For a GBBR, an open bolt is the way to go. If you have ever stripped a real semi/auto rifle, then the mechanics behind an open bolt is not very different.
Although people say that GBBRs are problematic, once it has been upgraded, they can be as reliable as an AEG once in play. Upgrades usually include an NPAS and steel replacements for hard-wearing parts (mainly in the trigger group). Their advantages includes easy maintenance/repair, no electrical gremlins and realistic behaviour. Their disadvantages are limited load (real/low caps), magazine cooldown, weight (mostly because of magazines), often potmetal parts when they should be steel, and slower reloading.
Just like AEGs, GBBRs may require internal upgrades out-of-the-box to make them reliable/gameable. Also, like AEGs, once a GBBR goes down in the field, there is the strong possibility that it will be out for the rest of the day if repairs are not possible.
Footnote: I purchased a used GBBR several weeks back via ASC that was partially upgraded. I completed its internal upgrades and have since fielded it with good results. Of course, I don't ever expect anything to work reliably out-of-the-box - even my AEGs have had to be tinkered with for reliability. Your mileage will vary.
VFC SCAR-L - VFC SCAR SSR - KJW Hi-Capa 5.1 - CAW M79
The Three Sisters - WE G39 E/K/C
Originally Posted by kalnaren
Stalker stays where he is.
His BB's fly across the country to hit their target.