OK, for those of you with a head for these numbers......
I just bought a rifle for my son - Remington 7600 .243. Went to sight it in. At 25 yards, it was 3" low (dead center, just low). Using 100 grain Core Lokt rounds.
I re-zeroed in at 25 yards, so I know it will be about 3" high from 100-220 yards, then zero again at 250.
Assuming the rifle was on-target from whoever sighted it in previously, what would the zeros be - I can't reverse-engineer the numbers.
Thank you everyone for contributing.
Paddle - where I hunt I have visibility out to 200 yards. That said, the farthest shot I've ever taken from that stand (over 20 years) is 150.
Personally, I've used the same gun (Rem 270 7600), same ammo (Rem Core Lokt 130gr), the entire time.
I was just curious to see what everyone thought about my son's new gun being 3" low at 25, whether it could have been deliberately sighted in that way (it WAS dead on left/right), or if the scope was way off.
After reading more ballistics charts and playing with the numbers, I have a strong feeling that the scope was off - there was no combination of numbers I could plug in to make it reach zero when it starts off 3" low. This has me a bit worried about the scope, if it can be knocked that far off - hope it's not defective (my brother-in-law bought a gun - we sighted in the way I always do, it was grouping very nicely. He got in the stand and missed 4 shots under 50 yards - never banged it, dropped it, nothing - re-sighted in opening morning !@&$%^#, and he missed another one - found out the crosshairs were loose inside and moved when he slung it).
My other feeling was that the seller just stuck a scope on the gun to make it more attractive to a buyer - he couldn't tell me the last time it was ever shot. Hope this is the case.
brtn610, good point! Again confirming why I typically consider ballistic charts misleading, there's just too many variables.
I'll stand by what I've been trying to communicate this whole time. Want to know where your bullet is going to impact at any given distance? Go shoot at that distance because there's really no way to know otherwise, anything else is just an assumption. Even when I use Strelok Pro and my Kestrel I still go back to the old school ways for confirmation.
I check at all ranges in about 50 yard increments out to my max. range. That range depends on what I'm shooting 30-30 vs 3006. Don't know or care what the 30-30 does at 300 yards but I do need to know what "I" can do at 300 yards with the 06. This is not only from the bench, shoot from other realistic positions and practice. It's not fair to the game if you don't know what you are doing.
Bass, what distance did you zero at? 25 yards? 100 yards? Did you shoot at 150, 200, and 250? Did you record the differences between zeros at the aforementioned distances as well? And did you shoot at those distances using different types and lots of ammo and compare results? Just curious..
I ask because the original post included distances out to 250. I'm not saying your data isn't relevant, but to simply state only an 1/8" difference is a little misleading don't you think? I know you shoot more than the average hunter.
Edit: Pimply, I'm hoping you get the info you're looking for. I just want you to understand where I'm forming my basis. I assume you're using 250 as an actual number that you'd be willing to take a shot at game. If so, you certainly need to shoot your rifle and loading of choice at those distances to verify actual points of impact and not rely on a ballistic chart.
First and foremost , pick a distance to zero your firearm and stick with it. Know what YOUR gun does and eliminate as many variables as you can or are willing to. Shooting is all about consistency. There are too many factors that go into ballistics for you to chase and play the numbers game using factory loaded ammunition without a chronograph and a spreadsheet full of data. Yes I'm fully aware some "charts" will put you in the ballpark, but that's just it you're in the "ballpark." Unless your shooting the same ammunition using the same barrel length (velocity) at the same temperature and elevation as said ballistic chart you need to do your own research.
Second, once you have settled on the ammunition you want to use make sure it's all from the same LOT. Yes, lot numbers make a difference in factory ammo, you can find the lot number on the side of the box.
Third, if you zero at 25 and want to know where the point of impact is at 50 yards shoot at 50 yards and record your data. Then shoot at 100, 150, 200, 250 and so on till you get to the distance you consider your maximum engagement. I don't care how many rounds someone has put down range they can't tell you what your gun is going to do with this ammo at that distance. You need to do the leg work yourself and find out where your point of impact is versus your point of aim at any given distance. That is what is referred to as DOPE in the shooting community.
I've always zeroed my guns at 25 yards, mostly because of available space to do it in my back yard, I can get on paper much faster if the scope/rifle is new and way off, and eliminates the need for a spotting scope or running downrange and back. It's worked for 40 years now.
I played with a ballistics chart and the trajectory for the .243 using a 100 grain round is different if you sight in at 25 vs 100. 100yards gives you a flat trajectory out to about 180 then starts dropping fast, with zeroes at 40 and 100, but then you need 100 yards to sight it in. Sighting in at 25 puts your zeroes at 25 and 250, then drops.
I was just curious if anyone knew the math to figure out what the zero would be if the gun was 3" low at 25 yards.
Wow , I never sighted for both the rise and fall of a bullet . Best would be to get to a 100 yard range . A 25 yard shot does happen , but I'd rather know where it is at a distance . Personally I sight my .308 at 2 inches high at 100 . Then it about dead on at 200 .
