April 19th, 2015

The “Long Dasher” Cartridge, Plus a Trick Rangefinder Mount

Forum member Scott S. (Sunbuilder) has built a sweet long-range varminter based on the 6.5×47 Lapua cartridge necked down to 6mm and then improved to 40 degrees, with slightly less body taper. Scott tells us that “improving the case adds about 2.0 grains to the case capacity”. This allows Scott to run the 103-108gr bullets at well over 3100 fps, with no pressure issues. Scott calls his Improved case a “Long Dasher”, a name suggested by Dave Kiff of Pacific Tool & Gauge.

6-6.5×47 Improved Works Well with Many Powders
Scott’s 6-6.5×47 Lapua Improved varmint rifle features a Stiller Diamondback action, Lilja 30″ 8-twist barrel, Richard Franklin stock, and a NightForce 8-32×56 NXS. Scott has had excellent success — his two longest groundhog hits were at 778 and 810 yards. Scott has tested many powders with his 6-6.5×47 wildcat: “I tried several powders (H4350, N160, N560, H4831sc), and primers (CCI 450, BR4, Rem 7 1/2, Fed 205Ms). I got better velocity with H4350, but my barrel likes the N160. I did find a [high-speed] node with H4350. The increased velocity potential of this cartridge is partially due to the slightly increased case capacity. The load I am shooting now is 40.5gr N160, Berger 105gr Match BT, .010″ jam, CCI BR4, .002″ neck tension at 3115 fps. This has an ES under 15 fps, and it will group under 2″ at 500 yards if conditions hold. This ‘Long Dasher’ (6-6.5×47) seems to have a lot of potential (and that’s an understatement).”

A Better Mount for the Spotter and Rangefinder
Scott designed and fabricated a very slick set-up to hold his Zeiss spotting scope and Leica CRF RangeFinder. He’s built a combo bracket that holds both units rock steady, with a parallel line of sight (same axis and elevation). Smart. Very smart. Scott explains: “I built a mount to connect my rangefinder to my spotting scope. The mount can be adjusted, so the spotting scope and rangefinder are both centered on the same object. The only way I have found to get repeatable long-range readings is to make them from a stable base.” Scott, we think you’ve got a winner here with your innovative and clever design.

sunbuilder spotting scope rangefinder mount

Permalink Hunting/Varminting, Optics, Reloading 2 Comments »
April 19th, 2015

Tech Tip: Pros and Cons of a Barrel Tuner

Barrel Tuner Gene Bukys Shadetree Engineering

Commentary by Mark Walker, Sierra Bullets Product Development Manager
This story originally appeared in the Sierra Bullets Blog. Visit SierraBullets.com.

Some people love tuners and others hate them. I use them on my rifles and I’ve had more than one person ask me why on earth I would put one of those things on my barrel. I’ve even had a national long range champion tell me to unscrew it and throw it into Lake Erie on my next trip to the pits at Camp Perry. However, there are other shooters that swear by them and have many match wins to back it up.

It’s an indisputable fact that tuners do have an effect on a rifle’s accuracy, however how much is somewhat open for debate. The large heavy target barrels that we use for benchrest or f-class may not be affected as much by a tuner as a lighter weight sporter type barrel. Each barrel that I’ve installed a tuner on not only showed improvement in accuracy but also displayed a wider load window. The increased accuracy is because of the ability to adjust the tuner to the load, however I believe the wider load window is due to the added weight of the tuner slowing down the barrel vibrations. These are both very important aspects of having a very accurate rifle.

Barrel Tuner Gene Bukys Shadetree Engineering

While better accuracy and a wider load window are two areas of improvement, I believe the most important feature of a tuner is the ability to adjust the tune during the middle of a match. This is especially important during matches where you must load all your ammo earlier and cannot make adjustments to the load during the match. If you happen to miss the load, instead of having to deal with a gun that isn’t shooting you can make an adjustment to the tuner and hopefully improve the accuracy of the rifle.

While I’ve laid out several ways that a tuner can help, there are also a few ways that tuners can cause problems. They add weight so if you are shooting a discipline that has weight limits on the rifle, you may not be able to install a tuner and still make weight. Sometimes, a barrel just doesn’t show improvement with a tuner installed. These are few and far between, but it is something to consider. If you make an adjustment to the tuner in a match, you need to make sure you move it in the right direction. Adjusting a tuner in the wrong direction can cause very large groups. And finally, if they aren’t tightened properly, tuners can come loose during firing which will cause a lot of problems as well.

As you can see, tuners have both positive and negative aspects. In my personal experience, the positives far outweigh the negatives so I will continue to use them on all of my competitive rifles. If you’ve been thinking about installing a tuner, hopefully some of the information that I’ve presented will help you make an informed decision.

Barrel Tuner

Permalink Competition, Tech Tip 2 Comments »