Interesting thread! Slowly and surely I started working on some cast bullet designs for my pistols. This eventually led me to the 380 Auto. My initial work started with the 9mm Luger. After a never ending wait for an aftermarket non-polygonal barrel for my Glock, I bought a new Jimenez Arms JA-Nine sitting in my local gun shop's case. It was cheaper than the aftermarket barrel so I canceled the order and started working on my 9mm design with this pistol.
I've read a lot of “no-good” about this pistol and it's linage (Bryco/Jennings/Jimenez Arms) but don't mind stepping to my own beat and have since determined that those writing negatively about the pistols have no first hand experience with the pistols. My JA-Nine shot cast bullets so well, it ended up costing me more than that aftermarket barrel as I bought the entire JA lineup of pistols except the rimfire model. This led me to the 380 Auto.
Starting with a chamber cast and barrel slugging, I special ordered a Lee mold specifically to fit the sub-compact JA-380. Like all my designs, I used the services of Tom Myers' Precision Chamber Dimension software to visualize and develop the bullet. The method I use is to not dictate bullet weight at the start but rather to fill the step/leade/freebore/throat and then use center of gravity and lift to determine body length which results in weight. In the case of the 380-Auto, the results were a 125-grain bullet.
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While waiting for the molds to be cut at Lee, Jimenez Arms released a full size 380 Auto (LC-380) based on the JA-Nine frame and I was able to obtain one of the first pistols with the combat black finish.
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What is weird is that the sub-compact JA-380 shot smaller groups that the full frame LC-380. In the larger pistols defense is that this load work is the first shooting that has cycled through it. The sub-compact has has close to 1K rounds pass through it.
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With such a difference in bullet weight over the standard factory ammo bullet of 90-grains, I wondered during development if the FPS would take to great a hit with the heavier bullet. The most used comparison tool from self defense considerations is the “Hatcher” index. Despite the loss of velocity, the heavier bullet made a small gain.
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There is a price to be paid for shooting a sub compact with a large hand. Here are my “fang” marks after shooting the load work. I maintain a full grip on the stock but that slide still operates!