Just bought the 5819 and searched the earth for it. Paid 1159.00 and I ax shipping come up to 1200 plus. But I’ve really wanted it for a year. Got tired of waiting and went searching. Alaska. The only state i found to have any. I even called Ruger. Asked where they shipped the last load of them and tracked one down. Whew i better like it.
Suggest you clean your new Mini, removing all the internal and external preservative they come with--it's everywhere. Then lubricate it properly; search "brownells mini-14 videos".
Shoot it a lot, in order to 1) sight it in, 2) verify 100% reliability, and 3) to test many different types of ammo to see which one(s) your Mini "likes". Take GOOD notes on the accuracy of the ammo and buy what you like.
Since Ruger takes a very dim view of user-done modifications, hold off on such until you are certain the Mini won't need to be sent back to Ruger; likely not needed
In the meantime, get a muzzle guide that slips over the muzzle and protects the bore/crown from damage done during cleaning.
Concur with genuine Ruger mags being the least troublesome.
Best of luck to you!