Berger’s New 6mm "Column" Bullet for Short-Range Benchrest
Berger Bullets has released a new 6mm (.243 caliber) bullet for short-range (100-300 yards) benchrest applications. The new bullet (shown below right), is called the “6mm BR Column”. This name does not mean the bullet is designed just for the 6mm BR cartridge. Rather it is designed for all 6mm short-range benchrest (BR) rifles, most of which are 6 PPCs (for group shooting at least). The “Column” in the name comes from the fact that Berger has optimized the height of the lead core column inside the bullet. Testing revealed that bullets which had very uniform core column heights shot more accurately and were also easier to tune. Does the new “Column” bullet work? Well, noted benchrest shooter Lou Murdica has already used them to win a Two Gun Agg in Florida against “big name” competition. Thankfully, you won’t have to wait long to try these bullets out — Berger says the new 6mm BR ‘Column’ projectiles will be available in mid-March, 2012. Call Berger at (714) 447-5422 to order.
Bullet Characteristics — Accurate and Easy to Tune
Berger’s Ballistician and lead bullet designer Bryan Litz says this new ‘Column’ bullet should be less sensitive to seating depth: “We worked very hard to produce a bullet that has a wider ‘tuning window’ for peak accuracy. This means there may be several seating depths where it shoots well. We also expect that it can shoot well at different speed nodes, but this will be dependent on your barrel.” The estimated G1 BC for these bullets is 0.277. The meplat is 0.062″, typical of benchrest bullets in this weight class. There is a small pressure ring in the bullet. Recommended twist rate is 1:13.5″ but the bullet should stabilize in a 1:14″ twist-rate barrel.
Berger’s Eric Stecker tells us: “There have been benchrest bullets in the past which were well-known for achieving consistently small groups over a wide tune range in many rifles and loads. One example of this was the Euber bullet. The seemingly ‘magical’ performance of these bullets has been attributed to special dies, stars aligning, owl feathers, or some other unknown influence. However, Bryan Litz has found that there are specific mass balance and aerodynamic properties which allow a bullet to mitigate dispersion and shoot precisely over a wide range of imperfect launch dynamics.”
Dispersion Mitigation in Bullet Design — Bryan Litz Explains
The science of dispersion-mitigating bullets is understood, but until now, no one has ever deliberately designed a bullet that has these specific attributes. There have been other bullets which have accidentally achieved the partial effect and the resulting bullets became very well known. Three key things are required to develop an effective dispersion-mitigating bullet:
1. The knowledge required to design a dispersion mitigating bullet.
2. A bullet-maker with the ability to fabricate the design precisely.
3. The means by which to test the bullets extensively to determine optimal configuration.Berger’s 6mm ‘Column’ bullet is specifically designed to mitigate the component of dispersion related to alignment. Variables related to bullet/bore axis alignment include tight necks, turning necks, bullet jump, chamber concentricity, powder charge, and so on. These are all variables which will be less critical for the new Berger 6mm ‘Column’ bullet.
To be realistic, these new bullets only mitigate dispersion effects related to axis alignment, NOT aiming error, wind deflection, or poor shooting.
Four Years of Prototype Testing
Yields Superior Bullet Design
Using his knowledge of design factors that mitigate (reduce) dispersion, Berger’s bullet designer Bryan Litz went to work creating a bullet design that had a wide, forgiving tune range. This means that the bullet shoots well with a wide variety of loads and seating depths. Bryan came up with three different shapes. Then for each of these three bullet profiles, Berger tested three different core column heights to identify the truly optimal design. Over the next four years, Lou Murdica shot thousands of test rounds in the data capture phase of the project. When testing concluded, one bullet proved to be head and shoulders above the others in its ability to shoot well at the widest variety of loads and seating depths.
The prototype bullet design that shot best in Berger’s tests has entered production as the new Berger 6mm BR ‘Column’. You’ll notice that there is no listed weight. Berger doesn’t list weight because Berger learned that the bullet’s mass is not as important as the overall balance of the bullet, which is achieved with a specific internal lead column height. Due to slight variations in copper and lead material batches, one lot may weigh 64.8 gr while another lot might weigh 65.1 grains or 64.6 grains. Berger says: “So long as the column of lead is the correct height to achieve the desired balance” the bullets should perform, no matter what the average weight of a given lot of ‘Column’ bullets may be. That said, when loading for a match, you’ll want to load all your ammo with bullets from the same lot.
Berger is now accepting orders for the new 6mm BR ‘Column’ bullets. The first lots should be available around March 16, 2012. Call Berger at (714) 447-5422 for pricing info or to place an order.
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Tags: Benchrest, Berger Bullets, Bryan Litz, Dispersion Mitigation, Eric Stecker, Lead Core, Uniformity
I find this a very interesting and informative read. In 2002, I commissioned Ferris Pindell to come up with a meplat closing die to recapture and uniform the BC lost from meplat trimming with the tool developed by David Tooley and Scott Fletcher.
Ferris worked night and day on the development of the die for almost a month. During the process, and my testing of the 300 grain MK’s, we found the core to come right up to the meplat on some bullets, and fall short on others — “out of balance” according to Ferris. So, he made me a mini-lathe to uniform the inside of the meplat, thin the inside of the meplat for easier pointing on the thick jackets, and uniform the cores. My informal testing at Hawks Ridge between 2002 and 2004 indicated that the bullets with the uniformed cores were more accurate and the vertical more repetitive on the bullets with uniformed cores — “columns” as Bryan calls them.
Berger has once again stepped to the forefront in providing the competitive shooter with a product that is well tested in the search for the ultimate in rifle accuracy. My hat is off to Bryan Litz and Berger — once again. They never stop producing a superior product because they never stop being students of the game.
Jim Hardy
What a great article. As a custom bullet maker who sometimes manages to find time to make 155 gr Palma bullets on my set of Simonson carbide dies, I understand the steps and procedures of making custom bullets.The most critical step in the process is the core seating process and when it is done right, the core height in the jacket will always be the same unless a very light core was accidentally seated in which you would feel no resistance in the seating step and discard that bullet or if a overly heavy or long core was accidentally seated,it would more than likely “pop” the jacket in half from the extreme pressure. Thus, the core should be exactly the same in all of your bullets when using the same lot of lead and jackets.
What I think that Berger and Brian are achieving with the Column bullet is not a consistent core height in the jacket so much as it is adjusting core height to achieve a optimum center of gravity for the bullet given the design parameters of the bullet shape and length .
However, I could be wrong also.
Nonetheless, a very insightful read.
Roy
Bryan Litz will CHANGE THE WORLD!!!
Roy,
That’s how I interpreted that article also. They tested 3 different core heights/lengths until one proved the most tunable between different rifles. This was a suggestion by my bullet die maker as well. I think he depicted what you’re describing as a “lead line”. Of course variations in individual core length could change that “lead line” measurement as well as cup thickness on the base of the bullet. So its definitely something to play around with as a hobbyist bullet maker.