My S&W Model 64-3 has been a great gun these last few years that I've owned it. In that time I've fired close to 5,000 rounds through it without a hitch. Lately, though, it's been giving me, seemingly at random, a really heavy trigger pull once every 12-18 rounds of shooting. No, it doesn't have anything to do with overheating, as best I can tell, because it sometimes happens during dry-fire practice also. After getting through that one heavy pull, it goes back to its normal, smooth pull. I haven't narrowed it down to any one chamber it's happening with, and the ratchet doesn't appear to be worn, at least to my untrained eye.
Any ideas on troubleshooting this problem are appreciated. Thanks.