Developing a load to match your rifle is one of the most fun and rewarding things you can do as a handloader. Experimenting with and tweaking different variables such as bullet, powder, and Cartridge Overall Length gives you the ability to find the very best performing load for your rifle. The keys to proper load development are working with reliable data and only changing one variable at a time. Starting with recommended data that has been proven to work by load developers, you can then begin adjusting the variables slightly to dial in your rifle’s perfect load.
To develop a load, you will first have to start within a chosen set of parameters. A good reloading manual will include data for a variety of powders as well as recommendations on Cartridge Overall Length. The easiest way to pick a load to begin with is to first pick a bullet that you think you want to shoot. Depending on the intended use of your rifle, you will probably have a bullet in mind that you want to try. Once you have chosen a bullet, consult the bullet manufacturer’s load data for which powders work best with that bullet. It may be as simple as trying a powder you already have, or you may choose to try out a new powder as well. It doesn't really matter how you pick, just choose one listed in the manual to begin with. If you don't get the desired results, you can always try another powder later. Usually, load manuals will note which powder produced the most accurate results with a particular bullet during testing. While that powder may not be the best performer in your rifle, it is a good place to start. If high velocity and energy are what you are after, you may choose to load the powder that produced the highest velocities during testing. There is no way to guess what combination will work best, but trying one that worked well in testing may help speed up the process.
When experimenting with a powder, it will be necessary to find what weight powder charge performs best with a particular bullet. You can find this by loading a series of rounds with various weights of powder. Be sure to work within the safe minimum and maximum powder charges listed in your manual. Starting with the minimum load, load three rounds with each powder weight working upwards in half grain increments. When doing this, be sure to load all of the rounds exactly the same except for the charge weight. If you change more than one variable at a time, you won't be able to identify which variable changed your results. At this point, pick an arbitrary overall length, using the overall length listed with the load in your manual is a good place to start, or if you know your rifle’s seating depth, you can pick a length that has worked well in the past. Shoot a separate group with each load to find out what charge weight shoots the most accurately. As you progress through the weights, you should see your groups shrink down and then open back up again. As you work your way up, be on the lookout for signs of excess pressure. If you begin to experience heavier recoil, difficult bolt lift, sticky extraction, flattened primers, or other signs of excess pressure, discontinue firing these rounds immediately as you have reached your pressure limit. Note which charge weight produced the excess pressure, then back off any future loads accordingly. It is likely that accuracy will begin to diminish before you reach excessive pressures. Whichever charge weight gives the smallest groups is the one you should use for that bullet and powder combination in your rifle.
It is important to realize that a powder charge that is safe with one bullet may not be safe with another. A bullet’s bearing surface and weight affect the amount of pressure a given load will generate. As bullet weight and/or bearing surface increase, pressure will increase as well. Look in a loading manual and notice that in a given cartridge, as the bullet weight increases, the maximum charge weights decrease. This is due to the fact that the bullet has a greater resistance to travelling down the barrel, and therefore generates more pressure. When testing out different bullets, only use data that was created for the specific bullet that you will be using. Just because two bullets are the same weight doesn't mean they have the same amount of bearing surface, so don’t use load data interchangeably.
Cartridge Overall Length
Once you have settled on a bullet and powder, you will need to choose an overall length to work with. If you know your rifle’s seating depth, you can use that to help you choose an overall length. Most bullets will have a performance “window” of how much distance from the lands they shoot best with. Either by consulting the bullet manufacturer’s data, or by researching on the internet, you should be able to find out what distance to the lands a certain bullet usually prefers. These guidelines are of course just recommendations, and what works best in your rifle may be completely different from what works in someone else’s. A big part of the fun of reloading is getting to experiment, so be prepared to test out a range of seating depths to discover which works best with a particular bullet in your rifle.
When working with Cartridge Overall Length, it is important to remember that every rifle is unique. A load that performs well in one rifle may be abysmal in another. Or, it may perform perfectly well in both. The only way to find out is to experiment. When reloaders talk about adjusting Cartridge Overall Length, they are really talking about controlling how far the bullet has to travel before it engages the lands of the rifling in the barrel. The way to adjust this distance through handloading is to adjust your bullet seating depth. Factory ammunition is loaded to a standard, SAAMI specified, Cartridge Overall Length so that the ammunition will reliably function in all firearms and action types. This specified O.A.L. has nothing to do with optimizing accuracy, and is typically much shorter than the O.A.L. used by handloaders for the same cartridge. For the last several decades, the general rule of thumb was the closer you seated the bullet to the lands, the better the accuracy. Currently, it is understood that this isn't always true. It is true that some bullets and some rifles perform best when bullets are seated out long enough to touch the lands, but other bullets perform best when they have a certain amount of “jump” to the lands. The only rule is: there is no rule.
The best way to find which OAL works best with a particular bullet in your rifle is to load and shoot what is called a “ladder.” To load a ladder, first settle on a powder and bullet combination which already provides a high level of accuracy. Next, decide upon a series of different lengths that you want to experiment with. An easy way to start is to begin loading cartridges to your rifle’s seating depth and then load your cartridges progressively shorter in increments of a few thousandths. Load three cartridges at each length. Be sure to load each cartridge exactly the same except for length. When you are testing and developing loads, you must only change one variable at a time. Now, go to the range and shoot a three shot group with the cartridges of each different length. Whichever length produces the smallest group is the length to use for that bullet in your rifle.
A rifle’s “seating depth” is the overall length of a cartridge that places the bullet in contact with the lands. It is unlikely that you will want to load your cartridges to this length, but you need to know it so that you can gauge how far off the lands you are loading your bullets. Often, you will hear reloaders talk about loading bullets a particular distance off of the lands expressed in thousandths of an inch. Knowing your rifle’s seating depth will allow you to experiment with various seating depths while looking for the most accurate-shooting overall cartridge length.
There are several ways to measure the seating depth of your rifle. The most accurate way is through the use of a specialized seating depth tool. Another way to measure seating depth only requires a fired case, a bullet, a marker, and a set of calipers. The ogive or curved part of the bullet is the part that first makes contact with the lands, so measuring with a bullet and fired case will only give you a measurement that is useful for bullets of the same shape. Different bullets and bullets of different weights will have different ogive shapes, so keep this in mind when measuring and using your seating depth. If you change bullets, you will need to re-measure your seating depth with the new bullet.
Starting with a fired case, insert a bullet into the neck with your fingers. The bullet should freely slide into the case with little to no resistance. Next, lightly press the neck of the case against a hard surface to slightly dent the case mouth enough that it will grasp the bullet. Now, color the entire shank of the bullet with a black felt-tip marker. Insert the base of the bullet into the case just enough that it is held by neck tension. Now, carefully insert the round into the camber of your rifle and close the bolt, but do not pull the trigger. As you close the bolt, the bullet will contact the lands and be pushed back into the case. Open the bolt and carefully withdraw the case and bullet. The bullet may still be in the case, or it may be stuck in the barrel. If it is still in the barrel, remove it by either tapping the butt of the rifle against the bench or the ground, or push the bullet gently out with a cleaning rod. The ink on the bullet will be scraped off to the point at which the bullet wasn't pushed into the case any further. Re-insert the bullet in the case up to the point where the ink was scraped off and measure the cartridge overall length with your calipers. This is your rifle’s seating depth with that particular bullet. Repeat the procedure several times to get a more accurate average. Now, when you want to load bullets a certain distance off of the lands, simply subtract the desired amount of “jump” from the seating depth to get the desired overall length. For example: Rifle’s Seating depth = 3.430 Desired “jump” to lands= .015 Load cartridges to an OAL of 3.415
Once you have found one load that works really well in your rifle, you may wish to experiment with different bullets or powders. Reloaders are typically tinkerers by nature, so it is always fun to try out new or different components. As long as you work within safe limits, with published data, and only change one variable at a time, there is almost no end to the number of different load combinations you can come up with.