Most of what you're going to find out there will be NLGI 2 and will work in most applications.
A number 1 will be too thin and a number 3, too thick, and anything beyond that just becomes more thick.
See this chart:
NLGI consistency number - Wikipedia
I looked it up, the Rocol product has clay as a thickener, old technology, but it is an NLGI 2, so look for that number with Molybdenum Sulfide added.
A grease that's suitable for water applications may be desirable, that's quite sticky and stays in place _ a synthetic grease is better because the oil in it won't break down like dino grease will.
What's in your gun now; specifically ?
The tech chart below of the Rocol product.
EDIT: stay away from Lithium products, they dry up after a while.