I have 30-40 manuals. This doesn't include the fliers that powder companies publish. The copyright dates start in 1969 and progress to last year. The manual I feel was the biggest waste of money is the First Edition (Last year) of the Berger Loading Manual. It is computer generated and not confirmed with pressure barrels or firearms. So it is a loose guideline manual at best. I have Lyman Manuals 45th, 46th, & 49th Editions. These are in a series that started in the 1800's by Ideal. In my opinion the measure of a manual is how repeatable are the results not in a laboratory but by the re-loaders themselves. In about 1980 the Ordnance Department of the Columbus, Ohio PD did a series of tests on the Lyman 46th edition and found that, not only on the professional reloading equipment they used, but on the equipment that armatures have available to them from Lyman, Hornady and RCBS. The velocities published were checked in multiple handguns, and found to be the most consistent (Matching published velocity and recommended accuracy) from several manuals (I think 7 current at the time). So on my bench all loads are compared to Lyman #45 and #46. In the 60's, 70's and early 80's the Columbus PD had one of the top pistol teams in the nation. All of the handgun training instructors were NRA Distinguished Marksman, and most competed in multiple disciplines of competition.
I shoot some black powder cartridges and find that for rifles the SPG reloading manual is best not only for load data but also for techniques to assemble accurate and proven longer range rounds.
For 1000 yard shooting, the recommend loads in the Sierra loading manual will be the place to start and tune to your rifle.
The ammo we make cannot exceed the quality of the components we use. Junk brass will not make great ammo. Nor junk bullets; I had a box of 168 grain BTHP Match 30 cal bullets by Hornady (about 1985) that varied in weight by 2.4 grains. However the 75 grain A-Max 22 cal bullets are in the top 2 I use in a 223 Savage at 1000. The loading manuals aren't going to make up for: poor weapons , poor components, or poor loading techniques. Ivan