Any scope that can go on a .22 rim fire will be safe for a gas ram! It is only a small kick straight back at you after all! I have never found the recoil on gas rams to be that bad, now had a Hatsan 60S TG GR, Theoben Sirocco (low pressure) and now got a Theoben Fenman HE!
Never had a problem with mounts coming lose or scopes dying on them!
"corners should be round" Theo Evo .22/.177 - Meopta 6x42, DS huntsman classic .20 vortex razor LH 3-15x42 under supervised boingrati tuning by Tony L & Tinbum, HW77 forest green - Nikon prostaff 2-7x32 plex.
Not necessarily, those Siroccos were also available as FAC if I remember correctly, I have certainly seen some Theoben gas ram guns advertised as FAC. They would not bother having different seals et al required for various power levels, this is Theoben we are talking about!
The only difference was the pressure the rams ran at! My Sirocco I over gassed when I got it and it was happily thudding along at 18ft lb until I bled some air out of the Schrader valve and dropped it to 10.4 ft lb where it was as meek as a very mild thing!
Had my share of GR rifles over the years, can't say I've ever had a "scope killer" even 177 fenman which was probably the worse rifle for recoil I've experienced