I've been going in circles trying to peg down Charles the younger, but it seems he does exist.
In the newspaper, the Birmingham Daily Post 02 February 1877 there is a list of patents, one being for Charles Pryse, the younger, who had applied for a patent for improvements for revolving and repeating small arms. Patent dated November 15, 1876.
Sometime after 1888 (can't find the reference in my messy notes!) there is a clerk running an ad seeking employment, as his prior employer, Charles Pryse (gun manufacturer) had retired in 1888. That makes me think Charles the younger wasn't all that much younger, in comparison to Charles the elder.
Could he be a cousin, and the terms elder and younger, were not meaning Senior/Junior, but just to keep it clear which Charles was being referred to?
Could he have been a son of Charles the Elder's brother John? I read the articles on John's murder, and it indicated he had children.