June 28th, 2007
There was so much interest in Sunbuilder’s 6-6.5×47 Improved Varmint rifle that we got Scott to photograph his new cartridge. With a reamer from Dave Kiff of Pacific, Tool & Gauge, this wildcat cartridge adds about 2.0 grains capacity to the 6.5×47 necked down to 6mm. The case certainly is impressive with that 40° shoulder:
That extra two grains of capacity allows Scott (Sunbuilder) to get some very impressive velocities. Scott reports that while his most accurate load has been N160 pushing the Berger 105 Match BT at about 3115, he has pushed other 105s close to 3300 with H4350 and he thinks there’s an accuracy node around 3225 fps. (WARNING–Don’t even attempt to reach these kind of speeds with an unimproved case–you won’t succeed and you could hurt yourself in the process!) With the potential for those kinds of speeds, Scott is thinking of trying another barrel that might give better accuracy with the Hornady 105s. With its plastic tip, the Amax offers better expansion that conventional high-BC bullets. As a final note, Scott wanted us to mention the project smith: “Neil Jones of ‘Neil Jones Custom Products’ built this gun, and did a really fine job! Neil also built me a set of custom dies to match.”
June 28th, 2007
In order to get exact dimensions for custom dies, and to monitor changes in the throat of your rifle, you may want to make a chamber cast. With such casts you can determine the exact dimensions of your chamber, throat, and bore (including land/groove diameters). Most chamber casts are made with Cerrosafe, a very unique compound that is ideal for the job. To cast a chamber, Cerrosafe is poured into the chamber and the first part of the throat. As it hardens it actually shrinks, allowing you to remove the cast from your barreled action. But, then what good is an undersized cast? Well, that is the magic of Cerrosafe. As it goes into its final hardening process, it “grows” back to the true bore/chamber dimensions. Brownell’s explains: “Cerrosafe shrinks during the first 30 minutes of cooling and then at the end of an hour, is EXACTLY chamber size. Cerrosafe melts between 158°-190° F.” To learn more about chamber casting with Cerrosafe, Click here for Gun collector Mark Trope’s illustrated guide to chamber casting, found on SurplusRifle.com.
MidwayUSA has 1/2-pound bars of Cerrosafe Casting Alloy on sale for just $9.99, through the end of July. That’s $8.00 off the normal $17.99 price–quite a deal. As long as you keep the alloy free of contaminents the Cerrosafe can be re-used many times, though we advise you keep your chamber cast as a reference as long as you own the rifle.