J and J Dog Supplies: Leather Training Leashes
It's a clasp like the one on the leash on the web site. I've used these types of leashes for all my other dogs and have never had failures like this before.
The clasp isn't broken. It just somehow comes unclipped (opens) when walking the dogs (on pinch collars). Pinch collar ring isn't broken either.
OK, That's a piston or bolt snap. Those are usually pretty reliable but you can have a couple of things happen--I've seen the piston (the part that slides) get bent enough to make it not seat properly at the outboard end of the solid part of the snap and if it gets caught and twists on the collar ring it'll let the ring slide past the piston and you've got a loose dog. And is is possible (but not as likely) to catch the button that controls the piston on something and pull it open and free the dog. Check for a bent or loose piston and replace it if tweaked or discard the leash.
mmctaq put up an E-bay link for a "trigger" snap.
Just took a look at the type of clip you are talking about. Even though I love them and use them on all of my tracking leashes they are in many ways the least reliable type to use on a dog leash. The extension that allows you to open the clip easily is also easy to catch on things (the leash itself, and parts of a prong collar) and it doesn't take much pressure to open it and it'll just drop off of the collar ring.
No leash snap is totally fool proof but the piston style is generally more reliable than than the other clip (which is called a trigger snap in the marine field) which was pictured on the E-Bay site that mmctaq provided a link for.
Many of the snaps used on nylon leashes (and a few very cheap leather leashes) are chrome plated pot metal (a very weak zinc alloy) and will break easily--not at the mechanism but at the stationary part of the snap--the zinc alloy often has big "blow" holes in it and in my opinion are disasters waiting to happen when used on any dog who does any pulling at all.
Brass is preferable but isn't terribly strong either. Ideally, either stainless steel piston style snaps or bronze piston style snaps are the strongest but you probably would have to ask if the metal is brass or bronze and if the snap is silver because it's stainless steel or if it's only chrome plated pot metal. Brass snaps and bronze snaps also sometimes come chrome plated. Chrome plated steel (which is used to make both piston/bolt and trigger snaps) is very strong but will rust as the chrome plating wears.
By the way--when the trigger snaps are used on boats (marine applications) they are usually taped across the trigger so that it can't get caught on anything and accidentally open.
The recommendations on prong collars (even the Sprengers with the snap attachment) is to always use a second collar also connected to the same leash as the prongs themselves can and sometimes do come apart.
Inspecting the snaps on leashes should really be done periodically to look for tweaked pistons, trigger snaps that don't close all the way (occasionally happens) wear on the leather or stitching.
Do I remember to do this? Oh, hell no--I'm just as brain dead as the next person when it comes to preventative maintenance.