My method, I know what bullet, primer and brand of brass I will run upfront, and have it on hand when I get a new chamber. Most likely I will know or have researched seat depth before I start.
1. I will load 2 rds at each charge.
A. My formula. For cases that hold under 40gr, do increments of .2gr, 40-50gr capacity, .3gr, and over 50 gr, I will load test rds in .5gr.
2. I will chrono these charges, getting the scope close to zero while doing so. What I am looking for is tighter numbers over a range of charges. I will have a good idea of where these charges will be as far as velocity. I am a believer, you cannot just pick a speed and make it work.
Example:
37.0gr 2875 2899
37.3gr 2890 2910
37.6gr 2901 2920
37.9gr 2939 2941
38.2gr 2952 2955
38.5gr 2967 2975
38.8gr 2989 3010
39.1gr 3015 3030
I am looking for a velocity node, not a flat spot node, most powders I shoot rarely plateau. So in this scenario, I pick 37.9-38.5gr to be my test range. At this point, if I was clueless on seat depth, I would load 40 rds at 38.2(mid) and seat long, take my portable setup to the range and find a suitable seat depth. If known, I would now load 4 rds each from 37.8-38.gr in .2gr increments, so 6 charges, 24rds total. Plus 5 foulers to get on steel at 500. The barrel will get cleaned after this test.
We have a 24"x36" steel plate at 500 yards, this will be my proving grounds. It will look like this, i am going to shoot what I call a modified ladder, basically an OCW and ladder test in one.
View attachment 201470
Now, about 4 rds per charge, the goal is to shoot 2 rds at each dot, looking for vertical dispersion and impacts relative to the dot. If by chance, I have 2 shots really close, the 3rd goes for group, or an extra rd if a shot is biffed and called immediately.
Let's say my target ends up looking like this, which of coarse it wont as I would have group shot on charges 3-5.
But you can clearly see a node from 38.-38.6gr, they held vertical and the impacts are in the same location to the dot, the aim point.
The first 2 charges weren't there, and the final charge we are into a different harmonic zone of the barrel. I could pursue higher if I was not into pressure, but unwise as my barrel still needs to speed up. Right now, I would load charge 38.4 and have some fun shooting, monitoring speeds the whole way till i feel the barrel is broke in, usually anywhere from 40-125 rds, depending on barrel brand. I have had one or two unruly Proof and Bartlein barrels that you never know when they will settle in.
View attachment 201471
After the barrel speeds up, and I feel it is stable, I will evaluate the load to see if it held, if not, I will do a refined process of the original, making sure the load holds vertical at 500, 750, and 1K. Common sense right now says it will take quite a bit more work to get a load to hold waterline at 1K as compared to 500 yards, and we all have different standards.
Shooting an excessive number of groups to prove a load IMO is not needed, every outing whether or not on your mind you evaluate your load. Barrels rarely last over a yr and a half, not wasting barrel life group shooting, if something seems amiss, fix it and move on. I do not shoot paper for score.
Shooting groups or shooting at 100yards to me is a giant waste of time and components unless 100 is your game, have fun. I zero my scopes at 100, that is it.