New Rifle: Phoenix Weaponry’s 45-70 Auto AR

New Rifle: Phoenix Weaponry’s 45-70 Auto AR

Shooting a modified version of the powerful and classic straight-walled cartridge, Phoenix Weaponry's 45-70 Auto Christine rifle can tangle with nearly any game on earth.

How did Phoenix Weaponry take the .45-70 Government and make it the semi-auto-compatible 45-70 Auto?

  • Phoenix rebated the .45-70 Government's rim to make it function in the rifle.
  • The modification allowed the use of standard .308 AR-10 parts.
  • The rifle boasts a Douglas barrel with a 1:14 twist rate, perfect for heavier bullets.
  • The 45-70 Auto Christine has Phoenix's custom trigger, set to 3 pounds.
  • Cost is prohibitive for many shooters, with a price of $4,800.

The .45-70 Government conjures up thoughts of a bygone era of boundless buffalo herds and the equally limitless American frontier. And, against odds, the powerful straight-walled cartridge continues to elude becoming a footnote in history books as some novel relic of yesteryear. It is still alive and well today, a favorite of shooters who prefer slower, heavier rounds that can handle nearly anything that treads upon hoof, paw or foot.

Photo: Phoenix Weaponry

There are plenty of modern-day rifles chambered for the .45-70, from classically inspired single shots to the most up-to-date lever actions. But if Phoenix Weaponry has its way, shooters will look at the more than century-old cartridge in an entirely different light from here on out. That’s because the Colorado-based AR manufacturer has its sights set on reinventing the large-bore round as fodder for a semi-automatic rifle.

In one of the more unique moves in the AR market in recent years, Phoenix Weaponry has introduced an AR-10-style rifle chambered for the classic round (or at least a version of it) — the 45-70 Auto. Also lovingly known as Christine, the rifle represents perhaps one of the greatest leaps for the cartridge since it transitioned to smokeless powder. Although, getting the good old Government up to speed for a modern rifle platform did take some doing — not to mention a smidgen of ingenuity.

The obvious hurdle to cross was the .45-70’s rimmed case. While not impossible, it would take some intensive re-engineering to modify an existing semi-automatic to reliably chew through this style of cartridge — from bolt to magazine and what have you. Phoenix opted for the easier option, and instead of tinkering the rifle around the cartridge, it re-designed the brass to the gun.

What they came up with is elegant in its simplicity. The company merely rebated the rim, essentially making the cartridge rimless, thus highly compatible with the AR-10 platform. The results were right on the money, with the modified .45-70 cartridge so in tune to the rifle Phoenix was able to utilize it’s everyday .308 Win. bolt head, carrier and receivers.

45-70 auto -second
Photo: Phoenix Weaponry

And the company didn’t have to sacrifice any of the cartridge’s performance shoehorning it into an AR-10. Phoenix claims the rebated case is reloadable with existing .45-70 data — based on Ruger No. 1 loads — and standard dies. The only thing that changes in the process is the shell holder. One compatible with a .308 is required.

Ammo, as expected in a specialty set up such as the .45-70 Auto, is a concern. Your local shooting supplies store isn’t going to be brimming with .45-70 with rebated rims anytime soon. Phoenix foresaw this issue and includes 50 introductory cases with a new rifle and the option to buy more factory-modified brass straight from the company. But Phoenix hasn’t turned its back on dyed-in-the-wool D.I.Y. folks — at least ones with lathes. Cutters are available from the company. So motivated shooters with access to a machine shop can turn off-the-shelf .45-70 Government brass on their own.

The 45-70 Auto itself appears stoutly built, constructed around Phoenix’s RFL upper and lower receivers, originally designed for the company’s .308 builds. The company turned to Douglas Barrels out of West Virginia for the chrome-moly number on the 45-70 Auto. It is attached with custom bushings, is 18 inches in length and is a custom profile — very much bull. The barrel is button rifled with a 1:14 twist, which is quite fast for the caliber and opens heavier bullet options to shooters. The barrel is topped off with Phoenix’s Chevron muzzle brake, designed to keep the line of sight free and clear shot to shot.

Christine utilizes a rifle-length gas system with a low-profile adjustable gas block. It is outfitted with Phoenix’s 15-inch, free-floating modular aluminum handguard that features in-house manufactured Picatinny rail sections for the quick addition of QD sling mounts, and what have you. And it boasts the company’s custom trigger, tuned to a crisp 3 pounds.

Finally, the 45-70 has a Magpul adjustable ACS stock and MOE pistol grip. And the nearly 10-pound rifle is Cerakoted in Flat Dark Earth and comes with a 10-round Magpul magazine, modified to hold six rounds.

45-70 auto -third
Photo: Phoenix Weaponry

There is a rub to getting a 45-70 Auto in a gun safe, however — price. An AR unique as this doesn’t come cheap; Phoenix has a hefty $4,800 basement on the behemoth and will customize as far as a shooter's wallet can handle. It’s definitely not an ‘Everyman’s’ rifle, nor does it appear Phoenix intended it to be.

Like all special ladies, Christine is one of a kind. She'll most likely attract shooters as unique as her. And they could be well served with the investment. Up to and including dangerous game, there's little on God's green earth she can't handle. 


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  1. Things I don’t understand here

    1. Why not just blow the .308 case out straight? They are made heavy enough for 52,000psi and require no further modification other than trimming to proper headspace. They will also fit 10 rounds in the 10 round magazine and give about the same performance as the wildcat .458-2″ American.

    2. Why the 14″ twist? Most original .45-70’s have 20-22″ twists which was more than adequate for 500grain bullets propelled by black powder at 1200fps. The .458 WinMag was given a 14″ twist. This proved to be a mistake on Winchester’s part. They advertised the cartridge asreaching 2200fps, but in the real world it produced less than 2000fps. A friend had a Model 70 that came from the factory with ugly reamer marks on the top of the lands. It shot ok, but eventually he rebarreled it with a 22″ twist barrel of the same length. Just that change alone gave him the original advertised velocity, the additional 200 fps, and the bullets were more than adequately stabilized.


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