March 3rd, 2018

Thunder for Down-Under — Twin 30 BR Score Benchrest Rigs

30BR Hunter Class Rifle
This story, from our Gun of the Week Archives, offers a good intro to the 30 BR cartridge, which is still the leading chambering for short-range Score Benchrest.

What’s better than one custom-built 30 BR with gorgeous wood and top-shelf components? A matching pair of course. Just ask Australian shooter Greg Roche (“Caduceus” in our Forum). A decade ago, Greg spent two years living and working in the USA. While in America, he commissioned two matched custom rifles to bring back to Australia for Hunter Class BR matches. Though the look-alike rigs are both chambered in 30 BR, one is designed for the Australian “Traditional” centerfire Hunter Class (10-lb limit), while the other is purpose-built for the “Custom” centerfire Hunter Class (14-lb limit). The 10-lb Traditional rifle features a fully-functioning two-round magazine and a 6-power scope. In contrast the Custom Class rifle is a single-shot action, with a 45X Leupold scope. The Custom weighs 13.5 pounds so it can also be used in traditional Heavy Varmint Benchrest matches if desired.

30BR Hunter Class Rifle

Tale of Two Rifles
Story and Photos by Greg Roche (“Caduceus”)

The USA boasts some of the finest precision rifle-builders and Benchrest parts suppliers in the world. Before returning to Australia after two years in the States, I decided to have two special BR rifles built using American components and skilled labor. I wanted a matched pair–twin guns that would be as handsome as they were accurate. The heavier gun of the pair, the 13.5-lb Custom Class rifle, features top-of-the-line (but well-proven) technologies and components. With the 10.5-lb Traditional Class rifle, we had to develop new solutions to allow the 30 BR cartridge to feed from a functional two-round magazine. Here is my saga of how my twin 30 BRs were conceived and built, and how they have performed in competition.

30BR Hunter Class Rifle

BACKGROUND — The 30 BR for Score Competition

The 30 BR is a wildcat cartridge based on a necked-up version of the 6mmBR Norma case. It originated in U.S. Benchrest circles where it found its niche in Varmint For Score (VFS) matches. Unlike traditional Benchrest, where group size determines the winner, VFS matches are shot on a target with multiple, concentric-ringed bullseyes. Point total is based on “best edge” shot location (one shot per bull). In score competition, the 30 BR’s “supersized” .308-diameter hole offers an advantage over the 6mm hole created by a 6 PPC, the dominant group BR chambering.

30 BR cartridge

The starting point for loading the 30 BR wildcat is Lapua 6mmBR brass. These are necked up as a single-step operation using a .30 caliber tapered expander ball (or dedicated expander mandrel). This will leave a bulge in the neck, so the expanded case neck is normally turned to bring the thickness down to the correct dimension for the chamber. I turned these necks down to .010″ wall thickness using a Stiller neck-turning tool. It features an eccentric mandrel similar to the Nielson “Pumpkin”. Loaded rounds measure .328″ neck diameter. This gives minimum clearance in my .330″ neck chamber, so very little neck resizing is needed after firing. Cases are trimmed to 1.500″ prior to turning to ensure consistency since the Stiller tool indexes the length of cut off the case mouth. Other than that, cases are just chamfered, loaded and made ready to shoot. No special fire-forming is required.

17-Twist Barrels for Both Rifles
Texan gunsmith Mike Bryant chambered both barrels. Mike also polished both barrels to a high-gloss to match the receivers. In this game, barrels are consumables, much like powder and primers, so most owners wouldn’t bother to polish their barrels. However a 30 BR barrel can provide up to 5000 rounds of accurate life (unlike a 6PPC barrel which might be tossed after 800-1000 rounds.) So, these barrels are likely to be on the rifles for many seasons. Given the high-gloss finish of the Grizzly actions and the beauty of the Red Cedar stocks, it would have been an injustice to leave a dull finish on the barrels.

The chambers were both cut with the same reamer supplied by Dave Kiff of Pacific Tool and Gauge. Randy Robinett, one of the originators of the 30 BR wildcat, specified the reamer dimensions. Randy’s 118gr, 10-ogive custom BIB bullets and the 30 BR cartridge enjoy a winning track record in the USA. The 30 BR Robinette reamer has zero free-bore and a .330″ neck, and is optimized for the BIB 118s. The bullets perform best when seated far enough out to jam firmly into the rifling as the bolt is closed. The long ogive means the bullet’s bearing surface is very short.

Slow Twists for Maximum Accuracy
You may note the unusually slow twist rate of both barrels. In most .30-caliber chamberings, the barrel twist rate is 1:11 or 1:12 to stabilize 150gr to 200gr bullets. The 30 BR is optimized for 115gr to 118gr flat-base bullets and 1:17 provides sufficient stability at muzzle velocities around 2900-3000 fps. In competitive Benchrest, where every thousandth of an inch counts, over-stabilization of projectiles can hurt accuracy, so “just stable enough” is the goal; hence the 1:17 twist.

Case Forming, Case Prep, and Reloading Methods

Sinclair Neck Micrometer, 30 BR Neck Turning
A Sinclair case neck micrometer indicates neck thickness of 0.010″ after neck turning.

Sinclair Neck Micrometer, 30 BR Neck Turning30 BR dies are readily available from a number of manufacturers. I personally use Wilson neck and seating dies with a Sinclair Arbor press, but Redding and Forster both supply high-quality threaded dies for use in a conventional press. For under $100.00 US, custom full-length dies can be obtained from Hornady and CH Tool & Die by sending them reamer prints or a couple of fired cases. Harrell’s Precision offers “semi-custom” dies. Just send them some fired cases and they select a pre-made CNC-cut die that ideally fits your chamber. You can ask the Harrell brothers for a die that’s tighter at the shoulder or base, or otherwise customized to your preferences.

Load Development and Accuracy Testing
With cases formed and bullets selected, load development is simply a matter of choosing the right primer, powder and charge weight, and loading the most consistent ammunition possible. The Lapua BR cases use a small rifle primer. The choice here was Federal 205 Match primers vs. CCI BR4 Benchrest primers. Some shooters have also had success using CCI 450 Magnum primers but it is very unlikely the small case needs this much spark to light off regular extruded powders. In my case, I selected Federal primers because availability tends to be better in Australia.

The relatively large bore-to-capacity ratio of the 30 BR case means that fast burning powders are the order of the day. Once again, US experience suggests H4198 (the Hodgdon equivalent of ADI AR2207) is the choice of match winners. The fact that H4198/AR2207 is an Australian-made product is an added bonus. So, I loaded up test rounds with AR2207 from 32.5 grains to 35.0 grains in approximately 0.3 grain increments. All bullets were seated to jam +0.010″ into the lands. This places the bullet base about two-thirds of the way down the neck and well short of the neck-shoulder junction.

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