I had one and it worked, but that's not to say for an extended period. I did sell it after all. Doubt the next guy used it much. The ones pictured are probably the only ones made. The military takes a dim view of people cutting down rifles for entertainment's sake even in wartime. Mods are prohibited. Ask Peter... The ones that are sold today are re-engineered I'll bet. I've seen the short barrel, short gas model in my hands and it looked good. They must work or they wouldn't be able to sell them. Personally, I'd still rather the full length rifle. They worked fine.