As mentioned above, you can get a good theoretical start with JBM Ballistics online for free:
https://jbmballistics.com/ballistics/calculators/calculators.shtml
I use the "Trajectory" calculator at the top of the list.
You will need your ammo's bullet BC. Some brands provide this on their website, some don't. There is a wide range reported. For example, SK and Lapua cite their BC's for their target ammo as 0.172. CCI Standard Velocity is cited as 0.120. Eley does not seem to provide the BC of their bullets. Don't stress too much about the "accuracy" of the BC number, as you can "true" this later, based on your real world testing. For a brand you can't find, pick a number from what's out there, and then shoot the various distances to observe the drop effects.
You will also need the muzzle velocity. You can generate this yourself with a chronograph which is your best bet, and if you do, be sure to use a large sample size, like 30 rounds or more, and record ambient temperature and let the ammo sit in that air temperature to make sure it has equilibrated. Or you can take the average V0 off the manufacturer's website. The V0 from the websites is an average and varies slightly between lots and within a single lot. I suspect the lab generated V0 is highly influenced by temperature, barrel length and brand, so your average V0 is likely to be different.
Your scope height center above the bore (sight height) is important to input accurately, because this is a sensitive variable in the calculator.
For the rest of JBM's inputs, it should be straight forward, and you can use their defaults for the atmospherics (temperature, pressure, humidity) to get started. Later you can tweak these with your own input data. I suggest you use a zero velocity wind to start with to generate the drop outputs with zero wind. Later you can game the tool to see how the wind affects the numbers.
You can ignore some other inputs like the minimum point blank range, vital zone, and several others because these do not affect your stats for bullet drop.
At the bottom of the inputs settings, you can chose the range increment. For rimfire, a 5m increment really shows the trajectory much better than the manufacturer's websites which tend to use 25m increments. You will also see major trajectory chart differences for what you enter for "zero range". The zero range is a highly sensitive variable for trajectory, so be sure you know what that is for your notes as you test shoot to verify. For shooting matches I zero at 50m for my Range's distance. But for grouse hunting I zero at 30m. The trajectory difference (and therefore crosshair hold) for grouse head and neck shots at a scope zero distance of 30m is significantly different than a 50m zero, so make sure you keep good notes for your verification shooting tests for what your zero distance was.
Your OP mentions Mrad. JBM gives you the choice in the bottom input boxes to generate the outputs in Mrad and cm, or MOA and inches, or any combination.
Play around with it and you will get the hang of it. On my Microsoft computer, I can right mouse click select and and copy the JBM output trajectory table into first a Notepad text file. Then I right mouse click select and can copy the table into Excel and it formats perfectly. For some reason my machine will not let me copy it direct from JBM to Excel, so the Notepad pasting step is a trick to make it work for then pasting into a spreadsheet.
