Mate just go for it, I shot the 2018 NSS masters comp with an open sights HW77 and had a great day out,,

I returned a crap score right enough but that wasn't the point, I shoot comps for my own enjoyment and not for league standings or bragging rights.
Im not the greatest shot and I'll never win a medal (unless Im the only one entering) but I really enjoy meeting my mates and having a bit of banter with them.

Just get out and don't take it too seriously, you'll have a great time