I was thinking the other day....

[Partisan1983]

Has there ever been a small arm manufactured, that once the last round is fired a bolt hold open mechanism of some sort keeps the bolt/slide locked back, and as you eject the empty mag and put a fresh one in, the bolt or slide automatically goes into battery?

That would be much quicker than having to hit a button/tab/lever....

[vit]

A lot of pistols will do that if you slam the mag in hard.

[Sergi762]

I could see someone doing that for an AR fairly easily. AK? FAL? Hell no but then again that's plastic versus steel.

[Partisan1983]

A lot of pistols will do that if you slam the mag in hard.

But were they designed that way?

[Schuetzenman]

But were they designed that way?

No, that would be the result of a weak slide stop spring.

[ready]

My glocks always did it.

[NextGen]

My HK P2000 does this. Although I thought I read or heard somewhere that it was designed to do it.

[dfariswheel]

Not exactly what you have in mind, but the Thompson SMG fires from an open bolt.
When the last round fires, the bolt just stays locked open.
To continue firing all you have to do is insert another magazine and pull the trigger.

Some pistols were designed to close when a magazine is inserted.
One example is the Mauser HSc. The slide locks open on the last round. When a magazine (loaded OR unloaded) is inserted the slide closes and chambers a round if one is in the mag.
This is a rather odd slide stop system in which any time the slide is opened, unless the mag is loaded the slide locks open.
To close the slide you have to insert a magazine, again loaded or unloaded to close the slide.

I have read about pistols, rifles and some full-auto weapons that automatically close the bolt when a magazine is inserted but offhand can't remember what they were.
There are some semi-auto shotguns that automatically close the bolt when a shell is inserted into the magazine.

[Aggressive Perfector]

A lot of pistols will do that if you slam the mag in hard.

My Glock 19 is "bad" about doing this. Pretty much every reload, and I don't even gotta slam it (muzzle discipline is good!).