Tight bore barrel

Shopping for a 650mm tightbore for my M14 since Knucklehead is about ready with the new outer. This one any good, or does anyone have a specific brand they recommend?

http://www.airsoftpost.com/product_info.php?cPath=24_72_375&products_id=24376

I would trust Prometheus, Systema, Guarder and KM Head-1950

All the ones by those 4 say they're for the PSG-1 does that mean it wont fit into the m14?

Well, you are still going to have to do some modifications. What you are going to have to do is have knuckle had look at the stock barrel and get where he's going to have to go over it either with a surface sander or a milling machine with a in-mill bit at the correct size.