Break-in, you know, like breaking in a pair of new shoes. At first they're stiff and uncomfortable, but after a while they loosen up and become more comfortable as they conform to the peculiarities of your feet.
A new gun is composed of various parts that have been assembled in the factory and tested to make sure they operate properly, but they really need some running time to get to the point where all the parts just sort of settle in and work "happily" together. It usually means that edges and corners and surfaces have to be worn just a little smoother, and that takes shooting. In the BT380's case, shooting "ball" ammo, FMJ, will in most cases give your gun the opportunity to put a little wear on the moving parts so things work as well as it was designed. Cleaning and lubricating are also an important part of proper gun maintenance.
Some gun designs seem to require more break-in than others. Because of the limitations of the .380acp cartridge and the demands of the blow-back design of the BT380, there's a substantial break-in period of at least 200 rounds fired associated with this gun. Some people experience a few failures during this period and then the gun settles in and there are no more problems. Others don't experience any trouble at all.
There are other guns that don't need much of a break-in period at all, such as the Bersa Thunder 9 Ultra Compact, which I've had since Jan. 2007. I've never had any problem with this firearm, ever, and it's been 100% right out of the box. But it's a different design from the BT380, and uses a more powerful cartridge, and it has it's own challenges since it's not quite as small and light as the BT380.
p-t-max
I'm no expert, I'm just, well---opinionated!
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