Home Forums Hunting & Shooting Long Range Hunting Need help with long range drop problem!!

Hello Long range shooting enthusiasts,

I have a slight problem that must be corrected! Let's start with the firearm. The firearm is a Remington 700 VLS chambered in .223 Remington outfitted with a Bushnell Elite 6500 4.5-30x50 rifle scope that is bone stock except for a small trigger job. The load I am shooting is composed of Winchester brass, CCI non-magnum primers, Hodgdon Benchmark Powder, and a Hornady 50 grain V-max, nonetheless the load shoots like a house of fire in my rifle, the precision is almost always 1/4 - 1/2 MOA for 5 shots 100 yards. The scope tracks absolutely on rails with no problems at all.

The problem is when I input the exact information into my JBM external ballistics calculator down to the exact muzzle velocity, altitude, humidity, etc. The drop it outputs is too much. So for example I was shooting at a 600 yard jug set out in a field with an angle of elevation so little it can be neglected. I applied the the 13.1 MOA to my rifle scope and sent a round downrange, it hit very high I had to come down. Eventually I "trial and errored" my way down to the proper adjustment where it was dead on the money. It came out to 9.5 MOA of drop instead of the given 13.1 MOA. So the ballistic coefficient for a .224" 50 grain Hornady v-max is .242 G1, when I adjusted my ballistic coefficient in the JBM external ballistics calculator to output 9.5 MOA of drop for 600 yards, I came up with .350 G1. How on earth could there possibly be a 45% error in ballistic coefficient, something is extremely fishy to me

What do you guys think could be the problem? I have a few ideas that are kinda a stretch, but I wanna know what you guys have to say! If you need any more info about the scenario to assist in your diagnosis let me know, I'll get it right to you.

Thanks guys,

Braxton

Please give velocity,alt,humidity,etc, all the info you put into JBM.

I don't know but very fishy. I have two rifles that shoot 600 yds and both don't need more than 6 MOA to do it when zero at 200 yd. Sounds like you will run out of scope real fast if you need to shoot 1500 yds.

Hello Summitsitter,

Way to reply quickly! Anyhow here's all my inputs. Anything I don't list is understood to be unchanged from what JBM had. The target was obviously stationary and there was no wind! Anything I may have missed let me know! Sorry about my inconsistency in my original post saying I had 13.1 MOA of drop, this particular day I had only 12.9 MOA at 600 yards and then the actual drop at 600 yards was only 9.5 MOA Thank you!

Ballistic Coefficient: .242 G1
Bullet Weight: 50.0 grains
Caliber: .224"
Muzzle Velocity: 3400 ft/s
Distance to Chronograph: 0.0 ft
Temperature: 90 degrees fahrenheit
Pressure: 30.02 in. Hg
Humidity: 35%
Altitude: 750 ft

There is your problem if your thinking long range the BC should be .7-.9 or stay out of the long range game.

Don't think you could get the .223 to 1500yds with any accuracy anyways.

Hello 378 Canuck,

If I was zeroed at 200 yards with my rifle and I was using the corrected ballistic coefficient of .350 G1 I would only need 9 MOA to get out to 600 yards. But then you must remember this is only a .223 Remington shooting a 50 grain bullet, I don't need to shoot 1500 yards with this rifle and load, the current rangefinder I have will only laser to 950 on a good reflective target =P Anyhow that's what I have my Remington 700 Sendero SF II chambered in .300 RUM for!

Regards,

Braxton

300 RUM now your talking long range. Stick some of them 225 grain HPBT and your 223 will be back in the closet. LOL

Hello 378 Canuck,

I am a college student with no definite source of income and really can't afford to buy a rifle of caliber that is capable of throwing pills in the G1 ballistic coefficient .7-.9 range like your talking about. Anyhow my Hornady 208 grain A-max's with a B.C. of .648 G1 or more precisely .324 G7 coming out of my .300 RUM at 3000 ft/s is good enough for me when it comes to long range at this time in my life.

Regards,

Braxton

Right on -sounds like a good recipe.

Definitely a good recipe, messed around with RL-25 a bit during load development for the 208 grain a-max, but ended up with Retumbo. The velocities were insane with a stiff charge of Retubmo, 3150 ft/s! I probably could have went to about 3200 ft/s, even though there were absolutely no signs of pressure, but I knew the .300 RUM showed high pressures very well, I knew I was pushing it, although the precision at 3150 ft/s was so-so, so I backed it down to 3000 ft/s and it shoots really nice

Regards,

Braxton

12.9 MOA at 600 yds = roughly 81" of fall at 100yd zero
9.5 MOA at 600 yds = roughly 60" of fall at 100yd zero

That's a pretty big differnce. With your figures you have to be pushing around 3700fps to get it in 9.5 MOA. Few dumb questions here but
1. did you zero the rifle at 100 before stepping out to 600?
2. the scope is in 1/4 MOA clicks, right?

Yeah, something is drastically wrong. Some things to check:

Double check the velocity with a different chronograph. Did you originally clock the load in the winter? It's probably much faster now.


Double check your zero. Maybe you used a different rest or hold on the rifle or the scope got bumped or for some other reason your zero is way off.

How was the range determined? If with a LRF, a jug is a small target for many at that range--are you sure you weren't ranging a bush 50yds behind the jug or something of that nature?

Measure the click value of your scope. You don't really know how much you're dialing until you measure.

Make sure you're using the correct sight height in the program. Makes a little bit of a difference.

Some of the Hornadies are a bit underrated for BC, but not by that much.

Looking at a previous target at 100 yards, I came down 5 MOA and the two 3 shot groups measured 6.25" apart instead of the 5.24" for true .25 MOA clicks. Maybe my clicks are not true .25 MOA? Maybe this could be the problem????

Braxton

It definitely could be; from the sound of that may be the likely explanation. Time to take some accurate measurements of the scope click value.

Sniper Just a few things. Yes your scope could be some what off in .025 clicks. What brand is it and what power? Also an easy way to check is to use a target with multiple bullseye targets. Zero your group on the center target. Then click the said MOA to get it say up and over to the high right bullseye. This helps see how well your scope tracks. A few other things is have you measured your line of sight from center of scope to center of bore? BC can also vastly change with changes in FPS and line of sight. Good luck

Keep in mind for the most accurate measurements, you want to measure over a large distance--30+ MOA will really help.