I shot at Gateway for several years without a membership but had to pay higher range fees. This was 12+ years ago and policies might have changed, best to call them and see what the deal is now. Way back when you had to be a member or with a member to use the 'open' bays for action type practice, and there had to be two persons there to shoot. Non-members shooting alone had to stay on the supervised lines. LOL, and the PA they had would warn about rapid fire regularly on the supervised lines.
To enter in a match odds are VERY high that membership is not a requirement, otherwise the out of town shooters would not show up and the matches would dwindle to nothing in a hurry.