June 20th, 2007

Adapting RCBS Precision Mic for 6BR and Similar Cases

The $35.00 RCBS Precision MIC is a well-made and useful tool for measuring cartridge headspace and bullet seating depth. The Precision Mic measures from a datum point on the case shoulder to the base. Unfortunately the Precision MIC is not specifically made for the 6mmBR Norma, 22BR, 6XC or 6.5×47 Lapua cases. Don’t despair. Reader Caduceus has devised a clever way to adapt a .308 Winchester Precision Mic for short cases that match the .308 Win in rim diameter and case body diameter. He simply creates a spacer out of a pistol cartridge. He trimmed a 9mm case to 0.511″ and “found this to be a perfect fit which gave a zero micrometer reading when the FL-sized 6BR case was placed in it.”

RCBS Precision Mic 6BRCaduceus explains: “I can use the 308 version of the RCBS Precision Mic to compare brass which has been fully sized in my 6BR body die with brass which has been fired in my chamber. With the spacer inserted, FL-resized cases mic 0.000” at the datum point on the shoulder. Using the same set-up, fire-formed cases measure +0.005”. In other words, my chamber has a headspace of +0.005″ above minimum dimensions. This is fairly typical of a custom rifle set up for switch-barrel use. If I were to FL-resize my brass down to minimum spec each time, this excessive working would shorten its life-cycle and might lead to case head separation. Now that I know the headspace of the chamber, I can substitute the standard shell holder on my press with a Redding +0.004” competition shell-holder. This ensures that my cases only receive 0.001” of shoulder set-back.”

Click HERE for a full article explaining how to adapt an RCBS Precision Mic for use with a 6BR. You can do the same thing with a 6XC or 6.5×47 case–just cut the spacer to a shorter length (for an 0.000″ mic reading). Note: You can also use this procedure with an RCBS .243 Winchester Precision Mic.

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June 20th, 2007

Good Resource for AR15 Shooters

On the Guns & Ammo Magazine website, there is a feature article, America’s Rifle: the AR, that AR15 shooters will enjoy. The article contains dozens of links for AR15 components and accessories, including barrels, upper and lower receivers, sights, optics, grips, stocks and more. You’ll find photos of many of the more propular add-ons such as folding stocks, accessory rails, and red dot sights.

For those times when the AR stumbles (yes, it does happen), the article provides a helpful Jam-Clearance procedure. You’ll also find an excellent Trouble-Shooting Guide for the AR’s five most common problems: insufficient extractor tension, loose carrier keys, improper headspace, failure to eject (FTE), and primer issues from hot loads.

AR15 Most common problems

If you’re a black rifle shooter, definitely check out this story. It’s worth the read for the extensive product/vendor links alone, not to mention the fix-it tips.

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