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The Ultimate Reloading Manual
Wolfe Publishing Group
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The Ultimate Reloading Manual
hornady superperformance

A Case for a New Wildcat

Author: Richard Mann / Wolfe Publishing Co.
Date: Nov 05 2008

There is something inherently enjoyable about wildcatting a new cartridge. Some shooters like the idea that they were first to make the conversion, and some like the notion of building a cartridge that fits their specific needs. Others just enjoy having something different – like a custom rifle, custom car or a special ham sandwich on pumpernickel with peanut butter like no one else can make.

At the Remington new products seminar conducted during the middle of October 2008, a new cartridge designed specifically for the AR-15 platform was unveiled. The cartridge is called the .30 Remington AR, which I feel certain gun guys will shorten to .30 RAR. Loaded with a 125-grain Core-Lokt or AccuTip bullet, the cartridge will have an overall length identical to the .223 Remington with a muzzle velocity of 2,800 fps. The idea, of course, is to provide those who like to hunt with AR-style rifles a .30- caliber alternative that’s not as heavy as the AR-10 or R25 which are designed for cartridges based on the .308 Winchester case. It also allows you to get there by just buying a new upper for your current AR-15. (Initially, Remington will only offer complete rifles.)

The .30 Remington AR (center) is shown with a .223 Remington (left)
and a .308 Winchester (right). This is a short, fat case similar
in appearance to a 6mm BR or a 7.62x39mm on steroids.

Citing light weight and low sectional density, a number of gun writers in attendance were skeptical about the ability of the .30 RAR’s 125-grain bullet to kill deer when started at 2,800 fps. This seems odd since energy figures are similar to a 120-grain, +P .257 Roberts load and few will argue its suitability on deer-sized game. Sectional density changes immediately after impact, and it’s the sectional density and weight of the deformed bullet that matters. In the end, the effectiveness of the .30 Remington AR will be determined by the terminal performance of the bullets used.

Switching gears, some thought should be given to the wildcat potential of the .30 RAR case. The .30 RAR has the same rim diameter as the .376 Steyr, but overall case length was reduced to 1.53 inches to permit the cartridge to work in .223 Remington/.450 Bushmaster magazines. AR-15 uppers will, of course, utilize a larger bolt head to work with this cartridge.

I can see some benefits of wildcatting this case. With a powder capacity significantly larger than the 6mm PPC and slightly more than the 6mm BR, a 6mm RAR would offer higher velocities for benchrest shooters who are fond of 6mm cartridges. It could also provide a larger bore, high velocity alternative to the .223 Remington for varmint/ predator shooters who prefer AR-style rifles. A .35 RAR would slightly better standard pressure .35 Remington performance but from an AR platform.

Looking at powder capacity and operating pressure as a means of predicting cartridge performance, we can make a guess at what kind of velocities we might expect from various wildcats based on the .30 RAR case. I found that a 6mm BR case will hold 30 grains of Varget powder. Depending on how the shoulder and neck of a wildcat 6mm RAR were treated, it should hold about 36 grains of Varget. That’s an increase in powder capacity of 20 percent.

Velocity tends to increase at one fourth the rate of powder capacity, so given identical pressures, we could reasonably assume a 6mm RAR would shoot about 5 percent faster than a 6mm BR. SAAMI lists the maximum operating pressure of the 6mm BR at 52,000 psi and Remington says the .30 RAR is loaded to 55,000 psi. For all practical proposes these are the same.

This means that, conservatively speaking, a bolt-action 6mm RAR with a 24-inch barrel should be capable of launching a 55-grain bullet at 3,800 fps, a 70-grain bullet at about 3,400 fps and an 80-grain bullet at around 3,300 fps. According to Hodgdon load data, this performance is similar to a 6mm-250, a .250 Savage case necked down to 6mm, which will hold about the same amount of Varget powder as the .30 RAR case. Of course, a 6mm-250 will not work in a rifle based on the AR-15 platform because of its overall length. Also keep in mind that velocity from a gas-operated AR would be slightly less, at least 150 fps according to Tim Tanker with Remington, than what you could expect from a bolt gun with the same length barrel.

For bolt rifle conversion, the .492 rim diameter is an issue but not insurmountable; opening a bolt face and installing a Sako or M16 style extractor is a common modification. So, I can see a 6mm RAR getting serious attention from benchrest shooters. For AR enthusiasts who purchase a .30 Remington AR, a 6mm RAR would only require a new properly chambered barrel and should make a potent predator rifle.

This schematic shows the dimensions for the new cartridge case from
Remington. Overall cartridge length is intended to be less than the
available space in a standard AR-15 magazine, about 2.26 inches.

For deer and hog hunters, a .35 RAR on an AR platform is at least moderately appealing. A 200-grain Remington Core-Lokt SP or PSP bullet seated so the base of the bullet is even with the bottom of the neck is within the overall length necessary to work in standard AR magazines. Based on the velocities I get from my .35 Remington Super, which holds four more grains of powder than the .30 RAR case and is also loaded to 55,000 psi, a .35 RAR should generate about 2,300 fps. Wouldn’t that make a nifty, close-range whitetail rifle?

So, we shall see what the wildcatting future holds for the .30 Remington AR case. I’ve already talked with Dustin Emholtz at DPMS about building one of his Sportical uppers for a wildcat cartridge based on the .30 RAR. (DPMS worked with Remington on the development of the .30 Remington AR.) Dustin is eager to give it a shot, but I am sure someone with a thicker pocketbook will beat me to it. And, for what it’s worth, Remington is considering this case to be the start of a whole new family of cartridges. No surprises there; how many other new case designs started out in .30 caliber?

If you are interested in wildcatting the .30 Remington AR or any other case for that matter, contact Dave Kiff at Pacific Tool and Gauge, www.pacifictoolandgauge.com. Dave has helped me put three wildcat cartridges together: a .416 on the WSM case, a .358 on the WSSM case and an improved version of the .35 Remington I call the .35 Super. Dave can provide chamber and reloading die reamers, but just as important he can help you sort out body taper, shoulder and lead angle issues as well as provide GO and NOGO gauges for whatever case design you dream up.