I believe that the people operating Mcgowen in Kalispell, MT have nothing to do with the original in St Anne, IL. The son of the original owner was nothing compared to the father. I mean in quality of product and customer service.
I have had issues with Lilgun and the 350. The Hornady manual max is way to hot for my rifle. I ended 3-4 gr under max. Lilgun is very touchy. I use SW SBR Socom powder for it, I get 2300 out of a 21" barrel shooting the 170 gr Hornady bullet in Starline brass. I saw the powder use on...
90+% isopropyl alcohol on patches until clean. Use ISO HEAT to save money. Then a bore brush with Hoppes to get into the nooks and crannies. Finally a patch to check for cleanliness and some oil for rust prevention,
MGM barrels had a video out and they mentioned frame stretching with certain cartridges. Remember recoil is not the same as pressure. Sure a 12 ga turkey load kicks the snot out of you, but it is because of the large payload not the chamber pressure which would "stretch" a frame.
I have several. They are handy and accurate. My officer model has dropped the most deer of all my MZs. I converted it to a closed breech for BH209. 75gW and 250 TMZ Yellow crush rib sabot. Even crappy ones sell for big money on GB.