"Regulated", as in, fitted with a regulator. A device that regulates the pressure of the air upstream of the inlet valve, and is supposed to make the shot-to-shot consistency a lot better. The idea is that it takes out the variation caused by the inlet valve having to work against a higher pressure at the start of the charge and then opens for longer toward the end of the charge.
Also, the most problematic and cussed piece of kit fitted to a pcp.
Modern UNregulated rifles like the AA S400 don't really need them. As long as you are prepared to learn where the most consistent section of the charge is then a regulator not required as you only get 10-15 fps variation within that. An S400 charges to 190bar, but you probably dump the first 10 shots, then get 50-60 "good" shots before the charge start to be exhausted. A regulated rifle would probably give you 80-90 shots across the charge.
My comment on an unregulated carbine is that the cylinder is smaller, so the number of consistent shots come down. Regulated rifles cost more and have more problems.
Jerry
If you are looking at dropping quarry then a multishot is way better than a single shot PCP which is way better than a break barrel or under lever springer/gas ram.
Side lever is also better than bolt action imho depending on make/model
There is NOTHING wrong with the AA magazine system. Very reliable.
The issue with AA mags is they are prince Charles sticky out so saddle clash and some scopes will not be happy. Plus being enclosed and full of spings, then crud build up can be a factor.
The best multi shot mag system is still the HW100 system Inc. the single shot adapter.
Air arms regs... hmmm.... I am not convinced they have really nailed it tbh.
Their knock open valves are fine... but you need to know your sweet spot. You do your part and the valve will do its part.
A reg is better in terms of flat lining consistency imho (when they work) but the knock open will serve you well.....
In a battle of wits I refuse to engage with an unarmed person.
To one shot one kill, you need to seek the S. Kill only comes from Skill