I've had one. Bought second hand, bog standard and bargain price. I knew the issues and bought it because it was the right price and I knew I could get it close to something good without exceeding the new price as a total spend, i.e. price of gun+price of improvements. I did exceed that by a hundred quid though. I enjoyed getting the thing 'right', but then I do like tinkering, or did back then
When I sold the gun, I lost 300 quid. That's the rub with them, it doesn't matter what you do to them, they're still an AR20 and they're still perceived as cheap n cheerful and there's no getting away from that.
I wouldn't spend 600 quid on a new one. Unsorted, they are disappointing and that might 'niggle' you.
At the end of the day though, spend your
money on what you
want to have.
I bought an EV11 for less than the total spend on the AR20, again a used gun. It had reg creep which I had mended and after that it was stunning!
Mate of mine has just sold one for 500 quid! A sorted Mk1. There are better guns for the money you've got and a big part of this wonderful sport is going to be in your head. If your gun is niggling you, you won't hit many targets. My AR20 niggled the hell out of me