No refunds does not equal no rights....
I am not a lawyer, this is not legal advice.
While the "no refunds or exchanges" policies are common in firearms sales, these policies can not be lawfully invoked when you were sold something that was misrepresented. The rifle is defective and therefore is not functional as advertised.
By cleaning it you have done what you need to ensure it can functional properly. Get a refund and/or file a dispute with the credit card company.
In Ontario, the Consumer Protection Act regulates this transaction. Here are some relevant parts:
PART III
UNFAIR PRACTICES
False, misleading or deceptive representation
14
.....(1) It is an unfair practice for a person to make a false, misleading or deceptive representation. 2002, c. 30, Sched. A, s. 14 (1).
.....Examples of false, misleading or deceptive representations
.....(2) Without limiting the generality of what constitutes a false, misleading or deceptive representation, the following are included as false, misleading or deceptive representations:
..........1. A representation that the goods or services have sponsorship, approval, performance characteristics, accessories, uses, ingredients, benefits or qualities they do not have.
..........3. A representation that the goods or services are of a particular standard, quality, grade, style or model, if they are not.
Unfair practices prohibited
17
.....(1) No person shall engage in an unfair practice. 2002, c. 30, Sched. A, s. 17 (1).
.....One act deemed practice
.....(2) A person who performs one act referred to in section 14, 15 or 16 shall be deemed to be engaging in an unfair practice. 2002, c. 30, Sched. A, s. 17 (2).
Rescinding agreement
18
.....(1) Any agreement, whether written, oral or implied, entered into by a consumer after or while a person has engaged in an unfair practice may be rescinded by the consumer and the consumer is entitled to any remedy that is available in law, including damages. 2002, c. 30, Sched. A, s. 18 (1).