.26 Macho Cartridge — Wildcat Notes

The genesis of the .26 Macho came during a benchrest match in May 2014. Fellow competitor Steve Grosvenor brought up the idea to build a custom cartridge. I thought the idea was interesting, so together we started planning. The goal was simply to develop an accurate hunting cartridge that would be devastating on deer-size game. We decided to explore the .264/6.5mm caliber, which is known for its inherent accuracy and healthy bullet selection.

Steve did a lot of research and decided on the .260 Rem. as the parent case. The .260 has shown it will digest a lot of different powders has decent velocity and low recoil.

Most .26 caliber bullets are long, slender, boattails, but I wanted a shorter, flat-base bullet that would not have to be seated deeply in the case. We also wanted a bullet heavy enough for deer-size game but light enough to get some decent velocity. We settled on the Sierra 120-grain Pro Hunter bullet.

We did not want to turn our case necks, so we decided on a .297-inch neck, which would give our loaded case necks slightly over .002-inch clearance over the heel of the bullet.

We wanted the proven accuracy and reliable feeding of a 30-degree shoulder angle, along with more case capacity than the .260 Ackley Improved provides. We ultimately decided upon pushing the shoulder forward roughly .080 inch to accomplish this. The .26 Macho ended up with 56.4 grains of water capacity—a significant increase over the .260 Rem.’s 52.8 grains.

We sent our reamer dimensions to Dave Kiff at Pacific Tool and Gauge. Kiff gave us a few recommendations, and we received the finished chamber reamer in early 2015. The project also required custom dies, and I sent three fired cases and a copy of the reamer print to Hornady’s Custom Shop. A few weeks later, two perfectly made dies arrived in the mail.

To fire-form the brass, I took Lapua .260 Rem. brass, loaded it with a stout load of H4350, used a lot of neck tension and seated the bullet long to engage in the rifling. It took two firings to really sharpen things up.

For load work-up, I started with H4350 because it is a proven powder in both the .260 Rem. and .260 Ackley. I knew I would be safe by starting with a low powder charge at 41 grains, and I worked my way up by shooting a ladder-load test at 200 yards. (Editor’s note: To learn more about this, visit our website and search for “ladder test.”)

The sweet spot ended up being around 48.5 grains of H4350. I started shooting groups with powder charges in that range. The proven winner with H4350 was 48.7 grains, with multiple groups at 100 yards under half an inch.

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I then experimented with different powders, neck bushings, and seating depths to see if I could find a better load. I tried Reloder 15, Reloder 16, Reloder 17 and H4831 SC. All produced sub-one-inch groups at 100 yards, which tells me the Macho is a good eater just like its parent case. The 48.7-grain charge of H4350 (.293 bushing, CCI BR2 primer) became my go-to load. It pushes the 120-grain Sierra from a 26-inch barrel just shy of 3,200 fps—a pretty good boost over the 2,900 fps the .260 Rem. does with the same-weight bullet.

After three successful seasons and three different bucks, it is rewarding to report that we met our goal. The .26 Macho can accurately propel the 120-grain Sierra bullet to speeds great enough to allow the bullet to create a devastating wound channel on deer-size game.