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Revised 12/26/00 

Case Head Analysis.

By Fred the Re-loader

1. Norma 280 Rem. 0.081"

2. Rem. 7mm-08 Ai 0.065"

3. Federal 270 0.057

4. Win. Super X 30-06 .082"

5 Win. Super X 7x57 .080.

6. Lapua 30-06 0.065

7. NATO Military 7.62 .079

8. 30-06 Imperial 0.094"

9. 30-06/ 243AI Imperial

10. Win 7mm Mauser 0.090

11. Rem. 7x57 0.074

Ratings based on my own experience from excellent to poor. 10, 6, 1,4,5, 7, 3, 11, 2 (8 and 9 not made any more) 10 hard to find or not made any more. For any Magnum conversion 300&375 H&H Winchester is the very best.

Above  are various cases that can be used to make all of the 30-06 and 308 based wildcats. Some are more suitable than others. I like to use the 7x57 case for the 308 length wildcats and the 280 and 30-06 for the standard long actions. But lately for lack of good 7x57 brass I am using Lapua 30-06 cases to make 243AI and 7mm-08AI.

Note. All cases had the primer pockets uniformed to a depth of 0.127". The dimensions are from the bottom of the primer pocket to the inside case bottom. No 8 and 10 have the strongest bottom. No 1, 4, 5 and 6 are some of the strongest cases, as far as case life is concerned.

No 2 and 6 have the same dimension but the Remington case does not hold up to repeated reloading with maximum loads. The No 7 Military 7.62 is a strong case but lacks case volume also extremely serviceable. The No 10 7x57 Mauser made by Winchester make long lasting brass for the 243 AI, 6mmAI, 260AI, 7mm-08AI, and the 308AI.

However a well known HBR shooter with championship credits makes .25 Hunter cartridges from 22-250 cases using the Remington cases. Because these cases are soft they fire form to the exact size of the chamber with a full load that reaches enough chamber expansion with little or no brass spring back for a perfect case fit. There is no problem with expanding primer pockets if subsequent reloads are loaded to slightly less pressure.

He has used 40 such cases for competition for three seasons without case failure. A case that fits the chamber exactly does not allow brass flow. We are talking about a Wildcat case with very little wall taper and a shoulder angle of 30 deg ore more.

The No 6, 30-06 Lapua brass for the 7mm-08AI with a longer neck tested really well with 1.5 gr over max, the primer pocket expanded only 0.0003" without extraction problem. Backed down to my max load there is no sign of expansion in the primer pocket. With the amount of labor involved to form wildcat brass it pays to get the best brass. I have some Norma 280AI brass that has been around for a long time.

The Reloader must remember that he can ruin any brass by overloading. Two high pressure indicators both involve the primer pocket. One expanding the pocket diameter and two flatten the primer. One will make the case useless; two is absolute max because it also pushes the bottom of the pocket up. You can tell by using a pocket uniformer for cleaning when you remove brass from the bottom of the pocket. Each time you remove brass from the bottom of the pocket you are removing a margin of safety.

As shown, the base thickness is not a reliable indicator how good the brass is for repeated maximum loads. It is wise not to use maximum loads but rather go for a good accurate load. 50 to 75ft/sec are not making any difference when you got more than you need to start with.

One other item a Reloader must keep in mind is that the stamp on the bottom of the case is not always the maker of the case. Wby=Norma or RWS or Rem- 0r? Similar with other brands one batch varies from the other in case weight and volume in spite of brand stamp. See case #5 and #10, both are the same caliber and make. Volume is 2.0 gr less in #10 and why the different name? Looks like they are not made in the same factory and or for a different country? Also both cases are excellent and strong. Case heads in #4 and #5 are nearly identical also same brand.

Some Brass Background.

Brass is an ALLOY consisting mainly of COPPER (over 50%) and ZINC, to which smaller amounts of other elements may be added. Elements such as tin, lead, silver and aluminum are added to copper in making brasses, depending upon the color, strength, machinability, corrosion resistance, and ductility desired. The mechanical properties, the tensile strength, and ductility of alloys in the copper-zinc system improve as the zinc content increases (up to 35%).

The earliest brass, composed only of copper and zinc, was made by the Romans about 20 BC, and was later used to make some of their coins. By the 11th century, it was being widely produced in Western Europe. Brasses are important partly because they are cheaper than unalloyed copper. In addition, they are more susceptible (up to about 30% zinc) to the important machining process of cold forming.

Types and Machinability.

Some brasses are more susceptible to certain machining processes than others, and these differences result in a wide variety of compositions adaptable to particular uses. Cartridge brass, consisting of 70% copper, is most popular for operations such as cold drawing (successively reducing with dies the diameter of wires, pipes, and tubes) and bending, whether in strip, rod, or tube form. (85% copper), are not so strong, but they harden slowly, permitting successive operations without intermediate annealing

 

Fred The Re-Loader

zermel@shaw.ca