Posted by on Sep 10, 2025 in Product Review, Rifle Cartridge Reloading

Reloading the .270 WSM with Speer 150-Grain Grand Slam Bullets

This summer one of my main reloading bench projects was to work up a reliable hunting load for the .270 Winchester Short Magnum (WSM) using the Speer 150-grain Grand Slam bullet. My focus was preparing for an upcoming elk hunt, where I wanted a traditional hunting bullet known for deep penetration, reliable expansion, and good weight retention.

Components Used

Why the Speer Grand Slam?

The Speer Grand Slam has long held a reputation as a tough, deep-penetrating big game bullet. While its ballistic coefficient (.383) isn’t as high as modern long-range hunting bullets, the design excels on elk, moose, and large-bodied deer inside ethical hunting ranges. The bonded construction helps the bullet hold together while still creating a large wound channel.

Some handloaders argue the Grand Slam can be harder to fine-tune for accuracy, but I’ve found that proper brass prep, consistent powder charges, and careful seating depth adjustments can make a big difference.

Cartridge Overall Length (COL)

I determined the cartridge overall length using John Nosler’s bullet seating depth method (discussed in an earlier article). From the measured maximum, I reduced the length by .025 inches, which gave me a COL of 2.775 inches.

This approach balances accuracy with reliable chambering and pressure management in the .270 WSM brass cases.

Load Development Results

I tested four different loads using Reloder 19 and Hodgdon H-4350 powders. Both produced solid results, but ultimately, I settled on 55.7 grain charge using Hodgdon H-4350 because it showed excellent consistency and is currently more available than Alliant powders in my area.

The Hornady .270 WSM brass performed very well through multiple reloadings, maintaining uniform neck tension and primer seating, which contributed to the overall accuracy.

POWDERCHARGEFPSSPREAD
R-1958.0280842 fps
R-1959.0288112 fps
H-435055282833 fps
H-435055.7287829 fps

100 yard target .277 Speer 150-gr

Next trip to the range will be for final scope adjustments and with any luck update on terminal performance on a elk, however I must locate this elk later this year.