A 2 MOA gun is fine for 100 yards. And probably OK for 200 yards. After 200, you need something less than a 2 MOA. So for now, a 2 MOA gun for me would be borderline. I think I need a 1 to 1.5 MOA gun.
I'm a little confused on exactly what a G3 gun is. There are all sorts of model numbers out there that reference G3. Is it anything that is copying an H&K G3? PTR-91, SAR-8, SAR3/8, C308, CETME, HK91, G3S, XG3S, PTR GI, etc. Prortugese guns, Greek guns, Spanish guns, etc etc. And even after you figure out all of that, you get into the markings on a particular gun and what to watch out for. Seems like it gets complicated.
I can give you what I understand of the rifle, just accept that I'm probably wrong.
So, the roller delayed action was developed in WW2. It was famously seen in the Stg45, that was never fully completed before the war ended.
When WW2 ended, a lot of scientists and engineers from Germany moved to Spain or Argentina. Some of them took the roller delayed setup, and used it to develop the Cetme for Spain.
Germany wanted a new rifle, and liked the FAL. When they wanted to check with FN about making the FAL in Germany, problems happened. FN was owned by a German company before WW1, then taken over by Germany during WW1. And then it happened again 22 or so years later in WW2. FN basically told Germany to stick it.
Germany needed a cheap rifle to compete with the AK, because East Germany and the Soviets were on their border. That's what the G3 is by the way, not a precision gun, a western AK kinda rifle.
They talked to Spain, and to the engineers that made the Cetme. Had them come back, found HK, and make some tweaks, turn it into the G3.
Other countries wanted to make it, and so HK sold them the technical package and tooling to make their own, because most countries want to make, rather than import weapons, so that war or embargo's don't leave them high and dry.
As to the HK91, this has to do with their numbering system.
9 stands for "semi-auto rifles" and 1 for "7.62x51"
That is the civilian, non select fire version of the G3, that HK sells.
PTR, a US company, wanted to make G3/HK91's, to fill in a void in the market. They bought the tooling from Portugal, who had moved on to different weapons, and started making their own. For copyright reasons, had to be careful in how they name it.
Century got ahold of parts kits for cetme's, and had their trained monkeys turn them into the C308 abominations.
That all make sense?