Quote:
Originally Posted by lclund1946
The best thing I ever did was buy a CZ 527 Kevlar, in 19 Badger, from Jim. The next best thing I did was learn as much as I could from this man via this and other articles, talking to him on the phone and picking up components in person at his shop. It was what eventually led to me developing my own wildcat cartridges and the methods I use to Develop Good Safe Loads for them. These methods work well Saami cartridges as well.
Just remember that the 17 Hornet case was designed to run at 50,000 PSI Max which is why the small rifle primers, designed for 40,000PSI, come up short and peirce. More important is to remember that the ones designed for 55,000 PSI cases, especially the CCI 450 Magnum, will not show pressure signs until well past the pressure that the 17 H case will tolerate. That is also why it is possible to determine when pressures exceed the 57,000 PSI that 223cases were designed for. Get a micrometer, measure the base of a new case, and make certain that that measurement falls somewhere in between Saami Max Cartridge base diameter (0.2982") and where the Hornady FL die sizes the base (0.2973" with the die I had) without bumping the shoulder. You will have no pressure problems and the brass will last a long time.
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Here is the Saami Spec Sheet that I used to compare measurements of a new case
(black) to the first Factory fired cases
(red) from my Savage 25. The load was hot enough to fully fireform the brass which was not the case with new factory ammo in a CZ 527 last spring. I did not have a 0.240" HS bushing so used a 25 cal comparator bushing that measures 0.247". New brass had 0.012" HS compared to a fireformed brass which takes a lot of pressure to fireform. New brass stretched .0053" at the base datum, well past the Maximum case diameter of 0.2982", but still within the maximum chamber diameter of 0.3012". This indicated to me that this was an over max load for this case and I believe I was proven correct when I had a primer blow under sustained fire on a 32Celsius afternoon in the gopher patch.
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Here is a picture showing an unfired primer on the right with one, in the middle, fired just before the one that blew. The one in the middle had about 0.006" primer flow and about the same primer pocket expansion. The one on the left had what looked like more primer protrusion and the primer pocket had expanded 0.007" and the base was fully fireformed to the chamber as shown in the next picture.
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If this can happen with factory Ammo that showed obvious over pressure past the Saami Maximum Case Diameter it will surly happen with handloads. This is why I urge you to do these measurements as you do a pressure ladder described in the thread about "Finding the Accurate Load".