Ballistic Table Is Not Matching Scope Clicks

[James Remington]

gun)I'm new to LRH, so please be kind. I'm having an issue with my new rifle. It's a budget build. It's a Marlin xs7vh in .308. Scope is a Falcon Menace FFP 4-14x44. The Reticle is in MOA, and the Turrets are 1/4 MOA. I read that the Federal Power Shok 150 grain soft point bullets shoot great through these guns, and I agree. They group very well, but my problem is with the ballistics/turret. I think I correctly filled out the information and printed the ballistic chart off of Federal's website. Even the Hornady Ballistic chart looks the same for the same bullet. Anyway, here's the issue. The gun and ballistic chart are zero'd at 200 yards, and I've calculated (using a calculator) how many clicks to move the turret. For example: (with zero at 200yards) 400 yards is a 25.3 inch drop, and a 6.0 minute of angle drop, which means 24 clicks in my 1/4 moa click scope. However, that's incorrect and it's actually 4 inches low which equals 20 clicks. What have I missed? At 500 yards the clicks are exactly what the ballistic table says it is. 10.1 moa low and 40 clicks puts me dead on at 500 yards. I tried it, but why did I have that issue at 400 yards, and a similar issue at 300 yards?

 

[FearNoWind]

Welcome aboard ...........

The gun and ballistic chart are zero'd at 200 yards, and I've calculated (using a calculator) how many clicks to move the turret. For example: (with zero at 200yards) 400 yards is a 25.3 inch drop, and a 6.0 minute of angle drop, which means 24 clicks in my 1/4 moa click scope. However, that's incorrect and it's actually 4 inches low which equals 20 clicks. What have I missed? At 500 yards the clicks are exactly what the ballistic table says it is. 10.1 moa low and 40 clicks puts me dead on at 500 yards. I tried it, but why did I have that issue at 400 yards, and a similar issue at 300 yards?

"400 yards is a 25.3 inch drop, and a 6.0 minute of angle drop" - it's actually 6.6 MOA (25.3*1.047/4) which would be 26 "clicks".
1 MOA is 1 MOA at 100 yards and 1 MOA at 400 yards or at any other yards. If you want to avoid confusion, get the inches and clicks out of the equation. 20 "clicks" on a MOA turret will equal 5 MOA. If you count "clicks" you'll make a mistake - the click stops are usually soft and difficult to feel so missing one or more can make a big difference. Just read the turret adjustment knobs in MOA.
Try to understand this about scopes and ballistics charts.
Scopes don't always adjust precisely to the specs. in the manual. The manual says 1 click = 1/4 MOA but if you run a verticle test on the scope you may find that it's actually something slightly different and that the difference may not be linear. That is, it may change depending on the distance to target you're dialing in.
Ballistics charts are estimates. They are not precise and they're only as good as the data entered by the user.
As they say, GIGO.
If you select a G1 BC for your calculations when using a scenar bullet you're going to get incorrect output. Use the G7 BC factor whenever you can.
Get your MV information, naked bullet length, bullet weight, caliber, weather data, rate of twist, bullet BC, zero range and sight height and write it down.
Use the ballistics calculator on this site - it's very good.
Use the Miller formula to calculate stability http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi ( Output is red for unstable, yellow for marginal stability and green for stable.)
Take your rifle to a range where you can shoot the longest distance possible, select an aim point and move from 100 yards to 200 yards to 300 yards and further if you can, making adjustments that your ballistics chart has provided.
Always use the same aim point for the entire series of five shot strings and mark every shot with the distance it was fired from. If you have to change targets because the holes are so overlapping that they become confusing you can change targets but make sure they are all the same and the aim point is consistent. Don't do anything different than the ballistics chart says and don't change your aim point at any time.
Take your target home, compare the distance from the center of the group you fired at each yardage with the aim point and correct your ballistics dope sheet with the actual data.
Go back to the range and do it all over again. You should have tightened up your accuracy by a good margin.

 

[Mateo]

X2. Couldn't have said it so perfectly.

 

[James Remington]

lightbulbExcellent information. I ran my information in the G7, and it looks surprisingly closer to what my measurements on the range were. I greatly appreciate you taking the time to explain. I suppose I was hoping for magic to take place when I put in all my variables, and then took it to the range. No such luck. Funny enough, I shot again today, and spent a box of ammo and plenty of cleaning patches trying to figure out why I couldn't keep a group. I looked over my weapon, and come to find out my scope had slid forward nearly 3/4 of an inch. You would think that I would have seen the eye relief difference, but it's simply a new set-up that I'm not used to yet. Budget build meant Burris Tactical rings for me, and I apparently didn't tighten them down enough, nor check them after a few shots. FearNoWind, thank you again for the information, as well as the welcome aboard. This is my first ever time using a forum, and I'm trying to learn and navigate through it.

 

[7magcreedmoor]

One more thing to remember: trajectory validation process. No matter how good (read: expensive) the equipment you use, you must perform trajectory validation to shoot long(er) range well. If using a chronograph to measure muzzle velocity, you must accept that there will be some error. After gathering your initial data and printing out your drop chart, you must go back to the range and test again, shooting at multiple ranges, for example: a 100 or 200 yard zero, then an intermediate distance, say 500 or 600 yards, then the longest distance you would like to hunt at, say 1000 yards. Record the turret settings, and the actual point of impact deviation (there will almost inevitably be some), then go back to your ballistic program and use the validation feature if it has one (like the one on this site) or adjust the MV until you get output that matches your observed data (assuming the BC you have from the manufacturer is reliable- read Bryan Litz for an excellent treatise on this). The final muzzle velocity you get from this process is the truth. Then you can print drops that will work in the field, so long as your environmental variables are accurate. I say this taking on faith you have already tested and quantified the true adjustment interval of your scope as mentioned in a previous reply to your post. That is something you must do before any of what I have said can work. Have fun, it will be great.

 

[James Remington]

@7magcreedmoor. Copy that sir. I understand and receive. I've printed off both replies to my thread, and greatly value the information provided. Long range shooting/hunting fascinates me greatly. It's far more to me than just hearing a ping on some steel at 600 plus yards. I have a Remington Sendero set up with a Swarovski Z6 I, with a TDC reticle, and I'm convinced that it's near the ultimate weapon for sitting in a box stand and harvesting deer. The 180 grain soft points line up closely after using the Swarovski software to find a good zero (of 225 yards). The lines are fast, and that round is deadly on a whitetail. Therefor, know that all the help and information provide by you all will be utilized and much appreciated. Thanks again and happy shooting.