o/t sighting in a rifle

johndeereman · Nov 26, 2010

well deer season starts here on monday took the trusty remington 270 win model 760 out to shoot today used this gun since i was 13 im 28 now never touched the scope well my question is i was shooting today to check it and im 3 inches low at approx 40 yards however i was shooting up a slight grade my qhestion is whats exceptable? where would i be at 100 yards or so?

Russ from MN · Nov 26, 2010

That sounds pretty bad, shooting uphill or downhill should make a rifle shoot high, I believe. You didn't say how much of an incline, I think it has to be a lot to make a difference, especially with a fast cartridge like a 270. My 308 shoots 2" high at 100 yds so very little allowance needs to be made up to about 250 yards. This year I hit a deer right in the top of the heart at 165 yds!

david - or · Nov 26, 2010

A slight grade will not matter.

3 inches low at 40 yards is not acceptable. Depending on the height of your scope the 40 yard point of impact should be between 0.5 inch low and 1 inch high to be zero at 100 yards and 200 yards respectively. Given a normal scope height of 1.5 inches and your report of 3 inches low at 40 yards this says your rifle barrel is aimed below horizontal. We'd expect it to be 6 or 7 inches low at 100 yards unless you adjust the scope.

MarkB_MI · Nov 26, 2010

Hmm. Three inches low? On a scoped rifle, the line of sight and the bullet's trajectory should be converging at that short distance; If the scope is, for example, 1.5 inches above the rifle bore, the point of impact should be within an inch of the point of aim at 40 yards.

Here's a very useful bullet drop calculator. You don't say what bullet you were shooting, but a 130 grain .270 bullet will have a muzzle velocity of around 3000 fps and a ballistic coefficient of about 0.44. Plugging in these numbers with a sight height of 1.5 inches, if sighted in at 100 yards you should be 0.4 inches low at 40 yards.
Handloads.com ballistic calculator.

MarkB_MI · Nov 26, 2010

Also, a little-known fact is that bullets will hit higher at a given range when shooting either uphill or downhill. So if anything your rifle would be shooting even lower if your range was level.

nickg · Nov 26, 2010

If your 3" low at only fourty yards be pretty tuff to get to a hundred.If you were three inches high you would be all right. I would try resighting it in at 40 and get it close to dead on. I like to sight my rifles in at 100yrds personaly.And my big rifles all have a bullet drop compensator in the scope which makes it a lot easier when I want to shoot past 100yrds. Id make sure that your scope is good and solid no loose screws and make sure your barrel and action are good and clean and try to resight it in. If you cant get a good group Id try a new scope. Banging around the woods and up and down the tree stands take there toll on scopes after a while.

johndeereman · Nov 26, 2010

im shooting 150 grain federals the traget was at best guess 2 feet higher than my shoulders i had a good group was just low guess ill get it back out sunday morning and try again got dark on me today thanks for your help

GordoSD · Nov 26, 2010

You need to bring it up to level at 40 yards. Then it"s imperative you get a 100 yard range. Then set it 2 inches high at 100. Then you will be about 2 inches high at 200 and 1/2 inch low at 300.

Gordo

MarkB_MI · Nov 26, 2010

150 grain bullet has a BC of .46 and has a muzzle velocity around 2800 fps in the .270 Winchester. Plugging those numbers along with a 1.5 inch sight height into the aforementioned ballistics calculator indicates the bullet should be .33 inches low at 40 yards to be zeroed at 100.

toadady · Nov 26, 2010

download http://www.huntingnut.com/index.php?name=PointBlank pointblank

Anonymous-0 · Nov 26, 2010

Every scope/rifle will be different with most of the difference being how high the scope is mounted above the axis of the bore. Most scopes adjust 1/4 inch for each click at 100 yards. . 4 inches low at 40 yards is probably 12 or so inches low at 100 yards. GordoSD ( I grew up hunting in ND) is right, if it was me I would crank in 10 clicks up and see where it hits at 100 yards. With a flat shooter like 270 I zero 2 1/2 inches high at 100 yards. Then forget about hold over, up slope down slope ect. out to about 325 yards. It dosen't matter to the deer if your heart lung is shot 3 inches high or 4 inches low. Wind will get you a long time before drop does. I suggest a internet search of Maximum Point Blank Range , or as we called it in the Army, Battle Zero. The only thing ever shot at 100 yards is paper. Most of the rest is from 30 feet to 300 yards. I like to pick a zero that will work for all.

GeneMO · Nov 26, 2010

The .270 is a flat shooting rifle. Are you hunting in open country or brush?

You can't really go wrong sighting the .270 in at 100 yards. If you were out in Wyoming or the Dakotas I would say 200 yards.

But here in the midwest (central MO) 100 is OK. At 100 yards, you will be an inch or so low at 200 yards.

Get a good solid rest. set up 100 yards back and fire 3 shots. draw a line to connect the three holes. Estimate the center. Adjust the scope accordingly. 1" low at 100 yards means 4 clicks up on most scopes.

If you are 3" low at 40 yards, you will be about 8" low at 100 and way off at 200.

Gene

TomH in PA · Nov 26, 2010

If you have a rifle vise (or improvise something to hold it steady while you adjust the scope) you can get it spot on with only one shot:

1) Carefully fire a shot directly at the bullseye of your target (no hold over or under, aim right for the spot)

2) Locate where the bullet struck the paper, make the hole easier to see with a sticker or marker it if you can't see it through the rifle scope

3) Lock the rifle in the vise and put the cross hairs back on the bullseye

3) Use the scope adjustments to move the crosshairs to where the bullet hit, being careful to not move the rifle

The scope is now adjusted to put the bullet right on the crosshairs

Mel in SW Iowa · Nov 26, 2010

Johndeereman, you have some excellent ballistic and sighting in observations, suggestions, and guidelines to go on here, but first you need to determine what caused a rifle and scope combination that was solid as a rock for 15 years to suddenly be this far off and fix that problem that might be a damaged barrel crown, loose stock/receiver screws, loosened up scope mounting blocks, scope rings, bent scope tube, or loosened optical elements inside of the scope. Your description saying it still groups well, leads me to believe you will find something bent or damaged, rather than something loose. As others have mentioned, most scopes will not adjust that far vertical. What brand, type (fixed or variable, hunting or target) , power scope are you talking about?
Good luck.

Sidekick · Nov 26, 2010

I agree. First look for loose or broken mounting hardware. I had this happen with my Mom's deer rifle a few years ago. Wouldn't group better than eight inches at fifty yards. The rear scope ring had a broken bolt and wasn't even connected to the mounts. If you can find a place to zero at 200 yards you won't ever be sorry. I know everyone says just have it hit two inches high at a hundred but you'd be surprised where that can put you at two hundred. Sometimes it's close and sometimes it's not.

gregk · Nov 26, 2010

Is the ammo the same as all of the other years? The reason I ask is that last year I missed four shots at deer that should have been hits and when I sat down to figure it out I found that I had grabbed a box of 150 grain bullets for my 30-06 instead of 165 that I usually use. This caused it to shoot over the back of the deer at 150 - 200 yards. I never checked at 40 yards but I'll guarantee it was off there too. just a thought

MarkB_MI · Nov 26, 2010

Greg, I'll bet in practice your 150 and 165 grain bullets impact very close to the same point at 150 yards. The 150s shoot a bit flatter, but the increased recoil of the heavier bullets will raise their point of impact.

Anonymous-0 · Nov 26, 2010

I admit to being rather picky about these things but in my 30-06 hunting rifles I can't even get 150 grain bullets from different manufactures to land close enough to the same POI to make me happy. In my 270, Sellier and Bellot 150 grainers land a good foot above 130 grain Federals at 100 yards.

MarkB_MI · Nov 27, 2010

Good point, Scott. It always puzzled me why someone would take a hunting trip without first going to the range with the ammo they intend to use. I suppose these same folks buy a lot of lottery tickets.

JBMac · Nov 27, 2010

I posted about missing a big buck a couple of weeks ago. Like you, my rifle is always spot on. I sure wish I had taken it and shot it before season began, I wouldnt have been posting about wounding and not finding a big buck. At 230 yds, the bullets I had used were 2 ft low and all over the place. My friend was cleaning out his safe and gave them to me. They were the same brand, style and grain as I always use. I tried a different, new box, and got the expected couple of inches low at 240 yds, with dinner plate sized grouping. At 100 yds it was driving tacks. I wont make that mistake again.

mEl · Nov 27, 2010

Hey JDMAN, At least we agree on what rifle to carry!!! mEl

Russ from MN · Nov 27, 2010

That is the system we use, saves a lot of ammo!

johndeereman · Nov 27, 2010

im using a bushnell 3x9 power here in penns woods hard to get a 100 yard shot let alone longer i try to hunt open ranges with it but you gotta go where the deer are so never know where im going to be

Anonymous-0 · Nov 27, 2010

Mark, that is how I won my stainless steel Ruger 338 mag with some European rangefinding 4 X 12 Scope. Some guy my cousin knows showed up with it at an Elk camp in Wyoming. It had never been shot but the gunsmith bore sighted it in or so claimed the braggart owner was making fun of my rifle, a Remington 721 in 270 with a Weaver 6X scope. A rifle and scope older than I am, that belonged to my grandfather, and I had been shooting since I was 12. So I made the bet, standing, 5 rounds each at 100, 200,300 and 400 yards. If I won I got his rifle and if he won he got my rifle and truck. With all that power and that big scope he couldn't see how he could lose. He went first, he never hit a target. My first and only shot hit 2 inches high at 100 yards. Even more fun than winning the rifle (so easy) was watching him get beat up, after the first 3 or 4 rounds all he would do is close his eyes and yank the triger. So now I have a 338 mag rifle, something I consider worthless. The 30-06 is big enough for anything in North America and the 338 mag is to small for Africa if I ever make it there. It came cheap enough though, one 130 grain Remington Bronze Point. Mr Braggart went to Walmart and bought some rifle scope combo, never shot, it an went hunting and never got anything. On the 3rd day I took a cow elk at 70 paces, one shot, fell in place. I recovered the bullet. As my elk hung on the pole Braggart explianed how my bullet failed because it didn't retain enough weight.

MarkB_MI · Nov 28, 2010

Scott, that's a great story. It never ceases to amaze me that the gunmakers are able to sell big magnums to guys who have no idea how painful they are to shoot, and how difficult it is to shoot them a second time without flinching. I don't do much hunting myself, but the friends I know who are successful hunters all stick to the tried and proven .30-06 or .270.

o/t sighting in a rifle

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