The gun only has about 500 rounds on it
Yes it jams for other people ( i not limp wristing it
No its not dirty and its lubed.
The mags are stored empty.
The mags are new They only have 50 rounds on them.
I tried stretching the springs (not clipping them.)
James on the next to last round or last round..
I have a BT380 (single stack with 6 rds) .......and a BT380 Plus (double stack with 15 rds)
My Plus version has the Mag Release at the bottom rear corner of the trigger guard, like a 92 or a 1911, but the single stack has the mag release located about an inch or so higher, just below the slide release lever.
The only relationship I could find that seemed to connect all your dots was the location of the mag release pin on the single stack
because no matter what mags you put into them, the stamped steel follower always seems to present its forward lower leg right there at the magazine release right at ....... you guessed it, ....... when the next to last and the last rounds are presenting themselves. It's the only place where the operation of the magazine is not part of the magazine; it's in the pistol itself.
You can experiment operating the mag release and you'll probably find that it releases about halfway through depressing the button. You could try firing it while depressing the button just shy of that point ........ OR you could tightly duct-tape your mag to your handgrips and just depress the mag realize when firing. If the problem stops, I would guess that the detent portion of your mag release pin wasn't cut far enough to the right (with respect to the frame) to also clear the follower.
I've never taken one out, but it appears to be a simple in and out, with the screw on the right side of the frame near the upper corner of the trigger guard.
That all I can think of.