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Posted: 1/1/2006 10:27:10 AM EDT
[#1]
They make a taller front sight post for ARMS-40's, Colt removeable carry handles, etc. Bushmaster and DPMS sell them.
After I zero at 50 yards, I fine tune it at 100, 150 and 200 meters until I get it close enough. I don't mind being an inch high here and a inch low there. If you only have access to 50 and 100 yards you can still do some tweaking with your zero but I would get a taller front sight post first. I don't know if your problem has anything to do with using the large apeture or not. I only use the small one. |
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Posted: 1/1/2006 11:41:48 AM EDT
[#2]
The two apertures are battle, and long range (reason for the nuber stamped on the smaller aperture).
Starting off with the battle sight, your zero should be 100 yards. Sighting in shorter than this means that you are forcing the sights to look more downward than needed, and when you aim the rifle out to 100 with the 50 yard zero, it's going to shoot high. So, zero the rifle out for the 100 yards (allows you to use the rear elevation knob settings correctly), then if you need to shoot at a shorter distance of around 50 yards, click the elevation knob up to around the 400 yard mark to make the sights look the more downward plain needed for the correct front sight post hold. Note: For a 100 yard zero, click the rear sight all the way down, then come back up three clicks and set the knob number to 1/3 via the set screw, and then adjust the front post to zero out the sights for the 100 using the large aperture. |
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Posted: 1/1/2006 7:25:09 PM EDT
[#3]
This isn't a typical A2 sight. The rear sight only has 2 apertures for range, a long and a "battle" aparently. I would have thought a gun requiring a taller post would have come with it but I guess I'm wrong...
So, does this mean I MUST buy a front sight post before I can get it to zero at 100 yards (considering it's still shooting 5" high)? |
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Posted: 1/1/2006 8:24:19 PM EDT
[#4]
I guess you could try zeroing with the small apeture or aim low but I would get the new front sight.Taller front sight
Notice how it says this sight should be used with the ARMS 40. |
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Posted: 1/2/2006 12:31:57 AM EDT
[#5]
not just the ARMS sights but any USGI sight mounted on a USGI flattop that doesn't use an FSB of the correct height
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Posted: 1/2/2006 9:54:40 AM EDT
[#6]
Well now to complicate things I did some further research and it apears that the taller post is only needed if you do not have the F marked front sight base. My gun did come with this front sight base...
I think I'm going to totally rezero everything (crank post all the way flush, 100 yard zero, ect...) and see if I still have problems. My dot sight is on it's way so I don't think I'll be using the irons much after that but I want to have them in case I need them. All this being said, if I zero at 100 yards, how high will I be at 50? I don't want it to be more than a few inches if possible... So another question: If I already have an F marked FSB, why do I need the taller post? |
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Posted: 1/2/2006 2:08:41 PM EDT
[#7]
At a 100 zero, your going to be few inches low at 50.
To correct, crank the rear sight up to around 3 or 4 to solve the problem (make the sights look more downward). |
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Posted: 1/2/2006 2:09:28 PM EDT
[#8]
is this a COLT?
does the F look like this? 
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Posted: 1/2/2006 3:45:14 PM EDT
[#9]
To clarify things...
The gun is a STAG M4 profile, the FSB has the 'F' mark (meaning for 'F'lat-top yes?), the rear sight does not have ANY elevation controls what so ever, it is a ARMS 40A2 style bui. I can't crank any elevation out of the rear sight because it can only adjust windage. |
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Posted: 1/2/2006 7:57:22 PM EDT
[#10]
 
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Posted: 1/3/2006 1:47:34 PM EDT
[#11]
The measurement of where your arrows are pointing (I'm assuming from the bottom of the upper to the "valley" of the picatinny rail) is 1 and 11/16 of an inch.
Is there anything else I should measure? |
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Posted: 1/3/2006 2:21:17 PM EDT
[#12]
the height from the bore to the "UP" marked flat on the FSB is also good to check
do you have calipers? you're looking for ~ 1.720" on the upper as shown, 1.840" bottom to top |
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Posted: 1/3/2006 3:27:38 PM EDT
[#13]
I'll take it over to the neighbors house to see if I can get you some more measurements.
I was looking at the barrel with the handguards off and it could just be an illusion but my barrel looks slightly bent upward. I HIGHLY doubt this is the case but maybe that is my problem. |
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Posted: 1/3/2006 3:51:08 PM EDT
[#14]
a bend is fairly easy to see, sight down the bore on a slightly bright background and aline the concentric circles you see in the bore, if you can't aline them or they shift when you slowly rotate the barrel in your hands then the barrel is most likely bent.
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Posted: 1/3/2006 4:22:16 PM EDT
[#15]
No luck on the neighbor. I re-measured the upper and my measurements are very close to what you have. I looked at the picture of the two FSBs you posted. My FSB is definately marked 'F' so is it normal for the shooter to have to raise up the front post as high as it is in your picture?
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Posted: 1/3/2006 4:31:53 PM EDT
[#16]
I looked down the bore and I think I might actually have a bent barrel. No matter how well I center the "rings" created by looking down the barrel, there is always somewhat of a shadow on the "top". That being said if I flip the upper upside down I see the shadow on the lower portion.
Does this sound like a bent barrel? |
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Posted: 1/3/2006 6:04:36 PM EDT
[#17]
It's official, bent barrel. Had 2 other people look at it and compared it to another AR 15 upper. Definately bent...
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Posted: 1/3/2006 6:18:28 PM EDT
[#18]
sounds like it's time to send it home, whose is it?
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Posted: 1/3/2006 7:18:56 PM EDT
[#19]
Stag M4 profile upper on top of a Stag lower.
I'm not to worried about it, from what I've heard Stag is a good company who I doubt will have any problems standing behind something like this. It's pretty obvious that it was just a bent barrel from the time it was made. The packing material was fine, gun has no marks on it, gas tube is perfect. Probably just 1 in a 1000. |
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Posted: 1/3/2006 8:01:11 PM EDT
[#20]
odd that it's bent straight up but can happen
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Posted: 1/28/2006 3:51:30 PM EDT
[#21]
Dangasaur, sent you an I.M.
Having the same problem with my new Stag M4 |
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Posted: 2/1/2006 3:38:19 PM EDT
[#22]
I think a 50 yard zero will shoot high at 100. 50 and 200 are the same POI. So, the bullet is on the rise at 100 yds., and above the POI for a 200 yard placement.
Do I have this correct? I think I do. Tack |
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Posted: 2/2/2006 4:26:44 AM EDT
[#23]
Dead on on the idea, but the bullet never rises up from it's path, it's the down ward sight plain that intersects the bullet path at the two marks as the bullet is dropping to earth due to gravity. Kind of like changing in the sights does not make the barrel shoot the bullet any different in regards to it POI, only zeroing is makes the sights look where the barrel is sending the bullets. 
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Posted: 2/2/2006 4:28:26 AM EDT
[#24]
In regards to the barrel being bent, you really need to pull the barrel to confirm.
It could be that the upper was milled wrong, and the upper barrel socket is out of spec. |
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Posted: 2/3/2006 8:36:07 PM EDT
[#25]
tacks right. this is a simple explanation.
www.bobtuley.com/external.htm |
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Posted: 2/4/2006 12:49:58 AM EDT
[#26]
From the point that the bullet leaves the barrel, gravity is pulling the bullet down, even if the shot is at an upward angle. Since gravity is a constant, then the bullet drop per flight time is a constant as well. In regards to a bullet curve, it is nothing more than the constant drop of the bullet (time in flight), by the amount of distance the bullet travels in regards to speed (FPS). This means as the bullet slows down due to resistance (air), the drop will be greater, hence a more stepper shape curve downward. I think this was covered a while back, but no bullet has aerodynamic lift capability, hence it never rises from the original bore line flight patch, but begins to drop from the pull of gravity once it leaves the muzzle (even shot at a upward angle). |
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Posted: 2/4/2006 1:43:10 AM EDT
[#27]
the sightline is the straight line to the target, not the boreline. the bullet is not on the rise relative to the boreline, but is to the sightline.
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Posted: 2/4/2006 11:50:27 AM EDT
[#28]
Infsqdldr, no worries!!!
We are both talking about the same thing. Myself, I just refer to the barrel bore line/bullet flight path as the constant, and the sights adjusted to look down to intersect the bullet path at any given point to make the POI and the POA the same point (sights being the variable). Even when the bullet is path arched upwards to compensate for the drop, gravity is still pulling the bullet down. Where the variable comes into play with the bullet being under or over the sight plain is the height distance of the sights over the bore (and how the sights are adjusted), and this creates the two different Zero points (higher sight plain over bore will result in longer distances/ greater above or below between the two given zero points). Referring to the sight plain as the constant, may lead people on to believe that changing the sights does in fact change the flight path of the bullet (bore flight path), and as long as we all agree that the changing the sights does not change the bullets flight path out of the barrel in any way, I think that we can let this one go.
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Posted: 2/4/2006 2:31:36 PM EDT
[#29]
roger that. sorry for the confusion. damn semantics. cheers.
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Posted: 2/5/2006 9:07:56 AM EDT
[#30]
First, with the ARMS 40 type buis you will need the taller front sight post. More importantly, you should always set BZO (battle sight zero) using the small long range appeture. The larger "Battle" appeture is used at shorter ranges to pick up targets more quickly. If you zero with the small app, your groups afterwards should be good with either appeture. Good luck with the bent barrel though. John |
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