My 223 rifle, using a 3x9 scope(55 grn bullet), is sighted in @ 100 yds. If I take that same rifle/round and shoot @ a target only 50 yards away, will the bullet strike at a HIGHER point and if so,how much higher? Should I then aim LOWER,if I'm shooting @ a 50 yd target?

Probably higher, yes. I'd guess maybe half in inch, but you'll have to just try it. Normally with centerfires, the bullet is under the line of sight till around 25 yards or so, then over till it drops back down at the zero range.

Ballistics tables in most reloading manuals may help answer this with more precision. If it's not a handload, just pick something else that is close. You'll probably be within a few tenths.

Whether or not you have to hold off, probably depends on how big the target is :D

All of that depends on how high your scope is set off the barrel. Mine shoots a little low at 50 yards with the same bullet weight. I have a 44mm obj. scope almost setting right on the barrel. You will just have to shoot it and see.

All of that depends on how high your scope is set off the barrel. Mine shoots a little low at 50 yards with the same bullet weight. I have a 44mm obj. scope almost setting right on the barrel. You will just have to shoot it and see.


The farther up from the bore line, the lower it will shoot at 50yards. Won't be a whole bunch, a fraction of an inch for most scope mountings.

Hi Unclejerky -

Why not sight it in at 200 yrds? I'm assuming that it's not a non-target style AR-15-type rifle in .223 since you have it scoped. You can reach out a lot farther than 100 yards with a scopes bolt action or target-grade semi-auto rifle and that round.

Zeroed at 200 yards it will be ~1.5" high at 100 yards and depending on the velocity will first cross the line of sight at ~40 yrds. You can download some trajectory freeware and like MikeG said you can also use tables like the ones in Shooter's Bible. Virtually all centerfire rifle tables will have data complied with the zero at 200 yards. My Shooter's Bible lists the Hornady 55gr V-max at 1.4" high at 100 yards and 7.1" low at 300 yards. Federal 55gr Blitzking is 1.4"/0/-6.9". Remington 55gr Accutip is 1.5"/0/-7.1". Winchester 55gr Silvertip is 1.4"/0/-6.8". Sighted in at 100 yards will give you a drop at 300 yards that may be difficult to visually/spacially compensate for. The FMJ Boat tails have flatter trajectories but their use depends on what you are shooting at.

Also, since none of our groupings are ever perfect, the very slight difference scope hight makes as a factor in trajectory a moot point. I also have a 44" scope that practically rests on my barrel. It's ~1.7" center to center, which is only .2" more than the standard 1.5". Once you factor in your group variability, wind, target elevation, barometric pressure, etc while trying to predict your shot placement that .2" becomes trivial.

Cheers,

The only way to truly know is to put it on target at the range in question. Bullet styles, altitude, humidity, wind, barrel oscillation, your celestial sign, the moon cycle, your tarot reading, everything can keep your rifle from shooting as the "tables" say they should. Just hitting 1.5-2 inches high at a 100yds DOES NOT truly sight it for 175, 200 or whatever yards. Computers and mathmatical formulas are not what applies the pressure to a rifle trigger.

I agree. None of my rifles shoot as the tables say they will. Best to sight in where you want to, then set a target at 50 yards and see where your rifle hits.

Every one of my loads shoots 1 to 1 1/2" lower at 50 yards. The bullet's still rising...

Good morning Gentlemen -

I concur that at the range or in the field it will be very unlikely to duplicate the table data, since it is usually compiled under highly controlled conditions. And I also concur that the best way to sight in your rifle is to place the target at the zero distance and then zero the groups at that distance.

Tables and trajectory data are quite useful though and provide a comparison tool between different cartridges.

JR1 - I am intrigued by your post. What is your scope height? What loads are you shooting? What is your zero range?

Cheers,

My gu shoots similar to JR1's. I am shooting a 55 grain V-Max with 34grs. of 3031. Mine is zero'ed at 100yds. It shoots 1 to 1 1/2 inches low at 50 yds. I have a Leupold 6-18X40 that is setting just off my heavy target barrel. I have about 3/32ths clearance between the bell and the barrel. Is your shooting different, or is it the data you are reading?? Best to shoot the gun and see where it hits at both ranges. Printed data has never worked for me as far as tragectory is concerned. I just use it to compare one caliber to another. Actual use varies quite a bit.

Morning Gismo!

Thanks for the interesting post - My 7mm Rem Mag was zeroed with the paper at 200 yrds. At 100 yrds the groups place about 1.5" high (depending on the load, give or take) and place about 0.25" high at 50 yards. At 300 yards (the end of the rifle range) the groups have dropped ~6.5". My 50mm bell sits just above my bull barrel as well.

My 243 with a 55gr load behaves similar to this, only with a flatter trajectory. The groups place just above of the line of sight like birds on a wire at 50 yards, about 1.25" high at 100, zeroed at 200 yards, and about 5" low at 300 yards (55gr Nosler Ballistic Tip with 43gr IMR4350 (or Varget)).

What I think the difference is between what we see at 50 yards is a factor of where our bullets are in their respective arcs. If your 55gr bullet is still rising (1-1.5" low) at 50 yards but then zeroed as you mention at 100 yards, it must still be rising and reach its zenith well after 100 yards and then crosses the line of sight again at some distance well beyond 100 yards. I am guessing your 55gr screamer isn't arcing between 50 and 100. That is, I just can't envision it being 1.5" low at 50, crossing the line of sight and reaching it's zenith between 50 and 100, and then falling and crossing the line of sight again at 100 yards. I know that was a 'duh, Alec' statement, I'm just thinking out loud. :)

My 7mm RM loads cross the line of sight first at ~45 yards and then again at 200 yards. From the info you have provided I believe your loads cross the line of sight first at 100 yards and then again at some distance beyond that.

Thanks for the info - I was scratching my head but now I think I understand what the difference is.

Peace,

You'll have to check to see how your scope is set up in terms of hitting high or low at 100yds. I've never know anyone to shoot centerfires at 50 yards for group unless it's with open sights. Best wishes.

Cal - Montreal

The Norma website has a fun application. Its a visual ballistics calculator, play around with it - you'll get the idea.

http://www.norma.cc/htm_files/javapagee.htm

At 50 yards, most big-game scopes are going to have a LOT of parallax. If you don't keep your head exactly centered, you'd be surprised how much your groups can be off one way or the other.

I should note that all my rifles are zeroed at point blank range, so most of them between 200 and 300 yards. The scope seems not to matter. My BLR with a detachable mount shoots pert near the same with scope as without, even tho' I don't shoot IT the same! Mine are all for shooting critters, so I just max the range based on the 4" zone for varmints and 8" zone for deer-sized...