View Full Version : ok I'll ask... what's wrong with mounting your front sight on a rail? (no FSB)
I kind of stumbled into a gun with a rail mounted front sight. I'm running MBUS (front and rear), with the front sight mounted on a 12" midwest industries free float rail. I expected some sort of fairly tangible accuracy issues. If anything I've been quite impressed with how good the accuracy is. I'm not a bench rest shooter, and I don't think anyone else here is either....
I do plan to upgrade to a set of DD fixed sights soon, for duability, and because i think fold down sights are silly with no optic. (goin into point shoot mode! click click)
So what's so bad about this kind of setup? A quality fixed sight on a rail isn't going to break off or come loose. The other side i guess is gas blocks... I'm currently running a spikes set screw block... not the best setup, but there should be no issue with a pinned cut down sight or a good clamp on block.
just looking for opinions...
DeltaSierra
01-28-12, 21:10
Not sure if this will help or not, but it might be worth reading:
http://m4carbine.net/showthread.php?t=97461
militarymoron
01-28-12, 21:16
nothing wrong with it unless you put enough pressure on the rail or barrel while taking a shot, such that the front sight is no longer aligned with the barrel.
nothing wrong with it unless you put enough pressure on the rail or barrel while taking a shot, such that the front sight is no longer aligned with the barrel.
fair enough...
I guess i'm assuming the rail is perhaps more stiff than it really is.
I recall a guy asking what was so great about free float tubes, and it was again the same situation, applying pressure to standared handguards can flex the barrel. So i'm basically in a slightly better situation than someone without a free float tube. I'll take it.
I suppose in precision shooting it's worth noting that pressure on the handguard can change POA.
Purpose of the rifle is a big consideration. I run rail mounted sights on a few of my for fun rifles but unless if it is a scoped SPR type all of my working rifles will have a fixed and pinned front sight base. Back up irons are fixed again unless in an SPR type set up.
As MM mentions the issues of the rail mounted sights may come more into play when you start getting deflection on the rail which can cause a pretty good misalignment of the irons which is of course more noticeable as distance increases. Most don't test or even notice this because quite frankly many don't shoot enough in that configuration with just irons. Another thing to consider is that the weak link in the sight attachment may not be between the rail and the sight, but the issue might come between the connection of the rail and the weapon itself. I have seen enough rails move just enough from hard use to make it a concern. Same concept as to why many will suggest not bridging the gap between the upper and rail with an optic set up.
An Undocumented Worker
01-28-12, 22:40
If you use a shooting sling you can most definately induce enough flex to noticeably throw off the poi even at modest ranges, though realistically you would only use a tight sling at longer ranges which will make the pressure induced sight misalignment even more noticeable.
Purpose of the rifle is a big consideration. I run rail mounted sights on a few of my for fun rifles but unless if it is a scoped SPR type all of my working rifles will have a fixed and pinned front sight base. Back up irons are fixed again unless in an SPR type set up.
As MM mentions the issues of the rail mounted sights may come more into play when you start getting deflection on the rail which can cause a pretty good misalignment of the irons which is of course more noticeable as distance increases. Most don't test or even notice this because quite frankly many don't shoot enough in that configuration with just irons. Another thing to consider is that the weak link in the sight attachment may not be between the rail and the sight, but the issue might come between the connection of the rail and the weapon itself. I have seen enough rails move just enough from hard use to make it a concern. Same concept as to why many will suggest not bridging the gap between the upper and rail with an optic set up.
THIS and..
The two I have left have flip up. Have had no front sight issues...
That said, I was going to shoot today, and the right side of my Troy rear sight ear was bent. I forgot to flip it down last time I shot. My bad, yes. But it makes me wonder now...
Failure2Stop
01-29-12, 01:27
If it swivels, folds, screws, levers, or detaches it will have more potential failure points than one that is properly taper pinned to the barrel.
Belmont31R
01-29-12, 02:02
If you are using them as a BUIS (BACK UP) then you should not be concerned. With most modern quality main sights (RDS, 1-4x, high power variable) it would take a lot of damage or other failure to relegate yourself to the BUIS.
Anyways, no matter if if you have a pinned FSB like the typical A-frame or a rail mounted flip up they are subject to flex. The same holds true to nearly any firearm.
I do all of my shooting inside of 200 yards. 16" middy with a gov profile barrel.
I want to put a 12 o clock mounted x300 or TLR1 ahead of the front sight. that's part of the reason i picked up the long railed upper.
The concern i'd have with something like a daniel defense rail where the front sight block remains is heat around the light... those sights get toasty fast. If you're trying to operate a light around that it could be hazardous.
Optics are somewhere in the distant future for me, probably a basic aimpoint.
I do all of my shooting inside of 200 yards. 16" middy with a gov profile barrel.
I want to put a 12 o clock mounted x300 or TLR1 ahead of the front sight. that's part of the reason i picked up the long railed upper.
The concern i'd have with something like a daniel defense rail where the front sight block remains is heat around the light... those sights get toasty fast. If you're trying to operate a light around that it could be hazardous.
Optics are somewhere in the distant future for me, probably a basic aimpoint.
I put my light at 12 o'clock in front of my fsp on my dd fsp rail because that's what Larry vickers recommends. It works and I like it a lot. He shoots a lot more than you or I so I doubt it's a hazard.
you're talking about mounting a front sight on a free-float handguard, right? When people say "rails" I get confused as to what they mean as that's a pretty general term.
If you're talking about what I think you're talking about, nothing is wrong with it provided you understand the limitations. Attach a two-point sling at the front of the handguard and start using it as a shooting sling and you'll have problems. Zero off a bag and then shoot "real world" in monopod prone and you *could* have problems.
Most of these things are mitigated by the following:
For most people they are "backup" sights and 200 yard precision isn't their purpose
when combined with milsurp ammo and mil-type barrels the deviation can be hard to detect
most people can't shoot well enough to begin with to tell a difference
if you even just take the time to zero your "BUIS" you're already doing better than 90% of shooters that just slap them on there
Rob & Surf (or anyone else too) - How much would a monolithic upper like the VLTOR VIS or LMT MRP help with this issue/concern? I just put an order on a MRP and am just curious on your thoughts. I'm getting the MRP for it's other features, but the monolithic rail does interest me alot.
The rail/handguard connection on my DDM4 V5 with OmegaX is pretty solid, but some VERY slight rotational play. Not concerned about POI with BUIS, but I can see how it might cause POI shifts at distance, but like Rob said, I'm no where near precise enough at longer ranges, hell prob even as close at 100 yards, to notice much difference, if at all.
Once I have zero'd my irons, currently they are zeroes at 50 yards, I test them on a chest sized plate at about 250 yards. If I can make consistent hits on that, I'm happy.
I think it depends on the type of handguard one uses as well. One that is flimsy vs. very strong, and perhaps more importantly the anti-rotational properties of the handguard. Anti-rotation is an inherent characteristic of the monolithic upper.
I put my light at 12 o'clock in front of my fsp on my dd fsp rail because that's what Larry vickers recommends. It works and I like it a lot. He shoots a lot more than you or I so I doubt it's a hazard.
I do like that setup, but I feel like it's not without limitation. It doesn't take many rounds to get that front sight hot enough to cook fingers. I'm kind of a middy whore too, so that limits me.
you're talking about mounting a front sight on a free-float handguard, right? When people say "rails" I get confused as to what they mean as that's a pretty general term.
If you're talking about what I think you're talking about, nothing is wrong with it provided you understand the limitations. Attach a two-point sling at the front of the handguard and start using it as a shooting sling and you'll have problems. Zero off a bag and then shoot "real world" in monopod prone and you *could* have problems.
Most of these things are mitigated by the following:
For most people they are "backup" sights and 200 yard precision isn't their purpose
when combined with milsurp ammo and mil-type barrels the deviation can be hard to detect
most people can't shoot well enough to begin with to tell a difference
if you even just take the time to zero your "BUIS" you're already doing better than 90% of shooters that just slap them on there
yes, mounted on a midwest industries one piece free float rail. It seems to be a very stiff rail. i can't rotate it visibly.
I'm of the "light carbine" school of thought on AR15s as opposed to DMR or varminter. Like i said i've been quite happy with the accuracy. Not sure if i've grown as a marksman or what, but i shoot this much better than my last AR that had a fixed front sight and a bolt on carry handle rear sight. Probably all that pistol shooting i've done in the last 3 years has just smoothed out my trigger finger.
No issue. Should work quite well.
I hope this answers your question.
jonconsiglio
01-29-12, 17:55
Currently, all of my rifles have rail mounted sights. For a while I was running KAC URX II's and broke two front sights completely off since I kept them up most of the time. I now run KAC rail mounted sights on a RIS II and am running a DD fixed front on a 10.5" with a RIS II.
I've had no problems but they stay folded down now except on my 10.5" with the fixed front.
I still check my irons on occasion but most of my shooting is with Aimpoints or an ACOG. I think with the current quality of optics though, this isn't as big of a deal as it was 10 years ago.
I always run a folding rear since I sometimes run an ACOG and always keep the option of running a magnifier behind my Aimpoints.
I do like that setup, but I feel like it's not without limitation. It doesn't take many rounds to get that front sight hot enough to cook fingers. I'm kind of a middy whore too, so that limits me.
I have a Colt LE6920 that I installed an OmegaX 12.0 FSP rail on for the purpose of having the 12 o'clock mounted light (an X300).
Originally, I was concerned about the heat of the front sight, and the closeness of my fingers to said sight. Yes, the FSP gets really friggin' hot with sustained fire, but I take into account the fact that more likely than not, when I need to use the light, it will be to identify a potential threat before I fire any rounds, so heat from the FSP isn't a concern.
I'm hard pressed to envision a home defense scenario where I will be firing enough rounds (more than 20 or 30) to make the FSP so hot that it would be difficult or impossible to safely use the X300.
Other than that, I find the FSP-style rail to be a valuable asset, as it is much easier for me to drive the gun as opposed to having just a standard carbine length handguard.
I kind of stumbled into a gun with a rail mounted front sight. I'm running MBUS (front and rear), with the front sight mounted on a 12" midwest industries free float rail. I expected some sort of fairly tangible accuracy issues.
If you're getting any accuracy with those crappy sights, you're doing well. The limitation of those sights is a much bigger concern than having rail mounted front sights.
fair enough...
I guess i'm assuming the rail is perhaps more stiff than it really is.
I recall a guy asking what was so great about free float tubes, and it was again the same situation, applying pressure to standared handguards can flex the barrel. So i'm basically in a slightly better situation than someone without a free float tube. I'll take it.
I suppose in precision shooting it's worth noting that pressure on the handguard can change POA.
You can get a free float rail and keep the FSB. Then you get the best of both worlds. If rail space is an issue, get a gooseneck.
How many people here have experienced misses due to their front sight being mounted on a quality free-float rail? If so, at what ranges were those misses?
-B
How many people here have experienced misses due to their front sight being mounted on a quality free-float rail? If so, at what ranges were those misses?
That's hard to say. There's not really a control to confirm that it's the sight set up. It may be the sight radius, the accuracy of the gun, shooter error....
That said... I start to lose confidence in my rail mounted irons at about 300. The hits are just hard to get at that point and beyond. On the other hand. I'm able to hit out to 500 with an A2 rifle fairly consistently.
How many people here have experienced misses due to their front sight being mounted on a quality free-float rail? If so, at what ranges were those misses?
-B
Right?
If the guys worried about accuracy from the POSSIBLE slight movement of a front sight on a FF handguard then I'd assume he's not trying to hit a 12 inch target at 300+ yards. I would think he is trying to get nice groups. At least that seems like common sense to me.
But the points people made about folding sights breaking and requiring more time to deploy if needed seem very valid.
You can get a free float rail and keep the FSB. Then you get the best of both worlds. If rail space is an issue, get a gooseneck.
can you point me in the direction of what you mean by gooseneck?
Right?
If the guys worried about accuracy from the POSSIBLE slight movement of a front sight on a FF handguard then I'd assume he's not trying to hit a 12 inch target at 300+ yards. I would think he is trying to get nice groups. At least that seems like common sense to me.
But the points people made about folding sights breaking and requiring more time to deploy if needed seem very valid.
a 12" target at 300 yards would be perfectly acceptable for me. This i guess was more of a theory question than a "my gun isn't doing what i need it to" question.
Not to hijack but do you guys think the sight misalignment on a monolithic upper would be less possible than a bolted or however its attached free float rail.
can you point me in the direction of what you mean by gooseneck?
I'm guessing he means something like this:
http://stickman.rainierarms.com/galleries/Magpul%20V/STCK9114-1024-Stick.jpg
can you point me in the direction of what you mean by gooseneck?
This is the technical "gooseneck" as seen with the LaRue Tactical 11" Handguard SBRS (Gooseneck) LT15-11.
http://a248.e.akamai.net/origin-cdn.volusion.com/j4enh.r2en5/v/vspfiles/photos/BCM-URG%2011%20BFH%20LT11%20SBRS-2.jpg
http://a248.e.akamai.net/origin-cdn.volusion.com/j4enh.r2en5/v/vspfiles/photos/BCM-URG%2011%20BFH%20LT11%20SBRS-4.jpg
In the context of the suggestion, I believe a "cut-out" rail was meant, as shown in Brian1/75's post.
Which do you think would exhibit more heat on a light:
close proximity to the fsb
or
direct blast of burning gas from a flashhider?
I would submit that the muzzle blast of gas would be far more severe than heat radiation from close proximity to the FSB. I've been running a Surefire 6PX @ 11 o clock with the bezel extended just slightly beyond the FH, so it's getting quite a bit of blast. The highest volume of fire it's seen has been 500+ rnds in one day at a Vickers class. The light still runs like a champ!
As far as FSP vs flips, I run KAC's on a 14.0 DD Lite rail. Nice long sight radius, but they go away when running my T1. I prefer the un-cluttered sight picture. Before anyone asks, yes, I do practice with those irons. In fact, I ran that whole Vickers class with the KAC irons because I didn't have the T-1 yet. No issues, and I was one oof the top shooters in the class both for speed and accuracy.
Which do you think would exhibit more heat on a light:
close proximity to the fsb
or
direct blast of burning gas from a flashhider?
I would submit that the muzzle blast of gas would be far more severe than heat radiation from close proximity to the FSB. I've been running a Surefire 6PX @ 11 o clock with the bezel extended just slightly beyond the FH, so it's getting quite a bit of blast. The highest volume of fire it's seen has been 500+ rnds in one day at a Vickers class. The light still runs like a champ!
As far as FSP vs flips, I run KAC's on a 14.0 DD Lite rail. Nice long sight radius, but they go away when running my T1. I prefer the un-cluttered sight picture. Before anyone asks, yes, I do practice with those irons. In fact, I ran that whole Vickers class with the KAC irons because I didn't have the T-1 yet. No issues, and I was one oof the top shooters in the class both for speed and accuracy.
I don't think heat in either of those cases should be an issue. I wouldn't mount a light directly to a railed gas block, but other than that a quality light should be fine.
having it close to the muzzle will dirty the lense fast. consider that something like an X300 is designed to be mounted in very close proximity to a handgun muzzle, so being mounted slightly further from a rifle muzzle should be ok.
I do all of my shooting inside of 200 yards. 16" middy with a gov profile barrel.
I want to put a 12 o clock mounted x300 or TLR1 ahead of the front sight. that's part of the reason i picked up the long railed upper.
The concern i'd have with something like a daniel defense rail where the front sight block remains is heat around the light... those sights get toasty fast. If you're trying to operate a light around that it could be hazardous.
Optics are somewhere in the distant future for me, probably a basic aimpoint.
I was responding to this post you made. Here's my light, it wipes clean with a finger or cloth.
As you can see, it's a non-issue:
http://i854.photobucket.com/albums/ab104/ASH556/IMG_73261.jpg
http://i854.photobucket.com/albums/ab104/ASH556/IMG_73301.jpg
That's hard to say. There's not really a control to confirm that it's the sight set up. It may be the sight radius, the accuracy of the gun, shooter error....
That said... I start to lose confidence in my rail mounted irons at about 300. The hits are just hard to get at that point and beyond. On the other hand. I'm able to hit out to 500 with an A2 rifle fairly consistently.
Confirming how much rail flex influences POI is fairly easy to measure, as long as the shooter is up to snuff. I'm not there (not by a long shot, no pun intended), which is why I'm asking better shooters than I if they've experienced this.
-B
I was responding to this post you made. Here's my light, it wipes clean with a finger or cloth.
As you can see, it's a non-issue:
http://i854.photobucket.com/albums/ab104/ASH556/IMG_73261.jpg
http://i854.photobucket.com/albums/ab104/ASH556/IMG_73301.jpg
ooh ok, i wasn't concerned for the light, i was concerned with putting my fingers on the sight block. those things get warm after a half a mag or so. I guess gloves are an option, I just would prefer to keep my rifle as friendly as possible on my end of it.
ooh ok, i wasn't concerned for the light, i was concerned with putting my fingers on the sight block. those things get warm after a half a mag or so. I guess gloves are an option, I just would prefer to keep my rifle as friendly as possible on my end of it.
10-4, gotcha now.
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