I bought this Sig PM400 last October, it is registered a pistol but shoots like a rifle. No SBR's allowed here in Iowa so this was my best option. The funky looking "brace" works well when shouldered, it adjusts for length of pull and holds for over 200 rounds at a crack without readjusting so far. I'm nearing 1,000 rounds and no failures to report. I've run everything from Winchester 45 grain varmint loads to BH 77 grain match. The main diet has been XM855 from P-mags and the stock mag. It has exceeded my accuracy expectations to date. I have not scoped it but stuck with the factory irons and a cheap Bushnell TRS-25 red dot with riser. The target pictured was at 50 yards with the red dot in well under 30 seconds, just taking enough time to get on target and squeeze.
My wife gave me a flaming pig for Christmas but I think I'll save it for a future build, I don't want to mess with anything for fear I'll loose that 100% reliability!