Algodoo

A decent attempt
Have you experimented with a magazine?

I believe it's In-Line 4 cylinder engine

If you up the simulation frequency it runs fine, do like 240hz, I did 600hz for memes and never saw a single malfunction

Options > simulation > simulation frequency

Unless your pc is veeery old, mine is okay-ish

pro tip: run the simulation at 240hz or more, better smoothness and less weird glitches

Up the power of the cartridges so the recoil fully cycles the gun, if it fails with cycling try cutting out the middle portion of the follower so that it's lighter and it takes less to push it and the bullets upwards.

Also recommend putting the refresh rate at 600hz (more stable, maybe that soolves the issue of the bullets getting stuck inside the gun).

Couple of problems: 1) simulation frequency 9000hz is a fair bit overkill and is very laggy, suggest dropping that to 1200hz or 600hz 2) trigger doesn't really hold the hammer so when you work the lever the gun shoots on it's own, suggest more surface on both the parts