View Full Version : Midlength barrel with non-F-marked FSB
I picked up a midlength 16" barrel recently from a well respected manufacturer and was a little surprised to find out that the pinned FSB on it was not f-marked. I haven't measured yet to verify the height, but assuming that it isn't the f-marked height, does that mean that the fsb is incompatible with flat top mounted sights (Troy in this case)?
Thanks in advance for any help.
If you run out of adjustment you can always replace the sight post with a taller one.
citizensoldier16
03-06-13, 20:52
If you run out of adjustment you can always replace the sight post with a taller one.
Exactly.
uncle money bags
03-06-13, 21:03
Sooooo, who is the manufacturer?
Wrong. If its not made right, its not made right. Simple as that.
If you run out of adjustment you can always replace the sight post with a taller one.
citizensoldier16
03-06-13, 23:09
Wrong. If its not made right, its not made right. Simple as that.
With deep respect Iraqgunz, I believe that replacing a sight post is easier than replacing a FSB. While the rifle was, indeed, made incorrectly...the solutions for the end user are:
a) send the rifle back and wait
b) replace the FSB with the correct F-marked one
c) install a taller sight post
While operators such as yourself and others on this forum would argue that option A is the most appropriate...option C is also viable for the civilian shooter.
I'm not saying you're wrong...on the contrary, you're absolutely right. I am merely supplying the OP with a remedy that is easily completed.
Iraqgunz, you are a wealth of information...from which I have gleaned untold amounts of knowledge. I have no grudge with you, or your advice. As I said, ultimately, you are absolutely right.
However, if the OP is just using his AR for range use or casual shooting, replacing the post is easier.
Op i have seen some front site bases that were not market, but they were the proper height. The first thing you need to do is measure it. It should be 1.98 inches from the top of the barrel to the flat area where the post threads into. Im almost positive that number is right, but someone will correct me if Im wrong.
If it is the wrong size just replace it. Regardless if it is a range gun. There is a right way to do things, and if it is one of the companies that are highly regarded by this forum. It will be in a timely manner as well. To replace the fsb should take no time unless the company is out of fsb's, but they should give you a rough estimate of the time it will take to remedy the situation.
Yes, I understand that. But, this is why trash peddlers have been able to survive. Because people to know that they didn't know and then once they did they didn't force the issue. Had that been happening companies would have figured out it was cheaper to do it correct the first time or they would have been impacted financially or their name would have been shit.
I was contacted by a police agency in Australia that purchased Remington R4 carbines and they are having issues because they are using Magpul rear sights and Aimpoint Comp M2's and they can't get a proper zero with their non F-marked FSB's.
Now they have to get taller posts, but they are concerned about officers damaging them because the posts will stick up out of the protective wings.
In the OP's case he has purchased a barrel only. So I would contact that company and tell them to make it right.
With deep respect Iraqgunz, I believe that replacing a sight post is easier than replacing a FSB. While the rifle was, indeed, made incorrectly...the solutions for the end user are:
a) send the rifle back and wait
b) replace the FSB with the correct F-marked one
c) install a taller sight post
While operators such as yourself and others on this forum would argue that option A is the most appropriate...option C is also viable for the civilian shooter.
I'm not saying you're wrong...on the contrary, you're absolutely right. I am merely supplying the OP with a remedy that is easily completed.
Iraqgunz, you are a wealth of information...from which I have gleaned untold amounts of knowledge. I have no grudge with you, or your advice. As I said, ultimately, you are absolutely right.
However, if the OP is just using his AR for range use or casual shooting, replacing the post is easier.
You can't just replace them because each barrel is drilled and pinned separately which means that depending on how it was made it could be canted or the holes for the FSB pins will not line up right.
Op i have seen some front site bases that were not market, but they were the proper height. The first thing you need to do is measure it. It should be 1.98 inches from the top of the barrel to the flat area where the post threads into. Im almost positive that number is right, but someone will correct me if Im wrong.
If it is the wrong size just replace it. Regardless if it is a range gun. There is a right way to do things, and if it is one of the companies that are highly regarded by this forum. It will be in a timely manner as well. To replace the fsb should take no time unless the company is out of fsb's, but they should give you a rough estimate of the time it will take to remedy the situation.
I think its possible the op either didn't notice in the ad which version of the front sight came with the barrel, or perhaps the vendor didn't make that information clear. In this case not right for the op does not necessarily mean manufacturer fault.
How did you reach this conclusion since he hasn't told us yet who makes the barrel?
You do realize that Bushmaster for example put non F-marked bases on almost all of their AR's over the years, right?
I think its possible the op either didn't notice in the ad which version of the front sight came with the barrel, or perhaps the vendor didn't make that information clear. In this case not right for the op does not necessarily mean manufacturer fault.
I reached no conclusion. I only offered an alternate posibility.
I appreciate everyone's input. I plan on measuring the base when i get home from work today.
I tend to agree with Iraqgunz: I paid a decent amount for the barrel and expect to get something made to the right specs. Today's standard is flat topped receivers. Additionally, its my understanding that installing a new FSB is not possible, at least not without the exact original fixture and drill settings. Generally, taper pins holes do not seem to be drilled to an exact spec and are often drilled to different depths and at different angles.
If it is not the F-marked height, i plan on addressing it with the manufacturer. The ad for the barrel is not specific relative to the FSB, but on their website, ads for their full carbines all state that F-marked FSBs are used. A reasonable person would assume that a barrel assembly would come with the same (again, it is the contemporary standard for well made AR parts)
Re: the name of the manufacturer, i think its only prudent to hold off on mentioning their name until after I A) verify the height and B) contact them.
Thanks again for the help.
You do realize that Bushmaster for example put non F-marked bases on almost all of their AR's over the years, right?
Don't some of these companies also supply the taller post with the non-F marked bases so the weapon will at least zero? Even if its "wrong".
JBecker 72
03-07-13, 12:06
Dude, I am actually looking for a mid length barrel with a non F marked front sight post to accompany the A2 upper I have here. Please pm me with details.
Not always. The Remingtons I mentioned were sold with the carry handle and changed by that agency. They were unaware of the difference and the front sight post was a standard height.
I have seen BM carbines that had standard front sight posts in them from the factory.
Don't some of these companies also supply the taller post with the non-F marked bases so the weapon will at least zero? Even if its "wrong".
You can't just replace them because each barrel is drilled and pinned separately which means that depending on how it was made it could be canted or the holes for the FSB pins will not line up right.
My mistake they all look the same so i forget the pits have to be drilled for each base. I would wory about the taller pin just like the department from Australia you referred to.
In this situation what would you do if the situation was not remedied by the manufacturer? If you don't mind elaborating on what you would do in a situation such as this.
Im interested to hear how you would handle this situation. I have an idea of what i would do in this case, and i wonder if Im in the ballpark.
I can't say since I don't know who the manufacturer is. Plus we all have different tastes. Since I have a few FSB carbines/rifles I would put a low pro on it and move on.
My mistake they all look the same so i forget the pits have to be drilled for each base. I would wory about the taller pin just like the department from Australia you referred to.
In this situation what would you do if the situation was not remedied by the manufacturer? If you don't mind elaborating on what you would do in a situation such as this.
Im interested to hear how you would handle this situation. I have an idea of what i would do in this case, and i wonder if Im in the ballpark.
What about the Colt 6720's. They do not have a F marked FSB. Do they need to be sent back to Colt and replaced ??
I can't say since I don't know who the manufacturer is. Plus we all have different tastes. Since I have a few FSB carbines/rifles I would put a low pro on it and move on.
Can it be drilled again for a new fsb or would that be removing to much material? Sorry for the stupid question.
Go ask Colt.
What about the Colt 6720's. They do not have a F marked FSB. Do they need to be sent back to Colt and replaced ??
Go ask Colt.
What kind of answer is that ??????
A flippant one.
He's referring to the fact that Colt owns the design spec so it is whatever they say it is even if they were to specify something that didn't work (not that they would.)
It sounds like it is as I suggested. The op bought a barrel with the incorrect assumption that the front sight would be correct for his application. Just because it's incorrect for his, or even most applications doesn't mean that there aren't guns this barrel would be properly specced for. Hence, not the manufacturer's fault that the op bought the wrong item.
diving dave
03-09-13, 10:23
The PD I work for purchased rifles for use at our airport PD division, and we had the same issue. Flat top receivers and non F stamp front sights. Some of the rifles during zeroing had the front sight post so high it looked like they were about to pop out....Not sure they ever fixed the issue, I dumped mine and bought a Colt 6920.
I have a buddy who shoots a DPMS with non-F-marked FSB. He did replace his rear BUIS with a Troy. It wouldn't sight in for elevation. We ended up just replacing the front sight post with a taller one (which DPMS sells on their web site http://www.dpmsinc.com/Front-Sight-Posts_c_248.html). That has worked out fine.
From GotM4
http://img.photobucket.com/albums/v408/gotm4/556pics/FshelfColt.jpg
It sounds like it is as I suggested. The op bought a barrel with the incorrect assumption that the front sight would be correct for his application. Just because it's incorrect for his, or even most applications doesn't mean that there aren't guns this barrel would be properly specced for. Hence, not the manufacturer's fault that the op bought the wrong item.
As I stated, their complete rifles are all carry f-marked FSBs on their website. Its a reasonable assumption to think that their barrels would come with the same. The ad for the barrel was not specific. Did I assume and should I have asked before buying, sure - but > 95% of all ARs on the market today are flattops.
Am I going to ask the manufacturer to either swap it out or provide a another barrel with an f-marked FSB, yes. I feel this is a reasonable request.
I'm not judging you for it. I bet it happens all the time and like Iraqgunz said, most people probably don't press the manufacturer or the vendor to help resolve the problem so the vendors get lazy about clarifying it in the product listing. It would be proper customer service for the vendor to allow a return or exchange, but the product is not built wrong just because of the fsb.
Straight Shooter
03-09-13, 23:47
My LMT carbine isnt F marked, but its GTG.
My LMT carbine isnt F marked, but its GTG.
thanks for the comment, just purchased an LMT upper for a friends build and noticed the FSB was not F marked.
Go ask Colt.
I just thought that I would ask the experts around here, but I get a typical smart a-- answer.
I just thought that I would ask the experts around here, but I get a typical smart a-- answer.
I was going to ask the same question. I briefly had a 6720 upper that shot way high and I refuse to have a sight post tall enough to get that thing to zero. I should have researched that model more before I bought it, but I made an assumption and got bit...
You know the drill. If Colt ****s up, you obviously need more training. Or you should use the orange search button. And this is not Facebook. Contact the manufacturer.
An update: Heard back from the manufacturer. They said that despite the fsb not being marked, it would be gtg. Finally got it assembled and took it to the range yesterday. Got a good zero @ 50 yd with M855. Thumbs up.
Happy Easter.
An update: Heard back from the manufacturer. They said that despite the fsb not being marked, it would be gtg. Finally got it assembled and took it to the range yesterday. Got a good zero @ 50 yd with M855. Thumbs up.
Happy Easter.
good to hear it all worked out for you, the rifle I just put together for my buddy has an LMT upper with a non F marked FBS. H put a rear troy flip down sight on it then I went and sighted it in on Friday while he had to work. Everything was good to go.
Did you have to unscrew the front post much to achieve that, gt5966b? Or is the post still close to mechanical zero (indicating the FSB is proper height)?
Anyway I think it's important to quote what Iraqgunz said a while back because it's so true. As he pointed out Remington (then later he pointed out Bushmaster) use the wrong height FSB on their A4 receivers expecting no one will complain. Usually few do so they get away with it. So don't take the manufacturer's GTG claim unless it really is GTG.
This practice goes beyond Remington and Bushamster - DPMS, ArmaLite and RRA do it as well. I had an ArmaLite upper that I had to back out the front sight where it wobbled to get it to zero. I then got a 0.04" taller front sight post which solved that issue but as IG said the post stuck out above the protective wings and was a worry to me. I finally traded off the upper and got a Daniel Defense (that guess what - had an F-marked FSB in the first place).
Yes, I understand that. But, this is why trash peddlers have been able to survive. Because people to know that they didn't know and then once they did they didn't force the issue. Had that been happening companies would have figured out it was cheaper to do it correct the first time or they would have been impacted financially or their name would have been shit.
I was contacted by a police agency in Australia that purchased Remington R4 carbines and they are having issues because they are using Magpul rear sights and Aimpoint Comp M2's and they can't get a proper zero with their non F-marked FSB's.
Now they have to get taller posts, but they are concerned about officers damaging them because the posts will stick up out of the protective wings.
In the OP's case he has purchased a barrel only. So I would contact that company and tell them to make it right.
Did you have to unscrew the front post much to achieve that, gt5966b? Or is the post still close to mechanical zero (indicating the FSB is proper height)?
doesn't seem too bad, but i'm not an expert. I would be interested to hear others' opinions.
http://imageshack.us/a/img46/7863/imageicxe.jpg
michael word
03-31-13, 14:31
That is not a F-marked hight front sight and would get the taller post to lower the bottom of the flat surface for better support of the sight post.
That is not a F-marked hight front sight and would get the taller post to lower the bottom of the flat surface for better support of the sight post.
well that sux.
Yeah that's definitely an A2 height FSB which would be fine if the barrel had been installed in an A2 upper, not a flat top. I had to unscrew my ArmaLite post even further to zero at 100 yards and it flopped around. I'm fairly sure you would too if zeroing at 100 yards. You might want to try that to have more points to make if you take on the manufacturer.
If the manufacturer advertised an F-marked FSB then what showed up at your door should have been right. That definitely is not GTG except on an A2 upper. If nothing else they should knock something off the price to help you out.
Did you have to unscrew the front post much to achieve that, gt5966b? Or is the post still close to mechanical zero (indicating the FSB is proper height)?
Anyway I think it's important to quote what Iraqgunz said a while back because it's so true. As he pointed out Remington (then later he pointed out Bushmaster) use the wrong height FSB on their A4 receivers expecting no one will complain.
I agree completely the correct way is to have a F marked FSB or at the very least come with the taller front sight post.
However, perhaps they use the "wrong" FSB because they actually DO have very few that complain? We have 12 bushmaster carbines at work and everyone of them are sighted in at 50/200 zero. None have the taller front sight post and none of them (while they do stick out some) extend past the ears or "wobble" around.
In this case, I'd get the taller Front sight post and be done with it. I like my front sight to be as close to mechanical zero as possible.... It'd drive me nuts sticking out that far from the FSB.
I think many of the "comspec" AR makers like ArmaLite and Bushmaster who have been around 20 years or so just continued using the A2 FSB even though they saw increased sales over the years of flat top receivers and decreased sales of A2 receivers. To offset zeroing issues they sold rear sights/carry handles that also were A2 height (.04" shorter).
Today the vast majority of receivers are flat top/A4 and most rear sights are A4 height yet the comspec makers hold on to the A2 FSB probably not to confuse and anger their customers. They just hope no one will notice, and usually people let them get away with it.
Anyway, it's not right and no one buying a new rifle today should have to put up with this crap. And when selling a barrel with FSB, the vendor should clearly state A2 or F-marked.
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