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Posted: 12/26/2005 7:48:03 AM EDT
| Just discovered that the FSB on my Fulton Armory Classic M4 Carbine is windage adjustable. Can someone enlighten me on this? Is this a good thing? Why is it necessary? Thanks... |
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Windage adjustable? I've never seen that on a AR front sight, AR front sights should only be elevation adjustable. Is it a good thing? Well it would allow your BUIS to be centered so you can zero using only the front sight. I don't think it's needed, nor desireable (you now have a non standard part); but if you like then don't wory about it - go and enjoy your carbine! |
Do you want to go through a bayonet course with one? DMRs are a 'special purpose' weapon, not a general issue. They are also intended to be used with optics If you can loosen the screw to adjust the zero of the front sight, then dollars to donuts you can wack it hard enough to move it. Maybe it's just the engineer in me, but a friction fit doesn't seem to have the strength to prevent rotation that a double pin setup has. |
+1 Windage adjustable front sight bases are fine in range queens, but I would never want one in a rifle that will or could see more heavy-duty use. Just move the windage knob to zero the weapon and put a big, painted witness mark on the knob. |
The ones I am familiar with they are not friction fit... the barrel has four plunge cut channels (two on each side) that the screws go into and face up with steel, y'ould have to whack it pretty hard to move it (something would have to break). |
Generally, the screws are adjusted once, then loctited in place. you can search in the "barrels, uppers, etc.." forum for an old discussion about set screw FSBs, where an GWOT/OIF veteran discussed the durability of his set screw FSB, which was on an M4 upper. I think an approximate quote was "Sometimes you need leverage to get those cot frames put together." also, maybe it's the engineer in me, but you seem to not completely understand how the setup is put together. There are milled flats on the barrel that opposing set screws tightened against. |
They system I've seen doesn't use flats. It just clamps - the screw takes the place of the taper pins (except they don't go through the barrel). Nothing but friction to prevent rotation. |
I've never seen that setup, that sounds like BS. This is how the DMR is setup, as well as CLE, WOA/WOP, AMU rifles, USMC Rifle Team, All Guard Team, etc: www.gswagner.com/arsight/arsightmods2.html |
Found in the civilian world (the people Fulton sells to): Similar unit is sold by Armalite Armalite Catalog p22 |
That is very simular to the setup we use... it is really quite strong. |
That looks like a stronger setup than the clamp on. I haven't been able to get on Fulton's site to see what they use (just not working for me today). |
The adjustments being made are usually in the 1 MOA range or less. More than that, then re indexing the barrel would be required. It's likely that you would see better gas performance; usually a set screw is placed on the bottom of the FSB (where the swivel is), diametrically opposite to the gas port. When the screw is tightened, the force causes a better seal between the barrel and the FSB. |
Since most of us have neither the tools nor the inclination to mess with barrel alignment when zeroing our rifles, an adjustable FSB makes a lot more practical sense. The FSB movement that it takes to bring a group to center is minimal, and has no adverse effect on gas flow. One can theorize all one wants, but the proof is in the thousands of properly functioning rifles out there with a FSB slightly canted to no wind zero, including mine. |
Yes, it takes a small hex key and five seconds. 
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All the Armalite flat top rifles have that clamp-on railed gas block. I've never heard of one coming loose. Do you guys really beat on your canted FSB? Are you trying to turn the barrel in the barrel extension? I think the proper way to do it is to remove the barrel and file slightly the slot in the upper where the barrel ext pin fits. |
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