Forster .300 WSM Reloading

Completing a rifle build is only part of the process. Next comes finding what load works best. In this video, I walk through the process I go through to load precision .300 WSM ammunition.

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About the Build

I recently showed my first .300 WSM build ever featuring a Pristine Action, Carbon Six barrel, WOOX Exactus stock, and Bix’n Andy TacSport X trigger from Bullet Central.

This build was inspired by Lapua’s release of .300 WSM cases.

About the Planning Process

I always begin with a printed copy of the SAAMI diagram for the cartridge I am loading for.

The cartridge specifics are critical for reloading while the chamber specifics drive any custom build. One of the first things I consider is cartridge overall length.

Though .300 WSM is a short action .30 caliber cartridge like .308 Winchester, its longer cartridge overall length (2.860”) requires a different magazine.

I also look at case rim diameter. This is important to ensure you have the proper bolt face and shellholders. When it comes to load data, I always reference manufacturer data. Hodgdon’s Online Reloading Data Center is one of my favorites.

Every caliber has a weight range of bullets it can accept. The .300 WSM has a very wide range, from 110 grains to 220 grains. When selecting a bullet, consider your purpose and the twist rate of your barrel. My .300 WSM has a 1:9” twist Carbon Six barrel.

In example, the Hornady .30 Caliber 208 Grain ELD Match specifies a 1:10” twist rate. This is the minimum twist rate required to stabilize the bullet. I tested a variety of bullets while breaking in my .300 WSM custom rifle including Sierra .30 Caliber 155 Grain MatchKings.

At 100 yards, a three-shot group with the 155 grain SMKs measured 0.343”. The following five-shot group grew to 0.660”. This may partially be due to the fact that I’m using a carbon-wrapped barrel without giving it time to cool down.

I fired some more groups with the 155 grain and all came in around 0.6” for five-shots. I tested some other bullets, with Hornady’s 208 Grain ELD Match yielding the best results with a 0.488” five-shot group at 100 yards.

While testing it is important to eliminate as many variables as possible. Check to make sure there is nothing loose on the gun, like a suppressor, that can skew the results!

I follow this process with every gun I load for. I start with a variety of bullets and powders and narrow those down to the ones that provide the performance I am looking for. I look for small groups and a standard deviation around 10 fps. Hornady’s 208 Grain ELD Match with H4350 yielded an average velocity of 2701.4 fps, an SD of 11.3 fps, and a 32.2 fps extreme spread. The Sierra 155 grain SMKs with Ramshot Hunter also had an SD around 10 fps, but larger groups.

About the Components

I entered the project with Lapua .300 WSM brass and through testing landed on Hornady’s 208 Grain ELD-M bullets.

They had the best precision out of the bullets I tested, so I kept with Hodgdon H4350, the powder I used in my test loads. Bullet weight selection is critical. Powder selection is also important, but I did not test very many.

I determined the proper burn rate and looked at what I had available. I paired this with Federal #215 large magnum rifle primers.

About the Equipment

For this project I decided to load on the Forster Co-Ax with large jaws installed. This press has two sets of universal shellholders—one for small primers and one for large primers.

I used the large set for .300 WSM. I decided to use a Forster bushing die for sizing and Forster Ultra Micrometer die for seating. The bushing die requires a calculation to determine which bushing to use.

Bushing Diameter = bullet diameter + 2x brass thickness – 0.01 (for press fit) – 0.01 (for springback)

.308 + 2(0.14) – 0.01 – 0.01 = 0.334” bushing

The above is an approximation as there are a number of variables. If you anneal your brass with a machine like the AMP Mark II DB, you will get hardly any springback.

There is a second way to determine the proper bushing diameter. Take a loaded round and take a micrometer measurement of the neck area.

This is the ending value to work backwards from. This method indicated a 0.337” bushing would be most appropriate. Receiving two different values, I took a look at the physical bushings available: 0.333”, 0.335”, and 0.337”. I decided to start with the largest and see if it would produce sufficient neck tension.

I am priming on the Primal Rights Competition Primer seater with a magnum shellholder and dispensing charges with the RCBS ChargeMaster Link.

Loading precision ammunition takes measurement checks. For this I have the Forster neck tension gauge set and Forster Datum Dial.

Reloading

As always, the first steps are depriming and sizing. I used a decapping die to deprime a piece of brass so that I could get an accurate shoulder bump reading from the datum dial.

Referencing the chart inside the datum dial kit, I used the 0.420” circle to zero the deprimed piece of brass on the calipers.

With this complete, I installed the appropriate bushing in the Forster full-length sizing die and secured it in the Co-Ax with the ring lower on the die. I used a Forster Accu-Ring which features 0.001” increments for easy reference.

I raised the ram and lowered the resizing die until it touched the shellholder as an approximate starting point. Next I lubed the same case I measured, ran it through the sizing die, and measured it on the datum dial to see how much the shoulder bumped.

I made adjustments to the sizing die and continued measuring until I had about 0.02” shoulder bump, then tightened the lock ring to preserve the setting.

Keep in mind that it can take depriming and zeroing more than one case to complete this process. Before priming, I checked neck tension with the appropriate gauge.

I was at minimum neck tension. Greater neck tension is a personal choice. After resizing and priming, it was time to add powder, 61.0 grains of H4350.

To set up the seating die, I started with the die in place but not bottomed out with the ram raised. Remember to ensure the micrometer scale is facing you.

I seated a bullet, removed the datum dial from the calipers and zeroed them, and measured the cartridge overall length. I needed 2.84” and it measured over 3 inches.

I adjusted the die micrometer, reseated the bullet, and measured again, repeating this process until I was within 0.015”. If you want to fine tune bullet jump for your rifle, consider working off the lands.

Conclusion

The final step was testing the ammunition on some steel targets on the ridgeline.

The .300 WSM packs quite a punch in a compact package. Now that you know my loading process, what does yours look like? Is there anything you do the same, differently? Drop a comment and let’s start a discussion.