Initial Load Development: 300 Winchester Magnum Project

Initial load development for a long range precision rifle can take shape in a variety of ways.

They all involve the mixing of components until you find a combination that works. Powders, primers, bullets, and brass can all be interchanged to varying degrees. The final result of initial load development might not be the exact recipe you end up using, but it should show you where to focus your time and effort. Think of it as the rough draft of a story. It will most likely need some editing, but the basic structure is there. Over the last several weeks, I’ve come up with an outline of how the final load for the 300 Winchester Magnum Project might look. It will definitely need some tuning, though. Here are some of the key points to my process and what I’m learning about this rifle.

Before I started initial load development, I did a lot of research on what combination of components worked for other shooters.

There’s a lot of information available about loading for the 300 Winchester Magnum. It’s a popular cartridge that’s been around for over 50 years. Internet forums, reloading manuals, and articles like this are all sources to consider. Don’t discount word of mouth, either. Some of my best loads over the years were from friends who gave me the exact recipe to use. However, barrels and reamers have different tolerances, measurements can be sloppy, and component lots can change. I used information from all of these sources to formulate a plan for my initial load development. Of course, I adhered to my Five Simple Rules for reloading precision ammo.

The components I used for the initial load development of the 300 Winchester Magnum are readily available in the quantities I need.

I shoot a lot. I refuse to go down the rabbit hole of using components that are hard to find. Once I identify a piece of the puzzle that works well, I want to be sure I can get enough of it to keep shooting at the volume I like. To that end, I started with H1000 powder and CCI 250 primers. Both of these components are available locally, as well as online in bulk quantities. Hodgdon’s Extreme Powders also have the benefit of not being sensitive to temperature swings. From past experience, this combination of powder and primer produces good accuracy, stable velocity, and low velocity extreme spread. So far, it’s producing those same results in the 300 WM.

I recommend buying these components in lots big enough to wear out a barrel. The mixture might not change much from lot to lot, but it’s a variable worth eliminating. I’ve tried mixing powder from different lots with poor results. For reference, one pound of powder equals 7000 grains. If you can’t find components locally, I’ve had good luck with Powder Valley and Midsouth Shooter’s Supply.

Commonly available components.

RCBS Bench Primer w/ CCI 250s 

Realistic accuracy goals were set for this project and I didn’t get hung up on using any one particular bullet.

My threshold for precision from my long range hunting rifles is .5 MOA. Much more than that, and my confidence in taking the long shots goes down. Before I pursue a load any further, I like to see some groups in the .5 to .75 MOA range. I don’t think you can tune a 1 MOA load very easily, if at all.

As long range hunters, we have a very good selection of projectiles to choose from. From my experience, as long as the bullet is placed in the right spot, match-style bullets work very well at killing animals quickly. Here is a good example. I don’t need or want a bullet that has controlled expansion or a bonded core for this kind of work. I want the bullet to land in the vitals and cause massive bleeding. The more sharp edges, the better. I’ve had great success with Berger, Hornady, and Sierra match bullets in multiple calibers.

A good barrel should have no trouble spitting out sub-MOA groups with any one of those bullets during initial load development. These are the bullets I’ve tried so far in the 300WM:

• Berger 230 grain OTM Tactical. For its weight, the 230 OTM Tactical has a relatively short nose section. I was able to load this bullet at magazine length and still contact the rifling in the barrel. An easy way to measure nose length is to measure the overall length of the bullet, then measure from the base to the ogive with a comparator. The difference is the nose length. Or you can check out bullet specs in Bryan Litz’s book, Ballistic Performance of Rifle Bullets. That book is handy if you want to compare bullets without having to buy them.

The 230 OTMs shot very well in the 300 WM. All groups were in the .50 to .75 MOA range, reaching 2800 fps muzzle velocity with no pressure signs.

• Berger 215 grain Hybrid Target. This bullet has the longest nose of any .30 caliber bullet I could find; .905” from ogive to meplat. With my magazine restriction and chamber, the 215 Hybrid was jumping pretty far to the lands. It still shot into the .60-.75 range, so it’s worth another try. Maybe it will shoot better, further away from the lands than I tried.

I was able to break 2900 fps without pressure with the 215 Hybrid.

• Hornady 200 grain ELD-X. This one was a disappointment. Introduced by Hornady last year as an “ALL-RANGE hunting bullet”, the ELD-X was on my list of bullets to test this year. Unfortunately, it shot terribly in this barrel. I tried several velocity nodes and a wide range of seating depths. It never produced a group smaller than 1.5 MOA for me. That’s not to say it’s a bad bullet, it just didn’t shoot well in this barrel. It’s off the list for now.
• Hornady 208 grain AMAX. This is the bullet that Hornady is supposed to be improving on with the ELD line. My experience with the AMAX in other calibers has been extremely positive. This barrel shot the 208s effortlessly into .50 MOA groups with several charges. This bullet is jumping .040” to the lands at magazine length.

The 208 AMAX reached 2900 fps without pressure signs.

From left to right: Berger 215 Hybrid and 230 OTM Tactical, Hornady 200 ELD-X and 208 AMAX.

Initial load development was done methodically, with careful notes kept of every detail.

This is a point worth stressing at every opportunity. Keeping good notes of your loading process is critical to safe, efficient reloading. As noted in the New Brass Prep article, I already had a foundation of data on my brass. Now I know how much the case stretched from firing, and how much I need to push it back during the next sizing cycle.

I keep notes in my loading journal and on targets, of as many details as possible, including:

• Seating depth in relation to the lands and magazine restrictions.
• Powder charge.
• Component lot numbers.
• Group size and velocity, along with environmental conditions while testing.
• Tools used for loading and measuring. For instance, if I have multiple comparator inserts for a caliber, which one did I use? They can vary in dimension.
• Point of impact change with various loads. This barrel is very stable, with all groups impacting within one inch of each other.
• Tempo of fire during the testing.
• Any changes in neck tension during the process. I changed from a .334 bushing to a .333 bushing to see if it affected the ELD-X load. It didn’t affect any of them.
• Every point of measurement on the brass. That includes neck O.D., head to datum length, web O.D., and overall length.
• Any unusual things that occur with the rifle or scope during the testing, like a sudden shift in zero or mechanical issues.

As I begin round two, I’m gaining confidence in finding a quality long range hunting load for the 300 WM. I’ll be using brass that fits the chamber now, and I’ve eliminated some variables in components. I know I’ll be using a charge of H1000 between 75.0 and 78.0, depending on which bullet I choose.

Because I do all of my load testing from the same position I primarily hunt from, my form and trigger press are getting honed as well. I also have a pretty good zero on that Nightforce ATACR now. I sense good things are to come from this rifle.