1 shot out of group

[bobthenailer]

i have a springfield 1911 in 38 super , after inserting a new mag and dropping the slide. the first shot is high and to the left from the group ! if i dont let the slide lock back and leave 1 round in the chamber from the previous mag and insert a loaded mag all shots are in the group ? this is the only 1911 platform pistol ive incountered this with . and ive worked with perhaps 20

[Lee W]

It sounds like set bullet is getting set back in the case when you drop the slide.
The round hits the ramp differently when the slide gets dropped vs normal operation.
That would increase the pressure of the round and creating the results you describe.

[MtGun44]

My bet is a dirty or tight chamber, not getting the same headspace with
the lower slide velocity. See if a spotless chamber will make this happen
less or not at all.

.38 super has been a problem child for accy forever, in the sense that the
original design (Colt) attempted to headspace on the nearly non-existent
rim. George Nonte Jr. (a long dead gunwriter) first pioneered a .38 Super
chamber that ignored the silly little micro-rim and put a normal headspace
shoulder like .45 ACP into the chamber. Accy immediately improved to normal
1911 levels, and many (most??) modern .38 Super bbls use normal front step
type chamber and ignore the tiny little rim.

See if you can see a tiny rim cut in the hood of your barrel, and no defined
square corner at the front of the chamber (look at a .45ACP bbl to see one with
no rim cut in the hood and a definite chamber front step). I doubt that Springfield
is doing this pretty much discredited chambering style, but it might be, so it is
worth checking for. If it looks like a mini version of a .45ACP chamber, I go back
to the dirty chamber suspicion.

Bill