Folks,
I use low magnification scopes for deer hunting such as 1.5, 2.5, and 4 power. I always feel limited by that power scope when I sight in my deer guns at 100 yards because I can't tell if it is the bullet choice or sight limitations that cause group size. Unfortunately for me, I'm left eye dominant but shoot right. Of course, accuracy could be based on technique and other variables, but let's just consider a 25 yard bench session for the sake of being able to clearly see the bulls eye through a low power scope.

I shoot 308, 35Rem, and 30-06 for deer. At 25 yards, where should I hit so that I am two inches high at 100? Once I find the best bullet choice, I'll practice at distance given that I have the best load for my gun. Also, I realize that the 35Rem will be a bit different due to its characteristics-the 30 cal's should be pretty much the same. If I remember correctly, an old timer gun-guru told me that 25 and 100 yards act as the same.

Is it safe to say that if I am off by 1" at 25, I'll be off by 4" at 100? A 2" inch group at 25 will be an 8" at 100?

Again, the purpose of this is to sight in the gun for proper bullet choice given limited bulls eye visibility with low power scope. Practice at distance comes later, but I have to know that what I am shooting is going to do its part.

What are your thoughts?

Thanks.

Welcome to the forum.

Dead-on at 25 is a good start, but it will depend on how high the scope is over the bore. I'd still test at 100, and FYI, I sight in just about everything 2" high at 100.

FYI your big game scopes are focused at a range of around 150 yards, generally. It'll give you eyestrain to shoot a lot at short ranges, and the parallax will be bad enough to cause errors.

If you want to reduce errors in sighting, experiment with different targets till you find one that is easy to line up the crosshairs on. Example, try making 4 squares into a larger square, say each of them 3" - 4" across and a couple inches apart, in a pattern. That will leave a white cross or plus sign, if you will, right in the middle of the target to lay your scope crosshairs in. Adjust for the reticle you have.

i dont know what to tell you, a trajectory goes through quite a wave during the first 100 yards, i think low at 25 would be high at 100 wouldnt, but ur doubling method is pretty false id say, try and sight the gun in to where u want it at 100 yards, and then get picky with loads and group sizs at 25 yards

Are your normal groups at 100 yards adequate to take deer cleanly? Are the 100 yd. groups under 4" center-to-center? If the answer is "yes" then adjust your low-power scope so that the center of the group is about 2" above the point of aim. You should be good to go.

With the .308 and the 30-06 why not just center your group on the point of aim at 100 yds. On deer you could then hold center out to about 200 yds. and out to 300 yds. aim just below the back line. In other words you can hold on hair all the way out to about 300 yards with a 100 yd. zero for those two cartridges.

Sighting in at 25 yards is only a start. You will still need to shoot at 100 yds. and preferably at whatever you think is your maximum yardage in order to truly know where your rifle hits at those ranges. Like most things in life, there are no shortcuts.

I concur, sighting in at 25 yards is not a substitute for shooting at longer ranges. I use that range only for preliminary sighting in of a rifle after mounting a new scope. At that range it is easier to get on target, even after bore sighting. The best that I can do is get the sights lined up for windage, and on point of aim. Depending on the rifle, scope, cartridge (and possibly the state of the moon), I have found that some rifles would then be several inches high at 100 yards, or low, but rarely on.
I use a lot of lower power scopes, including 2.5X and 4X. Use a proper sized target at 100 yards, with a large sighting mark, and you should have no problem getting good, and repeatable, groups at 100 yards. Don't try a little piece of 8 1/2 x 11 inch typing paper with a little dot.

We encourage all sighting-in shooters at our rifle range to start at 25 yds to begin with and to get the group dead center at that range. Then, when they move their targets out to 100 yds, they will normally group somewhere between 2" and 3" high, depending on the cartridge and loading. Most complete their sight-in and come back to verify that it was indeed, the case.

Most sight in charts recommend dead center for 25 yards. I set all my rifles at this sighting. All will be 1 to 2 inches high at 100 and be dead zero again at 250 yards. I never check the sighting at any other distance. Dead on 25 yards is dead on +/- 1.0 inch at 250 yards for .243, 25.06, .308, 30.06 and 7mm.08. This is with scope no more than 1.50 inches above line of sight.

Thanks a lot.
There is some difference of opinion, as expected, but I'm going to try and get the best group at 25 and then work from there. I'll try and find a target that works better for me-not sure what I'm using, got them at Wally World and they are for 100 yds, but target dot is fluorescent and I can't see it well due to the color washing out. Good ideas, and again, thanks for the input.

What most people who consider themselves to be quite informed on everything to do with shooting forget or don't even consider is that your sight-plane is a straight-line(a pulled string from your eye to your target)and your bullet starts below that line,then proceeds in a perfect geometric arc.

Here is a link which will most likely be quite useful too.

http://www.gunnersden.com/index.htm.sightin.html


George

The human eye is remarkably good at centering one thing in another. I bet you are not giving up as much as you think with your low powered scopes. You just need to find something that works to aim at.

Thanks a lot.
There is some difference of opinion, as expected, but I'm going to try and get the best group at 25 and then work from there. I'll try and find a target that works better for me-not sure what I'm using, got them at Wally World and they are for 100 yds, but target dot is fluorescent and I can't see it well due to the color washing out. Good ideas, and again, thanks for the input.

Those don't work so well for me, either, depending on the light. So it isn't just you.

Don't be afraid to make your own targets. Can of spray paint, make some templates out of a few of them, and see what works.

Load testing at 25 yards won't tell you much, I'm afraid. Bullets take a while to really settle down and a good group at 25 doesn't necessarily mean a good one at 100, or vice versa. You would be making sure you'll be on paper at 100, and perhaps weeding out the worst of them.

Even 50 or 75 yards would be a more useful test for centerfires, my opinion.

I agree with MikeG, at 25 yards any decent rifle should group in one ragged hole, just too close to sort out the good from the better loads. If you can't see well enough to hold on a black 6" bull on white paper at 100 yards, how are you going to hold on a grey animal in a grey background? You say you like low power scopes but if you can't shoot them why do you like them? Try a 3-9 variable, you can work up loads and sight in at higher power and turn it down to hunt if you like, but if the rifle fits you well and you become accustomed to shooting it you won't find higher magnification to be any handicap.

Thanks for the input, again.

Don't like big scopes because all of my shots are within 100 yards-don't need big glass, don't want to carry it. I can see a 6" black box from 100 yards and can put it in without too much problem. I can hit a pie plate from 100 yards without any problem, and that's good enough to kill a deer. My question had more to do with 1) a 25 yard zero and its ability to eliminate ammo that might be inaccurate, and 2)where to aim at 25 so that it's 2" high at 100. As expected, both pretty much covered.

I had 2 loads for my 358 that were both accurate, except they printed 8" apart at 100 yds. Couldn't tell that at 25 yds.