Former MD resident, now in West by God Virgina for a few years. I wanted to bring a few of my rifles and handguns into MD to shoot with some friends there. I left before the new laws went into effect. So I am unsure of bringing my firearms into MD now. Is this a no go now with the new laws? From what I understand my friends will be unable to shoot my handguns unless they have the new MD handgun card? I wanted to bring in my AR pistol also, but was unsure of that as before I left they were a no go then.

Or would it be best just to have them drive down here?

I'm in the same boat:  former MD resident who comes back to shoot in MD sometimes.

I have ARs I built after the ban.  I don't have and Maryland receipts proving I bought them in MD (or anywhere else) before the ban date.  

Also, I know MD guys are grandfathered in as far as magazines.  But as an out-of-stater, can I legally bring 30 round mags into MD?

I'm not a lawyer, but you're good to go on any handguns.  Do not bring any banned rifles into Maryland, that is illegal.  HBAR AR-15s are legal but to be safe just leave your evil rifles at home, it's not worth the risk or time trying to understand which rifles are banned and which are not.  You are OK bringing in magazines over 10 rounds to Maryland.  Just don't sell or give away any mags over 10 rounds, that's a crime.

ETA: this link will tell you if your rifle is banned or not.

https://www.mdsp.org/Organization/SupportServicesBureau/LicensingDivision/MainLicensingPage/LicensingandRegistration/Firearms/FirearmSearch.aspx