What kind of Gammo do you have? I have a Mach I nitro in .177 that shoots .5 in groups at 50yds using Crosman Piranha's and will do the same with H&N FTTs. I also have a Varmint that was a springer untill I converted to to a nitro via Australia Custom Seals. I also put on of their seals in it and it shoots as well as the Mach I. My Urban 22 (BSA Made) will out shoot my hold capabilities. I have it mounted to a Tripod and "Urban Snipe" out my kitchen window. It loves H&N Field Target Trophy 14.66 copper plated or pure lead at a respectable velocity. The lead at 839 fps and the coppers at 880 fps. I have killed many Tree Rats with it at ranges out to 45 yds with the FTTs and several crows at max 55 yds with H&N Barracuda Power 21.4g at 690 fps.
The weapon you choose depends on what you want to do with it. What is the max range you normally use it? How much are you willing to spend? Have you had any marksmanship training? Do you use open sights, red dots, or scope? Examine all of these and then decide your best option for the money you have. I am happy with my Gammo's. Not their scopes (POS) LOL. I have a BSA red dot on the Varmint and Mach I. The Urban sports a Sun Optics 6-24 x 50 that set me back more than the cost of the rifle.
There is nothing wrong with the other brands whether German, Chinese, British, Swedish etc. Pick one based upon your shooting habits and pocketbook.
It is kind of like buying a sports car. Many models but no need to buy a Ferrari if you are never going to drive it over 45 mph.
I have enough cash to buy a Brocock,AirArms, AirForce, or one of the other Ferrari available but a MG works just fine for me.
Good Luck and welcome to the hobby.