LWW wrote:
Probably so to perform at the maximum. And ... ?
Not sure what you mean by "perform at the maximum," but there are myriad reasons that top competitors have to roll their own rifle ammo.
I'll just talk about my situation; it's very typical of other top competitors but there may be variations.
The match rifle is in fact very much a system and its precision potential is dictated by its weakest component. The major components for precision are: rifle, sighting system, ammunition. When you add in the shooter, you can now talk of accuracy.
A rifle and its components can be very precise yet with the shooter will determine its accuracy. A great shooter with a great rifle system can be very accurate and precise. A great shooter with a run-of-the-mill rifle system can be accurate but not precise. A run-of-the-mill shooter with a great rifle system can be inaccurate but very precise. And you can see what you get with an ordinary shooter and rifle.
So, let us concentrate on the first one: great shooter and great rifle system. You have to match the rifle system to the requirements of the game. In my case, we are talking about punching paper with very small targets at 1000 yards. The first obstacle to success in that endeavor is the distance. You can have the best shooter in the world, with the more precise rifle ever, but if the bullet can't get to 1000 yards, you've got nothing.
Enter ballistics programs in which you input various parameters and they calculate a trajectory. In competition there are rules about the equipment you can use and in my case, the caliber choice is limited to two cartridges: .223 Remington and .308 Winchester. Right away, one can see that neither caliber is suitable for 1000 yards with regular rifles and store bought ammo.
I will deal with .308 Winchester here, but I can do (and have done) the same with .223 Remington.
A wise competitor who knows a thing or three about external ballistics will set up parameters for his load to help guide the process. My first parameter is a minimum of Mach 1.25 at the target in the coldest, driest conditions in which I would ever shoot.
Next up, the bullet se******n. We need to find a bullet that has the BC that will allow it to start off using pressures that are not beyond book max and will reach the target going faster than the velocity we listed above, Mach 1.25. One of the things we can do is to use a longer barrel, which will increase the muzzle velocity of the bullet, using an amount of powder that is still safe.
We cannot modify the dimensions of the case or of the chamber from SAAMI specs. In fact, at big matches, the organizers will check you cases, unfired and fired and your chamber.
There are bulletmakers who produce long range target bullets and they provide the G1 or G7 or both BC values. As a rule the heavier the bullet the higher the BC. On the other hand, the heavier the bullet the slower it starts off. The ballistics programs will help you figure out what is the minimum MV required to achieve at least Mach 1.25 at 1000 yards in the coldest driest conditions. We like BC in bullets and will trade BC for MV for the long range.
Once you compute the required MV, you can then check to see if you can safely achieve that with the help of a long barrel. I'm talking about barrels 30 inches or longer. The powder manufacturers will have information about the internal ballistics using their various powders suitable for that chambering.
By this time, it will be obvious that few store bought ammo will meet these requirements and those that do use the least capable bullet for that task. In other words; you can do much better if you roll your own with a better bullet that is simply not offered in store-bought ammo.
The next problem is tailoring a load to your rifle. This is where you have to do some testing in order to find the accuracy node above your minimum velocity. With any luck, you should find one and perhaps two before you go over max on the powder. You then refine the load by adjusting the seating depth of the bullet, again, something you simply can't do with store bough bullets.
When you have THE load, you then have to replicate thousands of times; enter spendy tools like digital scales, power trimmers, annealers, competition grade dies and so on. And you need to use quality components such as brass, smokeless powder, primers and the bullet we talked about earlier. The brass will need attention to make it uniform, as will the bullets. For the powder you buy in big lots and you refine the load for that lot and then load the powder very precisely. I currently load at +/1 .02 grains or one kernel of powder. For the primers, it's lot size purchases of quality match primers and you inspect each and every one.
Finally you assemble all these components in your loading room, making sure that you ammo concentricity is less than .002; I like .000.
When I load a cartridge of my world class ammo in my rifle, I know that wh**ever occurs on the target, the ammo is at the best it can be. I don't question it.
That's why I load my own.