please excuse me for being a 1 time signup and poster

I've been out of paintball for 2 years since my daughter was Born.

my Brother gave me his busted up oldschool Minimag a year or so ago, and i'm just gassin' her up now.

These are the issues.

1) when first gassed up, air came out the back vent.= i stripped and oiled all o-rings. no longer leaks
-there is a big spring that looks a tad rusted

2) Now when gassing up trigger charges fine into place, but when i fire the bolt doesn't cycle back, it stays in the barrel.
- i can push the barrel back into place with a squeegee, when doing so i hear a click, almost like a sear.

little help would be great.

NOTE: this is a Stock mechanical minimag, nothing fancy

im guessing im going to need a rebuild kit either way by the end of this.

thanks yall