[R.W.Dale]

In this case a Star BM in 9mm. I'm having a problem with the slide locking back intermittently and not just after the last round. It does this with any mag Ive tried it seems to me that there's not enough detent on the slide lock mechanism itself.. Please help me troubleshoot and hopefully fix this without resorting to a gunsmith

[average_shooter]

First thing to check, which also happens to be the cheapest, is your grip. It's possible that your thumb is bumping the slide stop during recoil, happened to me a time or two. Engaged the safety a couple times the same way. Once I worked out a proper grip the problem was solved.

On my 1911 slide stop there really isn't a dent for the detent to "lock" into. It's just a spring in the plunger that pushes against a pin that pushes against the slide stop to keep some tension on it.

The only other thing I can think of off the top of my head would be to get a set of new springs, or at least a new plunger spring, and swap it out, see if that helps. But a stronger plunger spring is also going to make the thumb safety harder to engage and disengage because the same spring pushes in both directions.

[R.W.Dale]

First thing to check, which also happens to be the cheapest, is your grip. It's possible that your thumb is bumping the slide stop during recoil, happened to me a time or two. Engaged the safety a couple times the same way. Once I worked out a proper grip the problem was solved.


I shoulda added that this was my first suspicion but it even happens with my thumb well away

[rcmodel]

It may be the shape of the bullet you are shooting.

The Star BM was designed & made before there was anything much except FMJ-RN ammo in use.

Todays ammo may use a different bullet shape, especially in JHP, and they can hit the slide stop inside the gun and knock it up into the locked position.

Carefully check the part of the slide stop that projects inside the mag well and see if there is any brass tracks on it from bullets in the magazine contacting it.

If there is, you can either change to a more rounded traditional bullet shape, or carefully file off enough of the slide stop to clear the bullets, but still function when the magazine follower lifts it after the last round has been fired.

rc

[R.W.Dale]

Rc


Believe it or not that was my first suspicion I have reprofiled the inside of the latch to an extent with no luck, and as it stands all I've been shooting is 115g FMJ

[Ridgerunner665]

Pics of the detent on the slide stop???

How stiff is the plunger spring???

[R.W.Dale]

Pics of the detent on the slide stop???

How stiff is the plunger spring???
You turned out to be on the right track.

After very close inspection of the slide lock "detent pin" <made up term> was worn and loose. So I removed it deburred the thing, drilled a divot for slide stop detent plunger to snap into and indexed the thing apoun reassembly (locktite and fishing line). Now the slide stop wants to stay down and takes a fair push to pivot upward which is the opposite of before. Best of all this mod is virtually invisible.

I took her for a spin and had 0 malfunctions through 5 8rd mag dumps with various bullets including JHP

Thanks fellas

[Ridgerunner665]

Glad you got it sorted out....you're welcome.

[R.W.Dale]

Glad you got it sorted out....you're welcome.
Just to clarify for others this turns out to be a part where the STAR BM differs greatly from a 1911

[Ridgerunner665]

Yep...greatly.

No external plunger tube...the plunger spring is in the slide stop itself.