October 23rd, 2012

New ‘Accuracy and Precision’ Bryan Litz Book is Shipping Now

As we reported a few weeks ago, Bryan Litz has written a new book, Accuracy and Precision for Long Range Shooting. We know many readers have pre-ordered Bryan’s latest book. Here’s the good news. Bryan reports that most pre-orders for the new book shipped yesterday, and the rest will go out today.

Litz Accuracy Precision Long Range Shooting Book

We asked Bryan to explain the differences between his original Applied Ballistics for Long Range Shooting resource book and the new Accuracy and Precision book. Here is Bryan’s explanation…

The first book, Applied Ballistics for Long-Range Shooting, covers the elements of long range shooting and explains how all the various mechanisms of external ballistics affect trajectories. It’s also the book that contains detailed drawings, BC and stability data for hundreds of bullets.

The new book, Accuracy and Precision for Long Range Shooting explains the impact of external ballistic effects in terms of “hit percentage”. For example, if you choose to ignore Coriolis Effect in your ballistic solution, how much will your hit percentage be reduced on a 10″ target at 1000 yards? How about a 5″ target at 500 yards? How much would your hit percentage be improved on a 15″ target at 1200 yards if you reduce wind uncertainty from +/-3 mph to +/-2 mph?

There are also numerous performance comparisons between different classes of cartridges. For example: how much higher is hit percentage for a .338 Lapua Magnum than a .308 Winchester for common environments and targets?

The new book identifies accuracy and precision effects and defines their effects separately. Did you ever wonder why it’s so easy to shoot a 10 inch GROUP at 1000 yards, but how difficult it is to HIT A 10″ TARGET at 1000 yards on the first shot? Shooting a 10 inch group is precision, but centering the group is a challenge of accuracy.

It’s quite common for long range shooters to focus 90% of their effort on the precision aspect, and only 10% on accuracy. To actually hit targets, you need a balance of accuracy and precision, with accuracy becoming increasingly more important as range is extended. — Bryan Litz

Permalink New Product, News 2 Comments »
October 23rd, 2012

Tech Tip: Same Load Varies in Velocity with Different Barrels

Put the same load in a variety of barrels (with the same length and chamberings) and you’ll see a wide variance in muzzle velocity. In fact, it’s not unusual to see up to 100 fps difference from one barrel to the next. We demonstrated this with a comparison test of Lapua factory ammo.

Chron Testing Lapua Factory Ammo
At our Southern California test range, we chronographed Lapua 105gr 6mmBR factory ammo in three different 8-twist barrels of similar length. The results were fascinating. Lapua specs this ammo at 2790 fps, based on Lapua’s testing with its own 26″ test barrel. We observed a speed variance of 67 fps based on tests with three aftermarket barrels.

barrel speed testing

Brand ‘S’ and Brand ‘PN’ were pre-fit barrels shot on Savage actions. Brand ‘K’ was fitted to a custom action. All test barrels were throated for the 100-108 grain bullets, though there may have been some slight variances in barrel freebore. With a COAL of 2.330″, the rounds were “jumping” to the rifling in all barrels. Among the four barrels, Brand ‘PN’ was the fastest at 2824 fps average — 67 fps faster than the slowest barrel. Roughly 10 fps can be attributed to the slightly longer length (27″ vs. 26″), but otherwise this particular barrel was simply faster than the rest. (Click Here for results of 6mmBR Barrel Length Velocity Test).

Results Are Barrel-Specific, Not Brand-Specific
These tests demonstrate that the exact same load can perform very differently in different barrels. We aren’t publishing the barrel-makers’ names, because it would be wrong to assume that ‘Brand X’ is always going to be faster than ‘Brand Y’ based on test results from a single barrel. In fact, velocities can vary up to 100 fps with two identical-spec barrels from the SAME manufacturer. That’s right, you can have two 8-twist, 26″ barrels, with the same land-groove configuration and contour, from the same manufacturer, and one can be much faster than another.

Don’t Demand More Than Your Barrel Can Deliver
We often hear guys lament, “I don’t get it… how can you guys get 2900 fps with your 6BRs and I can only get 2840?” The answer may simply be that the barrel is slower than average. If you have a slow barrel, you can try using more powder, but there is a good chance it may never run as fast as an inherently fast barrel. You shouldn’t knock yourself out (and over-stress your brass) trying to duplicate the velocities someone else may be getting. You need to work within the limits of your barrel.

Factory Ammo Provides a Benchmark
If you have a .223 Rem, 6BR, .243 Win, 6.5×47 Lapua, 6.5×55, .308 Win, 30-06, or 300 WM Rifle, we recommend you buy a box of Lapua factory-loaded ammo. This stuff will shoot great (typically around half-MOA), and it can give you a baseline to determine how your barrel stacks up speedwise. When you complete a new 6BR rifle, it’s wise to get a box of the factory ammo and chronograph it. That will immediately give you a good idea whether you have a slow, average, or fast barrel. Then you can set your velocity goals accordingly. For example, if the factory 6BR ammo runs about 2780-2790 fps in your gun, it has an average barrel. If it runs 2820+ in a 26″ barrel (or 2835 fps in a 28″), you’ve got a fast tube.

Permalink Gunsmithing, Tech Tip 21 Comments »
October 23rd, 2012

Set Up Your Own 10 meter Air Rifle Range

The great thing about shooting a precision air rifle is that you can practice indoors, for example in your garage or basement. All you need is a lighted room with an uninterrupted run of 10 meters (32.8 feet) and a secure backstop. Champion’s Choice, www.champchoice.com, has a neat, turn-key solution for Airgun shooters. The Gehmann 10 meter Target Set (item 180LP) offers everything you need for your own 10 meter shooting station. The set includes:

– Target holder (attaches to transport lines)
– Pellet trap with transporter wheel
– Transporter drive and cables
– Crank Drive wheel, v-belt, and mount

Gehmann Target Changer

You can place the pellet trap against any solid backstop, and mount the drive wheel to a secure bench or platform at a convenient height. The entire manual system shown above costs $175.00. Note, Gehmann also makes a motorized 10m airgun target changer (model 182). It’s made for 230v only, and to get one in the USA, you’d probably have to special order it. Still, it’s pretty slick as you can see:

Better Targets for Better Airgun Scores
Champion’s Choice and PilkGuns.com also sell German-made Edelmann 10m air rifle and air pistol targets, the best available. These high-grade targets are printed on the finest cross-grain card stock so pellets punch clean, clear holes. This allows easier, more reliable scoring.

CLICK HERE for Specifications of Edelmann Targets

Permalink Competition, Gear Review 7 Comments »