Forster .280 AI Loading Tips & Tricks

In my last video, I showed the full process of my .280 AI lightweight hunting rifle build from bill of materials to chambering on the Precision Matthews PM-1440HVT-2. I loaded test ammunition with three different bullets, the process and results of which are detailed below!

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About the .280 AI Rifle Build

At the request of Ultimate Reloader viewers, I recently built a .280 AI hunting rifle based around the new Pristine long action and the new WOOX Superleggera hunting stock.

I added a Carbon Six 7mm 1:8 fast twist barrel, Hawkins Precision hunter bottom metal and magazine, Area 419 Hellfire muzzle brake, Bix’n Andy Dakota trigger, and an Element Nexus 4-25x50mm scope.

About the .280 AI Cartridge

.280 Ackley Improved (AI) is a SAAMI-certified cartridge based on the .280 Remington. The .280 Remington is a .30-06 necked down to 7mm with the shoulder pushed forward 0.050” to prevent it from being accidentally chambered in a .270 Winchester. Typical twist rate is 1:10.

The .280 AI is the 280 Remington with the shoulder bumped up to 40 degrees, requiring less trimming. This cartridge has a slightly larger case capacity with a standard .308 case rim and is typically paired with a 1:9 twist barrel.

The .280 AI provides much of the performance of a cartridge like 7mm PRC or 7mm Remington Magnum, but with a standard .308 bolt face. It is also compatible with .30-06 magazines.

Cartridge Comparison

I consulted Hodgdon’s Reloading Data Center to investigate the claim that the .280 AI provides near magnum performance. I looked at both .280 AI and 7mm Rem Magnum data for 175 grain bullets with maximum charges of H1000. .280 AI had a maximum load velocity of 2675 fps; 7mm Rem Mag had a maximum load velocity of 2692 fps. This is less than 20 fps different!

In our tests, we observed an average velocity of 2,784 fps for five shots with 180 grain bullets. This is faster than the Hodgdon data for .280 AI and 7mm Rem Mag with a heavier bullet! This experiment proved that we could eclipse 7mm Rem Mag max load performance with the .280 AI.

Loading

The .280 AI is a specialty cartridge generally accepting bullets weighing between 120 grains and 175 grains. Hodgdon’s Reloading Data Center has extensive data for a variety of powders including H1000, H4350, H4895, Retumbo, and Varget.

You can fire-form .280 Remington brass or purchase factory brass from a company like Peterson Cartridge. It accepts standard large rifle primers with a .308 case rim shellholder/shellplate.

Loading .280 AI took a few special considerations. I primed all cases using the Primal Rights Competition Primer Seater and used the loctite method to determine the cartridge overall length and the base to ogive measurement with the bullet at the lands. I decided to jump the bullet 0.020”.

I used a standard Forster .280 AI resizing die with APW 7mm expander to control neck tension and a Forster neck tension gauge kit to check it.

For seating, I combined the Forster Co-Ax with the Forster Ultra Micrometer Seating Die. Forster’s instructions for this die caution that the seating stem may not exactly fit the profile of the ogive of the bullets chosen.

This may mean re-profiling the seating stem for bullet ogive. An easy way to do this is to put lapping compound on the bullet and spin it in a drill within the stem. I kept getting rings in my bullets so I had to re-profile my seating stem. I used my lathe and some fine sandpaper to do so.

I couldn’t find any specific load data with my 1:8 twist barrel (all was for 1:9), so I started off conservatively, loading 57.0 grains and slowly working up to 60.0 grains of Hodgdon H1000 with Hornady 180 grain ELD-M bullets in Peterson .280 AI Brass.

(60.0 grains is slightly over maximum load. Do NOT try this at home.) Using a 1:8 twist barrel also meant I could stabilize Hornady 190 grain A-Tip bullets. I weighed all charges using a RCBS Chargemaster Link.

Results

60.0 grains of H1000 had the best chronograph results with a 2784.20 fps average velocity, 5.5 fps standard deviation, and 13.2 fps extreme spread. We did observe very slight pressure signs. The factory brass shoulders moved forward approximately 0.007” when fired. I bumped it back 0.003” when I reloaded it.

While the velocity numbers were good, the accuracy suffered with both the Hornady 180 grain ELD-M bullets and 190 grain A-Tip bullets.

I switched to the Berger 180 grain Hybrid Target bullet and my first five shots tore one ragged hole measuring 0.520” at 100 yards. This accuracy did come with a SD of 20.1 fps and an extreme spread of 58.0 fps.

Conclusion

We were able to exceed 7mm Rem Mag maximum performance with the .280 AI and determined that the bullet can make all the difference. Switching dies and loading on the Forster Co-Ax was simple and painless.

The 1:8 twist worked incredibly well and this project has made it clear that a .280 AI is worth considering when rebarreling a .30-06 or similar cartridge.