View Full Version : Can an A2 FSB with 4 set screws be mounted straight?
Yes, I know I posted this question on the other websight.....but all I got was one genius reply telling me to send my upper to ADCO. :confused: If this can't be done properly at home, then I want somebody to factually tell me so. If you have war-stories about it, then I'd love to hear them. Surely somebody has attempted to mount the 4 screw style FSB at home?
OK.......
I have an A2 style Front Sight Base that uses 4 set screws (not taper pins). I'm starting out with a new clean barrel.
Is it just a matter of mounting the FSB as straight as my eyes tell me.......and putting some blue loc-tite on each of the screws...... and that's it, I'm done? Or is it deceiving to the eye, and it can end up being slightly canted and off target. (??)
Will the blue loc-tite on the 4 screws hold it firm enough......or do I then need to dremel small flats over the little indents that the screws mark in the barrel?
Your experienced input please.
Here is one way to get it straight, mark a vertical line on the wall, put your upper on a vise, eye ball that vertical line thru the bore and make sure it is centered. Aline your A2 FSB with that vertical line.
There is NO way you can "perfectly" align that FSB but at least you can align it near perfect or acurate enough to hit your target.
If you can buy this barrel with a FSB already installed, I would abandon this project with the set screws.
In my experience, I just aligned it with the forehand rails and eye ball it to make sure that is in its near center.
Perfectly aligned or not, no one can shoot your target perfectly with any gun even in a target rest, recoil eh...
If you can buy this barrel with a FSB already installed, I would abandon this project with the set screws.
Some barrels with pre-installed FSB's have their FSB's canted.
Flats are cut into the barrel for the set screws to engage.
I have never heard of anyone doing what you want to with a set screw front sight and I don't think it will work without the flats.
The idea is for competitive shooters to be able to zero the windage with the front sight. Unless you need that it's a poor choice and it's unacceptable on a fighting rifle.
You should send the barrel to someone who can properly taper pin it.
Yes, I know I posted this question on the other websight.....but all I got was one genius reply telling me to send my upper to ADCO. :confused: If this can't be done properly at home, then I want somebody to factually tell me so. If you have war-stories about it, then I'd love to hear them. Surely somebody has attempted to mount the 4 screw style FSB at home?
OK.......
I have an A2 style Front Sight Base that uses 4 set screws (not taper pins). I'm starting out with a new clean barrel.
Is it just a matter of mounting the FSB as straight as my eyes tell me.......and putting some blue loc-tite on each of the screws...... and that's it, I'm done? Or is it deceiving to the eye, and it can end up being slightly canted and off target. (??)
Will the blue loc-tite on the 4 screws hold it firm enough......or do I then need to dremel small flats over the little indents that the screws mark in the barrel?
Your experienced input please.
it can certainly be done.. i've done a number of them. but the first question is: why do you want a set-screwed FSB? they're really only useful for a very small selection of applications.. DMRs and similar, service shooting, etc- you don't want to use a set-screw on an M4 that's gonna get beat around. if this is a carbine and for home-defense/truck gun/CQB/all purpose/etc, you not only have no purpose for a screwed FSB, but might suffer from it. the biggest risk is having the FSB get canted- and, unfortunately, if it does, it'll probably render the weapon single-shot, as it probably won't stop canting till it's off the gas port. murphy's law.
Here is one way to get it straight, mark a vertical line on the wall, put your upper on a vise, eye ball that vertical line thru the bore and make sure it is centered. Aline your A2 FSB with that vertical line.
There is NO way you can "perfectly" align that FSB but at least you can align it near perfect or acurate enough to hit your target.
scottryan... what you posted is exactly what I opened my thread asking folks not to post. It offers no technical opinion or first-hand experience to explain why you would not attempt it. For all I know, you've never tried it yourself, but your friend with a mallet in one hand and a Coors in the other told you "It don't go on no good". (??)
tonnete and Todd....
Thank you. These are very usefull replies I can mull over!
Tonnete...that is a very helpful installation tip should I decide to proceed. I'm glad you provided it. As well, I appreciate your reasoning that it may not be any less straight then what a smith might provide. It sounds to me like my attempt to install it may have merits..... if I'm very fussy and carefull about it.
Todd, this is the variety of FSB that Fulton uses on most or ALL of their rifles. Would you see harm in me doing small and carefull indents with my dremel? It would give the set screws something firm to lock into. I suppose if the job does not come out satifactorily, the damage caused then should be superficial, and a real pinned FSB would cover over it, right?
Not trying to argue with you as much as I'm trying to pick your brains and see if you could find any redeeming reasons for me to do it on my own.
Thank you gentlemen. I'll continue to read over any other input you or others here might have to provide.
EDIT:
Thank you too BKB.....I was posting while you were.
Hmmm....I'm not planning on using it for combat, but it is a combat weapon, and if S. ever did hit the fan.....it would be nice to know it's not a potential problem. I wonder what Fulton is doing to mount these style FSB's so secure that they are not a concern.
Here is one way to get it straight, mark a vertical line on the wall, put your upper on a vise, eye ball that vertical line thru the bore and make sure it is centered. Aline your A2 FSB with that vertical line.
Works for indexing a barrel, should work for indexing a FSB as well. :)
http://www.weaponevolution.com/forum/showthread.php?t=1613
Thank you too quib.
Guys, all along I mistakenly thought that this 4 screw FSB was designed to be a quick and clean way to install a FSB without the more involved manner of drilling and using pins.
I don't understand the concept of this 4 screw FSB being geared toward competiton shooting or "fine adjustments". Because if lateral windage movements on the target are necessary, wouldn't a shooter just revert to his back sight windage adjustments for all the right or left click that he needs?
In other words, why mess with moving and readjusting the the FSB, when the rear sight is designed to do thatl?
Thank you too quib.
Guys, all along I mistakenly thought that this 4 screw FSB was designed to be a quick and clean way to install a FSB without the more involved manner of drilling and using pins.
I don't understand the concept of this 4 screw FSB being geared toward competiton shooting or "fine adjustments". Because if lateral windage movements on the target are necessary, wouldn't a shooter just revert to his back sight windage adjustments for all the right or left click that he needs?
In other words, why mess with moving and readjusting the the FSB, when the rear sight is designed to do thatl?
I don’t believe the intent of the set-screw FSB was to make adjustments during use.
I believe the intent was to make any fine adjustments that may be necessary at the time of assembly / installation, so that larger rear sight windage adjustments during zeroing would not be necessary.
____________________________________________________________________________________________________________________________________
ETA: A windage adjustable front sight base is standard on the White Oak Precision service rifle upper. The front sight base is forged and machined to our specifications. Opposing set screws are installed in the front of the base to allow for windage adjustment. A single set screw comes up through the bottom of the rear of the base to lock it in place and form a tight seal at the gas port. A 0.052" front sight post is standard, but we can make other sizes upon request. The top and sides of the post are tapered to provide a sharp sight picture. A set screw is installed under the sight post to lock it into place. We adjust the front sight base for windage to center the rear sight during test firing on all of our service rifle uppers.
Source: http://www.whiteoakprecision.com/uppers-service.htm
Here is a pic I found of the flats.
http://www.superiorbarrels.com/images/SDM-Match/windage%20flats.jpg
I would not cut them with a dremel but it's your barrel.
scottryan... what you posted is exactly what I opened my thread asking folks not to post. It offers no technical opinion or first-hand experience to explain why you would not attempt it. For all I know, you've never tried it yourself, but your friend with a mallet in one hand and a Coors in the other told you "It don't go on no good". (??)
We can't give you suggestions until you tell us what type of gun you are building. Are you building a competition gun where this might be necessary or building a fighting rifle? We are now 13 posts deep and this should have been posted in the OP.
Why type of parts do you have? Is this some type of stainless competition barrel or a regular GI style barrel?
Everything you have been told thus far is common general information.
Here is a pic I found of the flats.
http://www.superiorbarrels.com/images/SDM-Match/windage%20flats.jpg
I would not cut them with a dremel but it's your barrel.
QUIB.....
That makes sense what you are saying that it is more for a secondary adjustment if it was needed.
Todd...
Thanks for that photo. No, you're right that the Dremel will certainly not provide the flats and a solid job like that!
Until very recently, it was next to impossible during the last year to get anybody to answer their phone or emails about the work I wanted done. So the next best thing was for me to just buy the 18" Fulton barrel and the 4 screw FSB, which I now have sitting in front of me.
I probably should not think as the DPMS 308 rifle as a serious SHTF battle rifle anyway, and should better rely on my Colt 6920 with its Eotech & BUIS, and its 68gr loads for that. So perhaps in that respect, I'll be OK as long as I'm not thinking of the possibility that I might actually some day be busting down doors with my 308 DPMS and slamming the FSB into hard surfaces.
With the good info I have here thanks to you guys, I now have a clue how this works and what to expect. I'll dremel small marks into the barel to give the 4 set screws and blue-loctite as good a grip as possible. I don't think that these hidden dremel markings will cause any ruin to the Fultron barrel in the event that I ever need to have a REAL FSB installed. In the future, the marks made now would be hidden under a gas block or a new pinnedFSB. So I feel like I don't have anything to lose by installing this FSB, unless I'm overlooking something.
Thanks again. I'm delighted with the knowledge of wealth and the time that you guys took to help me. :) At that other place, which supposedly has more subscribers, this question sat all week with practically no input at all except "Send it to ADCO" which is a lazy answer that teaches me nothing. I guess this place has more aficianados, and the other place has more kids. (??) :D
Center your rear sight. Go shoot. Make windage adjustments by moving the front sight post. When you get it lined up, torque it down and enjoy a frosty beverage.
I was going to buy one of those but instead bought a Armalite clamp on fsb.http://www.armalite.com/ItemForm.aspx?item=EU0240MPKIT&Category=07033031-2a2e-439c-a701-edf0d7327c93 I didn't want to gouge my barrel up in case I wanted to later switch to a low profile gas block. It was easy to adjust windage by moving the fsb around.
I was going to buy one of those but instead bought a Armalite clamp on fsb.http://www.armalite.com/ItemForm.aspx?item=EU0240MPKIT&Category=07033031-2a2e-439c-a701-edf0d7327c93 I didn't want to gouge my barrel up in case I wanted to later switch to a low profile gas block. It was easy to adjust windage by moving the fsb around.
1) You do realize that the FSB you have (if it's like the photo in the link) is a non-bayo lug variety. At first my supplier tried to pawn off one of those on me, and I sent it right back. Though I will never attach a bayonette to my FSB, a neutered and politically correct FSB is something that I will spot right away and just irks me. I can respect the fact that maybe it doesn't matter to you, or perhaps you live in a state that doesn't allow a bayo lug.
2)I'm not real experieced in building AR weapons, but that I can tell, any marks or small drilling or even deep flats that are produced for your style FSB or my style FSB are going to be hidden underneath just about almost ANY style gas block or FSB you might choose to install in the future. Only a real FSB with taper pins will leave deep drill holes accross the barrel. But even those hole would be hidden under most gas blocks.
I did one, ground my own flats came out pretty good.
Just make sure to "measure twice and cut once"
Good luck
Bayonet lugs are HIGHLY over-rated. Speaking as someone who's done the bayonet assault course at Ft Knox (while enlisted), I can assure you, it'll be a LONG time before I choose to "affix bayonets" over any number of other commonly available weapons for home defense. ;) I'd probably grab my kid's baseball bat first. An M9 is more useful when not stuck on the end of a rifle.
So to address your real issue in this thread - take the damn thing to a machine shop and tell them you want flats milled into the barrel. Bring the FSB with you and expect to pay about 40 bucks.
If none of them will help you out, PM me and package the works up with a check and I'll do the job and return it to you for that same 40 bucks.
1) You do realize that the FSB you have (if it's like the photo in the link) is a non-bayo lug variety. At first my supplier tried to pawn off one of those on me, and I sent it right back. Though I will never attach a bayonette to my FSB, a neutered and politically correct FSB is something that I will spot right away and just irks me. I can respect the fact that maybe it doesn't matter to you, or perhaps you live in a state that doesn't allow a bayo lug.
I need a bayo lug about as bad as I need a place to mount a grenade launcher. I'll never have either one so provisions to mount them are worthless for me.
I need a bayo lug about as bad as I need a place to mount a grenade launcher. I'll never have either one so provisions to mount them are worthless for me.
Fair enough. Like I said in my post; I can respect that and understand it's a matter of personal taste.
There are so many better options than trying to dremel your barrel.
Just get a clamp on front sight and be done with it....don't hack your barrel half assing it with a dremel.....BTW I own a dremel and use it ALOT and what you wanting to do IS NOT A JOB for one....
There are so many better options than trying to dremel your barrel.
Just get a clamp on front sight and be done with it....don't hack your barrel half assing it with a dremel.....BTW I own a dremel and use it ALOT and what you wanting to do IS NOT A JOB for one....
Like a lot of folks on these boards that mention a particular part.......I already have it. Now is not the time to consider a different variety. These kinds of parts aren't cheap enough to just toss.
On more careful thought and preparation; I will not dremel it. I will install the FSB straight and use the existing screw holes in the FSB to make starter holes with a 1/16" drill bit. Then I will use a larger bit to drill holes large enough (3/32" ?) for the screws to lock into.
I now really don't envision this to be as difficult as the length of this thread might lead one to believe. If I don't like the results, then I suppose there will be no harm done putting these 4 little marks on the barrel where they don't show anyway. Then I could always send the barrel in to a smith to have this FSB or a pinned style FSB installed. As I'm not planning on reselling this barrel, these minor cosmetic drillings or marks (that don't even show) don't mean anything.
Thanks for the input.
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