I am wanting to take out as much of the human element as I can while testing loads.
Then frugality will certainly not help in your search for the best loads and eliminating the 'human element'. There are limits as to how much error you can remove with less expensive solutions. But, you may not actually require the best solutions since you might be satisfied with lesser achievements.
When we attempt to shoot zeros on paper, we usually find that only the best will succeed. When folks are satisfied with 1" down to maybe 1/2", affording the best will not be necessary. However, it's the
repeatability which drives us to spend more money than would otherwise be necessary. Your 1" to 1/2" group should be repeatable, not a once in while occurrence.
Your bags will probably be nearly as good as the Caldwell except for that repeatability. The real test is how you maintain your accuracy tests in the field and what you use there.
For hunting rifles I have used small backpacks, sand bags or sand socks, bipods and tripods. This is after I've wrung out the rifle for load development. For me it always depends on the terrain. If I'm unfamiliar with the terrain or can't scout it, I try to use a bipod and a sand bag for flexibility.
Decide what your parameters are then write out a list of potential solutions.
Enjoy!
