a NM FSB with set screws. They are used to dial in the FSB to top dead center. Normally there are four "flats" machined into the barrel for the setscrews to nest into. If you don't cut the "flats" the set screws bump a curved surface which is not ideal. https://www.ar15.com/archive/topic.html?b=3&f=4&t=493323 |
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Quoted:
You could do it. I have a NM FSB with set screws. They are used to dial in the FSB to top dead center. Normally there are four "flats" machined into the barrel for the setscrews to nest into. If you don't cut the "flats" the set screws bump a curved surface which is not ideal. https://www.ar15.com/archive/topic.html?b=3&f=4&t=493323 Thanks for the archived thread. I thought about that but if you do not have the side flats I think it would not be ideal - the set screws would be hitting at an acute angle on the barrel. I may try to take off the sling and add the set screw under that then drill all the way thru the bayonet lug and tap that. Drill size & tap recommendations? Thanks! FH |
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Quoted:
Thanks for the archived thread. I thought about that but if you do not have the side flats I think it would not be ideal - the set screws would be hitting at an acute angle on the barrel. I may try to take off the sling and add the set screw under that then drill all the way thru the bayonet lug and tap that. Drill size & tap recommendations? Thanks! FH Quoted:
Quoted:
You could do it. I have a NM FSB with set screws. They are used to dial in the FSB to top dead center. Normally there are four "flats" machined into the barrel for the setscrews to nest into. If you don't cut the "flats" the set screws bump a curved surface which is not ideal. https://www.ar15.com/archive/topic.html?b=3&f=4&t=493323 Thanks for the archived thread. I thought about that but if you do not have the side flats I think it would not be ideal - the set screws would be hitting at an acute angle on the barrel. I may try to take off the sling and add the set screw under that then drill all the way thru the bayonet lug and tap that. Drill size & tap recommendations? Thanks! FH Seems like mine were 8-36 but that archived thread talks about 8-32. My FSB came from White Oak Armament...so what ever they use. |
| If you have a drill press with an X Y vise, or access to one, it's easy enough to drill a barrel for taper pins. Once you have the barrel and FSB lined up, start with an 1/8" EM, even a dremmel tool rasp will work, just to get the flats started. Then drill and ream for the taper pins. |
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Quoted:
If you have a drill press with an X Y vise, or access to one, it's easy enough to drill a barrel for taper pins. Once you have the barrel and FSB lined up, start with an 1/8" EM, even a dremmel tool rasp will work, just to get the flats started. Then drill and ream for the taper pins. Have you got part numbers and where you got the drills and reamers from? Any Jigs? Carbide End Mill to cut all the way thru barrel or just till you get a flat for the drill bit? Thanks, FH |
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Taper pin reamer from Brownells. I don't remember what size drill bit, but an 1/8" endmill or rasp will get a flat so you can drill the rest of the way. No jig really needed, but they are out there. The gas block journal is .75" Buy a piece of 3/4" rod to practice on if you are unsure of your abilities.
Just go slow and make sure nothing moves. Measure twice, then measure again. It's a pretty easy job. It's about $65 for such a job, but I've done em for nothing. |
| I put screws through all 4 taper pin holes (used FSB) and one through the hole near the sling and another up through the bayonet lug. I think I used size 10 screws. Once I got it aligned I had a new allen wrench for each screw and put red loktite on it and cranked untill the wrench bent. |
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Quoted:
Taper pin reamer from Brownells. I don't remember what size drill bit, but an 1/8" endmill or rasp will get a flat so you can drill the rest of the way. No jig really needed, but they are out there. The gas block journal is .75" Buy a piece of 3/4" rod to practice on if you are unsure of your abilities. Just go slow and make sure nothing moves. Measure twice, then measure again. It's a pretty easy job. It's about $65 for such a job, but I've done em for nothing. I'm trying to picture this, not why are you cutting a flat? Set screw install? The FSB and barrel are typically drilled at the same time when doing taper pins. |
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Quoted:
I'm trying to picture this, not why are you cutting a flat? Set screw install? The FSB and barrel are typically drilled at the same time when doing taper pins. http://nebula.wsimg.com/obj/Qjc3QzYxNjk1QTNDRTgxQzM1RDE6MWFmMzBmYTEzNTc3ZTcwYjBiOWU0ZGM3Mjc4ZTBhOWU6Ojo6OjA= Quoted:
Quoted:
Taper pin reamer from Brownells. I don't remember what size drill bit, but an 1/8" endmill or rasp will get a flat so you can drill the rest of the way. No jig really needed, but they are out there. The gas block journal is .75" Buy a piece of 3/4" rod to practice on if you are unsure of your abilities. Just go slow and make sure nothing moves. Measure twice, then measure again. It's a pretty easy job. It's about $65 for such a job, but I've done em for nothing. I'm trying to picture this, not why are you cutting a flat? Set screw install? The FSB and barrel are typically drilled at the same time when doing taper pins. http://nebula.wsimg.com/obj/Qjc3QzYxNjk1QTNDRTgxQzM1RDE6MWFmMzBmYTEzNTc3ZTcwYjBiOWU0ZGM3Mjc4ZTBhOWU6Ojo6OjA= He's talking about "old" FSB's. I take that to mean already drilled. Line up on the pre-drilled holes, use an EM to create flats on the virgin barrel so the drill bit doesn't try to walk and ream the FSB before it starts into the barrel. If enough care is taken the results can be as good as a virgin set drilled together. |
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Quoted:
He's talking about "old" FSB's. I take that to mean already drilled. Line up on the pre-drilled holes, use an EM to create flats on the virgin barrel so the drill bit doesn't try to walk and ream the FSB before it starts into the barrel. If enough care is taken the results can be as good as a virgin set drilled together. Quoted:
Quoted:
Quoted:
Taper pin reamer from Brownells. I don't remember what size drill bit, but an 1/8" endmill or rasp will get a flat so you can drill the rest of the way. No jig really needed, but they are out there. The gas block journal is .75" Buy a piece of 3/4" rod to practice on if you are unsure of your abilities. Just go slow and make sure nothing moves. Measure twice, then measure again. It's a pretty easy job. It's about $65 for such a job, but I've done em for nothing. I'm trying to picture this, not why are you cutting a flat? Set screw install? The FSB and barrel are typically drilled at the same time when doing taper pins. http://nebula.wsimg.com/obj/Qjc3QzYxNjk1QTNDRTgxQzM1RDE6MWFmMzBmYTEzNTc3ZTcwYjBiOWU0ZGM3Mjc4ZTBhOWU6Ojo6OjA= He's talking about "old" FSB's. I take that to mean already drilled. Line up on the pre-drilled holes, use an EM to create flats on the virgin barrel so the drill bit doesn't try to walk and ream the FSB before it starts into the barrel. If enough care is taken the results can be as good as a virgin set drilled together. I got ya. As long as your spindle is set in the same plane as the existing hole works fine. The only issue that concerns me on using old FSB's is over reaming and needing to to a 0 pin. |
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