Fact/Fiction Sighting in

[Sigmar]

Initial sight in at 25 yards will put you on paper at 100. If you're shooting nickel groups at 25 what would the groups be at say 100 ?

[Chuck 100 yd]

Most center fire rifle cartridge guns will be on paper @100 yd if centered @25yd. TRUE

Generally you can expect the 100 yd group to be 4 times as large as the 25 yd. group.

What gun/caliber/ammo are you playing with?

[Sigmar]

Marlin 336 30-30 and AR 223/556

[AJMD429]

Depends on how big the 'paper' is...

Most guns if set up to launch the bullet to come up over the sight line around 25 yards, will have it 'coming back down' around 100 yards, though many may not, especially if the scope/sight height is rather tall - then the bullet may be headed so steeply 'up' that it won't be back down to cross line of sight until a few hundred yards.

Still, if I can't use my bore-laser to start out at 75 yards or so to start with, I'll "get on the dot" at 25 yards and generally TRY next at 100 yards. About 10% of the time it isn't on paper and I bring the target back to 50 yards, and sometimes it is WAY high at 50 even though on at 25.

Geometrically the 100 yard group should be four times the diameter of the 25 yard one (center to center of holes), but "wind" can increase the dispersion. However, though I'm not a good enough shot to demonstrate it, I have heard experienced shooters claim that the groups do NOT always expand thusly, and say it is because the bullets initially yaw or wobble or spiral or something, and later on "settle down" and fly more in a straight line.

Like I said, I'm not near a good-enough shot to ever see that phenomenon, though I've seen it happen with arrows shot from longbows....

[WyoShooter]

My groups are not much different at 200 yards than they are at 100 yards shooting from my .308 hunting/target rifle.

[sore shoulder]

Initial sight in at 25 yards will put you on paper at 100.

Yes.

If you're shooting nickel groups at 25 what would the groups be at say 100 ?

About 50 cents.

[Chuck 100 yd]

IF you are shooting one of those AR`s that has the scope mounted 4" or so above the bore line it can be anybodys guess where it will hit at 100. To be more apt to be on target at 100, sight it in a couple inches low at 25.

[sore shoulder]

IF you are shooting one of those AR`s that has the scope mounted 4" or so above the bore line it can be anybodys guess where it will hit at 100. To be more apt to be on target at 100, sight it in a couple inches low at 25.

My ballistic app has a field for line of sight above the bore.

AR irons are 2 1/2" above center of the bore. I have a carry handle mounted scope and it's 3 5/8" above center of bore.

The military sight in method for irons and CCO (red dot) is zero the weapon on a 25 meter target (this is regardless of whether it has a carry handle or flat top, since sight height is the same), which zeroes you for 300 meters, and puts you a few inches high in between depending where you're target is.

Now, according the ballistic calculator, with 55gr fmj and a 300yrd zero and 2.5 inches line of sight above bore, at 25yrds you will be .63 inches low, and at 100 yrds you will be 3.29 inches high.

Using a scope with line of sight of 3 5/8" above center of bore and 300 yrd zero, 100yrds will be 2.52" high and 25 yrds will be 1.7 inches low.

So your guess of "a couple inches" is pretty good.

[COSteve]

Done

[AJMD429]

The one 'good' thing about those ultra-high-line-of-sight scopes on AR's is that they enable (in theory) a bit wider range of yardages where you are 'point-blank', since they are closer to being parallel to the trajectory arc 'out there' vs. close-up. However when I ran that through my ballistic software to see if it really made much difference, I don't think it did unless your scope was about six inches from the bore axis...

[geobru]

Geometrically, the group should be 4x the size of the 25 yard group, but it depends on the type of sight you are using and how good your eyes are. I can't see as well at 100, so my groups vary with lighting and how I am seeing that day!