March 5th, 2012

Primers and Pressure Analysis by James Calhoon

by James Calhoon
(First Printed in Varmint Hunter Magazine, October, 1995)

Primers and Pressures

In the course of talking to many shooters, it has become clear to me that the manufacturers of primers have done a less than adequate job of educating reloaders on the application of their primers. Everybody seems to realize that some primers are “hotter” than others and some seem to shoot better for them than others, but few reloaders know that primers have different pressure tolerances.

Primer Pressure signs

Primer Pressure Tolerance
When loading a .223 to the maximum, I was getting primer piercing before I reached case overloading. I don’t know what prompted me to try CCI 450s instead of the 400s which I had been using, but I did. Presto! No more piercing! Interesting!? A primer that has a hotter ignition and yet withstands more pressure! Thats when I decided that it was time to do a dissection of all primers concerned. The chart below shows my results.

Primers and Pressures

By studying the numbers (Cup “A” thickness), one can see which primers in the small rifle sections should be more resistant to primer cratering and/or piercing. Primer cup diameters are all similar and appear to follow a specification, but check out the cup thickness in the small rifle primers (Dimension “A”). Some cups are quite a bit thicker than others: .025″ for CCI 450 vs. .0019″ for Fed 200. Large rifle primers all appear to have the same cup thickness, no matter what the type. (As a note of interest, small pistol primers are .017″ thick and large pistol primers are .020″ thick.)

If you are shooting a 22 Cooper, Hornet, or a Bee, the .020″ cup will perform admirably. But try using the .020″ cup in a 17 Remington and you will pierce primers, even with moderate loads.

Considering that cup thickness varies in the small rifle primers, it is obvious that primer “flatness” cannot solely be used as a pressure indicator.

Another factor which determines the strength of a primer cup is the work-hardened state of the metal used to make the primer cup. Most primers are made with cartridge brass (70% copper, 30% zinc), which can vary from 46,000 psi, soft, to 76,000 psi tensile strength when fully hardened. Note that manufacturers specify the hardness of metal desired, so some cups are definitely “harder” that others.

What does all this mean to the reloader?
- Cases that utilize small rifle primers and operate at moderate pressures (40,000 psi) can use CCI 400, Federal 200, Rem 6 1/2, or Win SR. Such cases include 22 CCM, 22 Hornet and the 218 Bee. Other cases that use the small rifle primer can use the above primers only if moderate loads are used. Keep to the lower end of reloading recommendations.

– Cases that utilize small rifle primers and operate at higher pressures (55,000 psi) should use CCI 450, CCI BR4, Fed 205 and Rem 7 1/2.

– All the large rifle primers measured have the same thickness. Therefore choose based on other factors, such as accuracy, low ES/SD, cost, cup hardness, and uniformity.

Hope this clears up some primer confusion. If you want more information about primers, priming compounds, or even how to make primers, the NRA sells an excellent book called “Ammunition Making” by George Frost. This book tells it like it is in the ammo making industry.

Jim Calhoon Products

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March 5th, 2012

Modular Zanotti Safes Offer Easy Installation

We’ve received inquiries from readers who are looking for a gunsafe that is big and strong but can be broken down and transported more easily that a typical 800 to 1200-lb safe. One product that fits the bill is the Zanotti modular safe. It arrives in sections, none weighing more than 170 pounds. It is assembled in place, then can be dis-assembled when you need to move. The Zanotti is also well-suited for a gun-owner who lives in an apartment up many flights of stairs.

Zanotti take-down gunsafes

Zanotti Gun safeZanotti Armor safes are ideal for gun owners who need to move frequently or who live in a location where it is difficult to position a conventional safe. Zanotti safes arrive in three or four discrete shipping boxes. The safe is assembled by the owner, on site, in six steps. The heaviest component is the door, weighing 110 pounds in the 16-gun ZAI safe, and 175 pounds in the largest 52-gun ZAIII model. Five safe models are offered, ranging from 350 to 925 pounds assembled weight, without interior. Zanotti safes are popular with military personnel and others whose jobs force them to re-locate often. The safe can be assembled in under 30 minutes with no tools other than a hammer, and all you need is a hand dolly to move any component.

Guns Magazine reports: “The panels are interlocked by 3/8 inch, nickel-plated steel “L” shaped pins that slip into steel tubing sections welded to the interior surfaces of the panels. The slip fit is held to a tolerance of .003 inch, and the safes are completely assembled and hand-fitted at the factory to insure the panels will align properly. The body is made from 1/8 inch and 3/16 inch steel; the door from 3/16 inch steel; the locking bolts are 3/4 inch steel.” This is heavier gauge steel than you’ll find on most conventional gun safes.

Zanotti offers many deluxe interiors including a system of roll-out sliding drawers in the bottom of the safe. We think the sliding drawers are ideal for storing handguns and expensive items such as cameras and binoculars that you want to keep out of plain view. Mark Zanotti, the innovative creator of these modular safes, can also customize any interior to suit the customer’s particular needs.

Editor’s Note: For most applications, a conventional safe is still the best choice. Bolted in place, a conventional safe with welded walls will provide the best security and a conventional safe can provide increased fire protection. Zanotti safes do not employ a separate layer of sheet-rock or ceramic fire lining. The Zanotti is a special product for gun-owners with special needs. The units are well-made and Zanotti offers many nice custom interior features that you won’t find even on much more expensive conventional safes.

To learn more about gunsafe features and fire-proofing, read our Gunsafe Buyers’ Guide.

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