Get a wooden spoon and use the end of it or something dowel like and wrap abit of cloth around it. Then push it down the front so the the bolt assembly drops out the back.
Or if you have strong fingers you could put your finger down the breech (the bit where the balls get loaded) and see if you can push the bolt assembly out using finger pressure.
The bolt assembly is larger at the front than the back so will not push out from the other way around.
The bolt assembly is normally abit snug *which is a good thing* so giving it abit of assistance isn't a bad thing.
Will try now, errm do you HAVE to unscrew the back cap with the allen keys? Or can you just twist if with hand, because a few allen keys are missing, one of which are for the back cap. Just wondering because maybe it just needs a tiny bit unscrewing with the right allen key? I could be wrong since its spinning without an allen key anyway.