Nomercy448

I feel like it's trying to tell us something...

Are you asking how to zero your scope, or how to establish DOPE to be used to dial your scope for shots instead of holding over?

I'm a little surprised by either question - you knew to buy a 300RUM, tap over-dia mount screws, install the 20MOA base, understand the difference in first and second focal plane, but then need help either zeroing or establishing a trajectory to let you dial?

Messing with correcting the BDC reticle across various magnifications is a losing proposition. You have to remember irregular subtensions and then work with scaling factors... For hunting, this just doesn't work - too many moving parts. At the range, the time is there, but it's still a massive pain in the @ss. You CAN look up the subtensions at the reference magnification (it's not always the maximum), then scale them based on your magnification settings, but it's really a fool's errand. You MUST do an actual scaling measurement of your scope, because not all scopes are TRUE to their magnification settings - in other words, 5x vs. 25x might not actually be 5.0 times zoomed, which means you cannot simply take the target size read at one magnification and multiply or divide to get to the other... You MUST know the actual relative magnifications for your zoom settings.

The Minox z5 5-25x uses 15x as the reference magnification, NOT maximum magnification. The subtensions for the reticle are found in the owner's manual, available online.

You WILL be better off to completely give up on the BDC reticle and simply dial... So... To get your trajectory...

Go shoot across a chronograph, get a proper velocity for your load and rifle. Look up the BC for your bullet, and google trued values for the BC to be sure you have good info. Download the Advanced Ballistics App, enter accurate environmental data, enter your load and rifle info... It'll kick out a base trajectory.

Shoot at various known distances, dialing the prescribed drops, and record your actual drops. You can input these as truing values to the calculator, which will adjust your muzzle velocity. When you change environmental conditions, you change it in the app, and it'll kick out new corrections.

You can't get away with taping a range card to your stock without understanding how environmental conditions change the outcome. A headwind vs. a tail wind can mean a difference in your elevation dial. A strong side wind can also mean a difference in your elevation - let alone your wind drift. Temperature changes can speed up or slow down your muzzle velocity, and can change your density altitude enough to also make a difference in your elevation corrections. I shot a match yesterday, we started shooting at 24degrees and ended at 55 degrees, and we went from shooting into a 13-20mph headwind to only 1-3mph. The data I used in the morning was a half mil lower (~1.5moa) at 600yrds than the data I used midday. Shooting at 8" targets, I would have completely missed the target if I had not corrected for the temperature change.

Get a data book and the AB app (or strelok), and get familiar with your rifle's trajectory, and how it responds at different temperatures and in different winds.