won't stay closed
 

My SBT opens up when fired it locks up tight with no play but opens up when shot??

Parker SBT SC grade

It is usually a bolt bite issue. Or a weak/broken top lever spring. But usually the bolt.

thanks I'll contact previous owner and find out as much as I can about previous work etc

forgot to ask what is the bolt bite

My SC does that on occasion with 3 dram 1 1/8 oz loads. My shoulder can’t stand a steady diet of 3 dram shells so I am delaying getting it fixed. I load very light 3/4 or 7/8 oz. Loads and never have an issue. Score is not a big issue with me but comfort and pain is.

I assume an SBT "wear plate" is something along the same lines as the locking plate in something like a 101, Citori etc. and not shaped like the locking block in my Perazzi's?

Parker bolting from a 1930 catalog.

Attachment 123736

The fit of the replaceable "bolt plate" is critical as well as the strength of the top-lever spring.