I had the same problem... took it to my gunsmith and he opened up the hole (s) in the gas collar and that fixed it.
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No tube.Did u switch the tube based on shell type
Cleaned it,found some high brass and buckshot and slugs problem solved.Shoots regular stuff now.New guns have sharp edges on moving parts and burs. It helps to clean, lubricate well and fire them. Once broken in, clean and lubricated try the low brass again. You will likely be pleasently surprised.