6mmBR Loading for Newbies
One of our readers has been shooting his 6BR with considerable success in tactical/practical matches. Thus far he’s been using Lapua factory-loaded 105gr ammo. The factory ammo has delivered superb accuracy for him — under 1/4 MOA at 100 yards. Now, he is making the jump into reloading. He asked for some tips on working up a good load for an 8-twist 6BR with a no-turn neck, and selecting reloading tools. Since other readers may be 6BR novices as well, here are some helpful hints…
Accurate Reloading Tips for the 6mmBR Cartridge
• Brass Prep — You need to look at the flash-holes to make sure they’re not occluded. A few lots of Lapua brass came with a little sliver/flake of brass in the hole, sort of like a quarter moon. You can clean that up with an inexpensive pin vise. Otherwise, there is no need to ream flash holes or uniform primer pockets.
• Neck Chamfering — You want to develop a good feel for neck chamfering. You don’t want/need to remove a lot of brass — just knock off the sharp edge. I use a Forster 45 deg “rocket” tool. It works fine. After a couple light turns, spin backwards to smooth the cut and then finish with a twist with a green scotch pad. If you use a deep-angle chamferer, be very careful not to overcut and remove too much brass.
• Neck Tension — On brand new, unfired Lapua 6BR brass, neck tension is excessive. You should run an expander mandrel down the case necks before the first firing. This will reduce the neck tension while it fixes necks that may be dented or out of round. After the first firing, we suggest sizing the necks so that, after they come out of your sizing die, the neck outside diameter (OD) is .002″ less than the neck diameter of a loaded round with bullet seated. If that doesn’t work, try one smaller size bushing for .001″ tension. Many top shooters like low neck tension, but we’ve also seen heavy tension work. The .002″ under loaded OD is a good starting point with the 6BR.
• Primers — A lot of guys like the CCI 450 primers. They’re a lot cheaper than the Federal and CCI BR primers and may give a little more velocity. The cups are also hard, which lets you run faster loads with less concern about cratering. Wolf/Tula primers also have hard cups, but you must make sure to seat them deep enough.
• Load Development and Bullet Choice — With the 6BR and 100-108gr bullets, load development should be relatively easy. With Varget, Reloder 15, Norma 203B, or VV N150, between 30.0 and 30.7 grains should work as your final load. My match load is 30.3 Varget and that has shot under 2.0″ at 600 yards. Start at 29.0 grains and and work up in 0.2 grain increments, checking for pressure. DO weigh every load… twice. If possible, use a chronograph during your load work-up. 2880-2920 fps is a nice “sweet spot” for the 6BR, but slower can be very accurate too. (With custom actions, tight chambers, and long barrels, some guys are going even faster — but that’s hard on brass.)
If you have a barrel on the slow side, consider shooting the Berger 100gr ‘Match Target’ BTs. These bullets are very accurate, and we’ve found that you can drive them 75-100 fps faster than the Berger 108s or Sierra 107s at similar pressure levels. With the 100-grainers, you may find that you can hit a superior velocity/accuracy node, so they may shoot better overall than the 105-108 class bullets. Varget, RL15, and IMR 8208 all work great with this 100gr bullet.
For shooting from 300-500 yards, you should consider the lighter-weight bullets: Sierra 95gr MK, Lapua 90gr Scenar, Berger 95gr and 87gr VLD. The Sierra and Lapua bullets are very accurate and not sensitive to seating depth. In addition to the powders mentioned above, H4895 and IMR 8208 XBR work very well with the 90-grain-class bullets. One note about the smaller Berger VLDs — the Berger 95gr VLD and 87gr VLD both have very short bearing surfaces, so they work best in a chamber with a short-to-moderate Freebore. We had the best luck with the 95gr VLD about .010″ into the lands. We could achieve that with an 0.075″ Freebore chamber. But you won’t be able to hit the rifling with the 95s in a long-throated chamber. With this bullet we recommend sorting bullets by base to ogive.
For guys with 10-twist barrels, try out the new Berger 87gr VLD. It was expressly designed to work great in the 1:10″ twist barrels. Forum member Mark Schronce reports that this bullet is extremely accurate and can be driven fast. It has an 0.412 G1 BC. Note: The new 87gr VLD, product #24524, is hard to find on the Berger website, but it IS available. Berger calls it a “hunting bullet”, but it works great on paper also. MidwayUSA has the 87-grainers in stock as item #77854.
• Pure Accuracy — If you are looking for bughole accuracy out of your 6BR, try the Berger 80gr FBHP ‘Match Varmint’ bullets (item #24321). Many folks have reported these bullets will shoot in the ones and low twos, even in 8-twist barrels. For 100- to 200-yard distances, these bullets are hard to beat for pure accuracy. Beyond those distances, you’ll want something with a higher BC. We’ve had good luck with the Berger 80s pushed by Vihtavuori N135, and IMR 8208 XBR.
• C.O.A.L. — Bullet seating depth is very important. You should get the Hornady (Stoney Point) O.A.L. Gauge (shown below). This will let you discern the OAL at which the bullets just contact the rifling. The trick is tapping gently on the stick. (Get a wood dowel as the bullet can get stuck if you tap a little too aggressively.) With some practice, measuring is quick and you can get repeatable measurements of your distance to lands within .001-.002″.
A good starting point for the Berger and Lapua 105s is about .010-.015 IN the lands and then work back. Each barrel is different, but about .010″ in the lands works for many folks. One guy I know started at .012″ in the lands with Berger 105s, adjusted his load up from 30.0 to 30.4 Varget, and within an hour he was done with load dev — the gun was shooting in the low 2s. He went out and won his first match with that load the next day! With the Sierra 107s you might want to start .020″ out of the lands.
• Seating Die — We recommend the Wilson Micrometer Seating Die. The adjustable top makes it really easy to play with seating depths. Keep in mind, however, that moving 5 hash marks on the die may not give you exactly .005″ seating depth change — it will be close, but you should measure and write down the actual base to ogive length. FYI, I measure base to ogive of every loaded round. Occasionally you’ll find a bullet that ends up seated a little long or short.
NOTE: The fit of the 6BR Wilson seating die is very tight. You may have difficulty getting a fired case into the die if you do not full-length size the case first. Even if the case goes in easily and even with FL-sized cases, there may be a vacuum fit that makes the loaded round a little hard to remove. Here’s a trick — use the end of a Popsicle stick placed under the cartridge rim to lever the case out. I’ve found that the “working” end of a metal spoon works well too, but be careful not to nick the bottom of the die.