Ask the Experts - April 2011
March 08, 2011
In regard to Mr. Coffield's recent series on building a Mauser sporter, which Mauser bolt shroud from Brownells did he use?
Reid used a Brownells bolt shroud #080-000-636 in his recent series on building a Mauser sporter.
Which Mauser Bolt Shroud?
Q. In regard to Mr. Coffield's recent series on building a Mauser sporter, which Mauser bolt shroud from Brownells did he use?
--Ted Albrecht, Via e-mail
A. Brownells offers a bewildering assortment of bolt shrouds, and I should have been more specific in my column. The one I used was #080-000-636, but unfortunately it is no longer available from Brownells. However, an alternative currently in stock is the Dakota M-98 Model 70-style bolt shroud with wing safety #359-141-070, which retails for about $150. This is a nice unit that would be very appropriate for a Mauser sporter.
--Reid Coffield, Gunsmithing Editor
Q. I have enjoyed reading Shooting Times magazine. I find it informative and clearly written. I do have a question for Allan Jones about primers. I believe there is a standard or standards that were set to standardize the primer by size. I do not know who set the standards. I also do not know what unit of measurement is used to rate each size of primer. Was it thermal units of heat, explosive power, or some other unit of measurement? It does not make any difference in the real world of shooting, I am just interested.
--Larry Kilgore, Address Withheld
A. The Sporting Arms and Ammunition Manufacturers Institute (SAAMI) is the industry organization that promulgates technical guidelines for the North American firearms industry. At the root of SAAMI guidelines is the need for any cartridge made by a SAAMI member to be safely compatible with any firearm chambered for it, again made by a member company. You can learn more about SAAMI, its activities, and its mission at www.saami.org.
A point: SAAMI technical measures are conspicuously labeled "voluntary guidelines," not "standards." In spite of this, seldom does a member company sell ammo or firearms made outside these guidelines except in special cases like special military or police requirements. These would fall outside the concept of "sporting arms and ammunition." Ammo sold to the general public by member companies stays well within SAAMI guidelines.
All U.S. primer manufacturers are members. The website lists member companies. CCI-Speer is now part of ATK and therefore shares membership with Federal Cartridge.
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Based on preexisting common practice, SAAMI has published guidelines for primer and primer pocket dimensions, and it is these that create the common terms "Small Rifle, Large Rifle, Small Pistol, Large Pistol" that you see on primer boxes and reloading recommendations. SAAMI also has guidelines for primer sensitivity, again to mate firearm ignition systems with available priming technology.
SAAMI stays away from marketing issues, so would establish neither trade names nor model designations outside of the size issue. The companies came up with names like "CCI 200," "Rem 9½," etc., and the companies have to educate users through advertising, packaging, and in the case of CCI, the Speer Reloading Manual.
Neither does SAAMI set guidelines for the power of a primer. The member companies decide the technical needs of their ammo and build primers to meet that need, yet they stay with size and sensitivity guidelines. The "standard" and "Magnum" primer subdivisions are not called out in SAAMI guidelines, at least as far as I remember. (Being retired, I no longer have the massive set of SAAMI technical manuals that once graced my desk at Speer.)
There are tests, both old and new, to measure explosive power of priming mix, but the best way is to test in instrumented gun systems with common propellants and other components. Piezo-electric pressure/velocity testing with its ability to plot time-pressure curves will show the effect of the primer on the total system, not just what a dab of loose mix can do alone. This ensures that those things where SAAMI guidelines exist--pressure, velocity, accuracy, dimensions--come together to create a good cartridge.
--Allan Jones, Ballistics Editor