So, what exactly is an improved cylinder? What makes it improved? Can I shoot slugs out of imp. cylinder?
In non-technical terms it is a very small amount of choke. It gives a slight increase in pattern density at longer ranges. You can shoot slugs out of it.
It is about .007-.010 constriction.
Standard chokes are as follows
.007-.010 Improved cylinder
.012-.014 light modified
.022-.025 improved modified
.035-.040 extra full
These figures are subject to dabate but they are the numbers I use to alter constriction or plan a pattern.
Your cylinder is safe with slugs.