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Posted: 5/26/2010 4:34:56 PM EDT
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Can anyone explain the significance of the 3/6 and 4/8 markings on the rear sight elevation drum ?
Thanks, HRF |
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Maybe if I plug in a few numbers it will help to illustrate my confusion. Assuming a sight that is 2.75" above the bore axis; M855 ball zeroed at 25 yards will strike 10.46" high at 300 yards and 2.06" high at 400 yards. With a center chest hold on a 6 foot tall enemy, a bullet should stay on the target at either of these ranges (although at 300 yards it will be in the neck/chin area. The problem appears mostly at the greater distances. With the same sight/ammunition/zero, the bullet will drop 45.65" at 600 yards and 159.67" at 800 yards. That means our center chest hold at 600 yards might allow the bullet to strike the enemy in the foot if he doesn't move it during the .85 seconds it takes the bullet to get there. At 800 yards, the 13+ feet of drop means the enemy will be quite safe. Anyone info on this would be appreciated.
Thanks again, HRF |
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At the lowest setting, it means 300 meters, and when you crank it up one full turn, it means 600 meters (or 800 meters for a fixed carry handle). That position on the drum is marked twice. When you are engaging targets BEYOND 300 meters, you can dial up your range, 350m, 425m, etc., so you don't have to hold over.
PS: Check this out...it may help. |
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Quoted:
At the lowest setting, it means 300 meters, and when you crank it up one full turn, it means 600 meters (or 800 meters for a fixed carry handle). That position on the drum is marked twice. When you are engaging targets BEYOND 300 meters, you can dial up your range, 350m, 425m, etc., so you don't have to hold over. Exactly. You'd be surprised how much elevation a full rotation of the elevation drum gives you. 
OP, If you really want to know where your rifle shoots at a given range, you need to zero it and then shoot on a KD range. Develop your drop tables based upon what happens at the KD range. |
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Quoted:
Can anyone explain the significance of the 3/6 and 4/8 markings on the rear sight elevation drum ? Thanks, HRF The two sight apertures are not drilled on the sight plain, both in height and even side to side. The side to side part is due to as the aperture is flipped, it tracks the windage threads, and the different heights, that one should be able to figure out on your own (markings you are asking about). |
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Thanks for the info. This makes sense to me. When I was in the Marine Corps we were issued the M16A1 which did not have the rear elevation drum (elevation was adjusted with the front sight only). I currently shoot in High Power competitions with a RRA LARA2 National Match which has a rear sight drum graduated in .5 MOA clicks. So I was confused by the M4 markings. I guess I'm turning into an old guy.
Thanks Again, HRF |
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