Okay so I am new at this. I've never dialed in for drop compensation before. I set up my new rig in a 7 wsm with a mark 4 scope with M1 turrets. They are 1/4 MOA adjustments. I'm shooting 168gr berger VLDs at an average of 2950fps. I'm using a 100 yard zero. This morning I went on to huskemaws BC Calculator and punched my info in. It told me at 300 to give her 13.2 clicks of 1/4 Minute value. So this is 3.25 MOA. I dial that in. No where close. Once I dialed it all in from there I ended up cranking in 4.75 MOA. The only difference from when I zeroed was that I was now shooting off of a bipod on the ground. What's up?
Scope adjustments
- Thread starter matthewpauls
- Start date
- Location
- Somewhere on the Hudson Bay Coast
The first question that comes to mind is whether your velocity is measured or estimated, that could account for some difference between the computer projected drop and what you observe on the range. Did you enter the correct sight height above the bore? Are your sure you are getting true quarter minute adjustments from your scope? VLDs are more difficult to stabilize than conventional match bullets, and if your bullet is in yaw (slightly) during the time of flight, more bullet surface is exposed to air friction than if the bullet flies point on, so the BC is actually reduced (slightly). Very often, there is a difference between POI between a rifle fired from the bench and one fired from field positions. Use the computer calculations as a guideline, but what is important to you is how your loads and your rifle perform in the field or on the range. Provided you are happy with the level or accuracy your loads produce, keep good records and over time create your own drop tables pertinent to your load for that rifle, record them on an index card, and tape the index card to your rifle stock.
Boomer and Ont have great points. Ultimately, a ballistics program is only as accurate as the data you enter into it. One of the big culprits is the accuracy of ballistic coefficients, and whether you use G1 or G7 numbers.
Having said that, without knowing your altitude or other atmospherics, Exbal gave a come-up of 4.5 MOA from 100 - 300 yards. ...and yes, that sounds right to me.
Having said that, without knowing your altitude or other atmospherics, Exbal gave a come-up of 4.5 MOA from 100 - 300 yards. ...and yes, that sounds right to me.
Get yourself a rectangular piece of cardboard about a foot wide and three feet long, and a thick tip black magic marker.
Using a straight edge draw a line down the middle with roughly six inches on either side of the line, then draw a cross hair line across the bottom that bisects the vertical line.
Use a plumb line and hang this at 100 Yards so it's perfectly vertical and the crosshair line is at the bottom. Set your scope for 100 yard zero and shoot a group at the crosshair. Assuming you've hit near the crosshair line, then set your elevation for 200,300,400 yards and shoot a group. This is a great way to see if a minute adjustment on your scope really results in a minute difference in POI.
As you increase the elevation subsequent groups should stay on the vertical line. If they don't; the target line is not plumb, you're canting the rifle when you shoot, the scope reticle is not level to the receiver, or some combination of the above.
Be prepared to find that you're dialing in the correct elevation change but in the WRONG DIRECTION (I've done it!)
It's not clear if your velocity is estimated or measured but the numbers you're using seem reasonable.
168 gr., .617 B.C. www.hornady.com
Range (yards) Muzzle 50 100 200 300 400 500
Velocity (fps) 2950 2875 2802 2658 2519 2385 2254
Energy (ft.-lb.) 3246 3084 2928 2636 2367 2121 1895
Trajectory (100 yd. zero) -1.5 -0.2 0.0 -2.9 -10.7 -24.0 -43.3
Come Up in MOA -1.5 0.4 0.0 1.4 3.4 5.7 8.3
Using a straight edge draw a line down the middle with roughly six inches on either side of the line, then draw a cross hair line across the bottom that bisects the vertical line.
Use a plumb line and hang this at 100 Yards so it's perfectly vertical and the crosshair line is at the bottom. Set your scope for 100 yard zero and shoot a group at the crosshair. Assuming you've hit near the crosshair line, then set your elevation for 200,300,400 yards and shoot a group. This is a great way to see if a minute adjustment on your scope really results in a minute difference in POI.
As you increase the elevation subsequent groups should stay on the vertical line. If they don't; the target line is not plumb, you're canting the rifle when you shoot, the scope reticle is not level to the receiver, or some combination of the above.
Be prepared to find that you're dialing in the correct elevation change but in the WRONG DIRECTION (I've done it!)
It's not clear if your velocity is estimated or measured but the numbers you're using seem reasonable.
168 gr., .617 B.C. www.hornady.com
Range (yards) Muzzle 50 100 200 300 400 500
Velocity (fps) 2950 2875 2802 2658 2519 2385 2254
Energy (ft.-lb.) 3246 3084 2928 2636 2367 2121 1895
Trajectory (100 yd. zero) -1.5 -0.2 0.0 -2.9 -10.7 -24.0 -43.3
Come Up in MOA -1.5 0.4 0.0 1.4 3.4 5.7 8.3
Like they all said.
many scopes do not move the bullet 1' per 4 clicks. In my experience, very few do. Most of my scopes are more like 6 clicks to the inch. Not a big deal. Shoot at various distances and note the come-ups for your rig.
For a shooting position, rest the back of your hand on the rest, so the hold is "soft" like it will be in the field.
many scopes do not move the bullet 1' per 4 clicks. In my experience, very few do. Most of my scopes are more like 6 clicks to the inch. Not a big deal. Shoot at various distances and note the come-ups for your rig.
For a shooting position, rest the back of your hand on the rest, so the hold is "soft" like it will be in the field.
Thank you Ganderite. I knew that some scopes could be out of the 1/4 minute range but I had no clue as much as 6 clicks to the inch! My velocities were sent through my chrony. Everything went well once I was dialed in, I was just so concerned with that big difference. I know I should only use software as guidelines but it was just so far out to make any sense to me. Thanks guys.
