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Does the barrel have to be set up in a certain way.in order to use an A2 Type front sight.
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I could be wrong since none of my rifles have the a2 front sight but here goes.
The a2 front sight also has the gas block built into it and is pinned to the barrel by way of 2 holes drilled across the bottom and then the pins are drove in and holds it in throw friction.
I belive there use to be a a2 front sight made that used clamps like most gas blocks now do. JP use to make a a2 front sight that also offered adjustable gas but can't remember how it installed on the barrel.
You could always install a railed gas block and put a flip up front sight on it or install a handguard that lover's the gas block and install a flip up front sight on the end of the handguard.
Hope this helps sir. -
A-2 fixed front sights usually are made for .750” barrel diameters. I have an A-2 on a 22 rimfire CMMG barrel. Instead of taper pins the holes are threaded for four allen screws. I used Red Loctite and it has held for over ten years.
I used a CMMG A-2 clamp on sight which they no longer list but DEZ Tactical does.
Last edited by VASCAR2; 01-16-2019, 02:51 PM.Comment
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The Mil-Spec Front Sight Base attachment method involves a fixture that places the FSB correctly over the gas port, then 2 holes are drilled through the FSB and the barrel and tapered, followed by taper pins being pounded into them to secure it in place.
You can buy a fixture to hold everything in place and use an end mill or drill press to do the drilling.
Fixtures cost more than a new barrel.
Then there are alternative methods:
* Straight pin
* Set screw (with and without dimples or flats on the barrel)
* Clamp on
There are many different ways people have skinned this cat, but the pinned methods are the most secure. The biggest thing I look for with an FSB is that it is TDC, not canted. Canted FSBs are no bueno.NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
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Kevin,
You are going to find that pining the old triangle sight onto a barrel that has not been taper-drilled is more trouble than it is worth. Frankly, you're going to handicap yourself with parts and techniques designed for mass production and average outcomes.
The advice given above by the guys hopefully gives you a sense of what you are up against. I will add to 52's post that when you drill the two holes into the edge of the barrel that the drill-bit needs to be tapered to be authentic, not straight. It requires careful alignment to ensure the sight picture is exactly vertical to the bore axis and if you make a mistake you've stuffed the barrel, at least for pins. You can salvage it by using a clamping or set screw sight base. There was talk when pins were being replaced by set screws and then clamping gas blocks that pins were the most reliable system, especially for the critical reliability required by war fighters. With the advent of clamping and trial and error with glue on the screws that talk has disappeared.
A5 mentions a pickatinny type fixed sight which will be more stable than a flip-up for keeping zero. Daniel Defense makes one that I've used to clamp onto the top of an Adams Arms sight base. The AA piston block has a Pickatinny section on top. Or you can use the same fixed sight on the front of a long-enough rail as long as the rail is stiff enough not to be pulled around too much when you hold it.
To be honest, although you still see companies like Bushmaster still pinning their triangle front sights/gas blocks they are a blast from the past. There are simpler ways available now to achieve what you want. Unless you are building an authentic, nostalgic A2 replica I would forget pinning and mount your fixed front sight by clamping or set-screw.
What are you trying to build?Comment
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The dimples are usually for the gas block.Comment
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Yes, dimples help an old-style front sight/gas block to be vertical to the bore axis. They also align the gas ports of the barrel and the gas block. In your case they will be doing both. Dimples, or a flat surface machined into the barrel (like Lilja barrels) will help keep a triangle front sight from getting knocked about if you are not going to pin it. Keeping that front sight exactly vertical to the bore axis is absolutely critical to precision.
You can buy A2 triangle foresights which have not been drilled from Brownells for about $30-$40. Then populate it with the sight post parts and drill in from the side or bottom to fix it to a barrel. If the barrel has dimples or a flat then you may as well drill in from the bottom and use set screws. Pinning however will not only be more authentic but will be rock solid. You just have to do it perfectly and you get one shot at it.
This is a pretty good deal on right now at Brownells...an old style triangle sight on an 16" AR for $400. Saves you drilling into the sight or paying a gunsmith to do it. Don't know about the barrel quality as I've never had any experie4nce with Anderson.
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I have a WOA barrel that has "windage" flats machined into it for a National Match front A2 sight. The sight is drilled and tapped as you described as well as a locating set screw opposite the gas port.Originally posted by Klem View PostYes, dimples help an old-style front sight/gas block to be vertical to the bore axis. They also align the gas ports of the barrel and the gas block. In your case they will be doing both. Dimples, or a flat surface machined into the barrel (like Lilja barrels) will help keep a triangle front sight from getting knocked about if you are not going to pin it. Keeping that front sight exactly vertical to the bore axis is absolutely critical to precision.
You can buy A2 triangle foresights which have not been drilled from Brownells for about $30-$40. Then populate it with the sight post parts and drill in from the side or bottom to fix it to a barrel. If the barrel has dimples or a flat then you may as well drill in from the bottom and use set screws. Pinning however will not only be more authentic but will be rock solid. You just have to do it perfectly and you get one shot at it.
This is a pretty good deal on right now at Brownells...an old style triangle sight on an 16" AR for $400. Saves you drilling into the sight or paying a gunsmith to do it. Don't know about the barrel quality as I've never had any experie4nce with Anderson.
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