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Posted: 7/31/2003 2:30:17 PM EDT
[#1]
It's trigonometry. Assuming the line of sight on a rifle is level, the line of the bore has to be tilted up slightly in order for the bullet to cross the line of sight. The bullet's path will be a curve, since it starts out pointing slightly up, and gravity will pull it down.
The closer the line of sight is to the line of the bore, the greater the distance that the bullet's flightpath will be nearly tracking the line of sight. As you increase the height of the sights, the barrel has to be angled up further in order to get the bullet to cross the line of sight at the same distance (say 50m). Because of the increased angle, the path of the bullet won't be nearly as close to the line of sight. You can prove this by plugging numbers into a ballistic calculator. With everything else the same, and zeroing at 50m, calculate the difference from zero at 100m, 200m, and 400m with the height of the sights at 2". Run the same calculations with the height at 3", and note how much further from zero the bullet path is at 100m, 200m, and 400m. -Troy |
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Posted: 7/31/2003 5:37:39 PM EDT
[#2]
Quoted: It's trigonometry. Assuming the line of sight on a rifle is level, the line of the bore has to be tilted up slightly in order for the bullet to cross the line of sight. The bullet's path will be a curve, since it starts out pointing slightly up, and gravity will pull it down. The closer the line of sight is to the line of the bore, the greater the distance that the bullet's flightpath will be nearly tracking the line of sight. As you increase the height of the sights, the barrel has to be angled up further in order to get the bullet to cross the line of sight at the same distance (say 50m). Because of the increased angle, the path of the bullet won't be nearly as close to the line of sight. You can prove this by plugging numbers into a ballistic calculator. With everything else the same, and zeroing at 50m, calculate the difference from zero at 100m, 200m, and 400m with the height of the sights at 2". Run the same calculations with the height at 3", and note how much further from zero the bullet path is at 100m, 200m, and 400m. -Troy So, if I interpret what you said, then it IS best to have your sights closer to the barrel. If that is true then maybe someone else can answer the other question. [b]If lower is better, why didn't they design the rifle so that the irons could be closer to the bore?[/b] To add another question, why would you WANT your ACOG on a carry handle instead of on a flat top. |
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Posted: 8/1/2003 12:09:05 PM EDT
[#3]
Closer to the bore is better, yes, but there has to be SOME distance between the two, otherwise the barrel can't be angled enough to cause the bullet to cross the line of sight.
The gun requires higher (than typical on older guns) sights because the stock is straight. A straight stock significantly reduces muzzle flip, making it much easier to maintain muzzle control during full-auto or rapid semi-auto fire. Like everything in life, a gun is a compromise of many differing requirements, and getting a good balance is important to a rifle that will perform many roles well. The reason for placing an ACOG on a carry handle? Simple: because there are hundreds of thousands of ARs already that have carry handles. Flattops are relatively recent in the AR world, especially in the military. When the ACOGs were first designed, 95+% of all AR-based rifles in the military had carry-handle uppers. Given the CHOICE, your ACOG is best mounted on a flattop upper, of course. -Troy |
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Posted: 8/1/2003 12:27:30 PM EDT
[#4]
Quoted: A straight stock significantly reduces muzzle flip, making it much easier to maintain muzzle control during full-auto or rapid semi-auto fire. Thanks, that explains the straight stock question. But, on that note, couldn't the designers made a regular stock with a compensator on the barrel? Oh well, would have, should have, could have. Closer to the bore is better, yes, but there has to be SOME distance between the two, otherwise the barrel can't be angled enough to cause the bullet to cross the line of sight. I don't really agree with this. I have several guns with iron sights sitting right on the barrel (about as close as you can get) and they have no problem. |
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Posted: 8/1/2003 3:28:32 PM EDT
[#5]
First, no flame intended (for some strange reason I always come off sounding like some know-it-all jerk when I post, so my apologies in advance).
Second, Troy is correct. If you think about it, even where your sights are right on the barrel, the line of sight is still some distance above the line of the bore (the thickness of the barrel plus the height of the sights themselves). Troy is also correct when he says that the AR-15 is about compromises. Stoner could have designed the rifle with some drop in the stock so that sights could be lower, but decided instead for a design that would make the rifle inherently easier to control in rapid fire. You are certainly entitled to disagree with the design, and many do, but it is also important to understand the reasons behind he design before doing so. Again, no flame intended. Have a good weekend. I have to go shoot now. |
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Posted: 8/1/2003 3:28:51 PM EDT
[#6]
Those sights aren't in line with the bore, right? That's what I'm talking about. Sights need SOME elevation from the line of the bore, and the rear sight needs to be slightly higher than the front sight.
-Troy |
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Posted: 8/2/2003 1:29:48 PM EDT
[#7]
Quoted: Those sights aren't in line with the bore, right? That's what I'm talking about. Sights need SOME elevation from the line of the bore, and the rear sight needs to be slightly higher than the front sight. -Troy [:\] Please, don't get mad at this, but your original statement about needing SOME distance between bore and sights is unnecessary because no matter WHERE you mount a sight on a rifle you will have SOME distance between it and the bore, right? At least I can't think of any way to be looking straight down the middle of the bore to sight the rifle. Thanks again for the info you've provided on this topic. |
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