Johnny, a little hard to follow. Is the picture below the same as what you are describing?

Or is it like this one? I just tied both of these and this knot seems to come out more like yours. 

 But I have seen hooks with really sharp edges when the eye of the hook is finished (or more correctly unfinished ) Meant to add that an offset eye is much better than a straight one 

Thanks lads. I tie it with the tag end looping over and worry about the stress on the knot. Those diagrams make the under tag end look fairly simple... until I try it

 def worth a try. looks to be a better one with the straight eye

 With an offset eye hook, the first pinches the tag end and can lead to earlier failure imo

Straight eyes. ( not offset eye).Always go in from front .when you pull ( not strike) it rolls correct way. Hold hook in hand try it . makes sence ,Beak hooks from back.( strikeing)

 Johnny  I got to second step no problems  but third step completely lost lol

:). I can do it with eyes closed. But can't explain. Lol dumb ass.

 Well I'll be!

That actually worked, and is easy to do! Looks a lot better than my version.

Who knew that there were so many ways to do a snell knot? Now I'll have to redo the 7 rigs I did last night ha ha.

I went fishing yesterday with a rig that used 100 lb braid, with my own unscientific teeth tests I found that 100 lb braid is impossible to bite through, while 60 lb mono is possible. However the braid is quite visible in the water.

Thanks so much Little Johnny, I really appreciate it!

Exactly as it should be ! 

 Hmmmmmmm....

I tried a rig with that setup at lunchtime today, got hit by something big, and guess what?  Got bitten off again!!!

That was with 100 lb Black Magic tough trace, the knot suggested above, top hook (where it broke) was a Mustad 4/0 Octopus circle.  Drag wouldn't have been more than 5 kg, I could pull it out by hand.  The line where it broke had a lengthwise cut on it, possibly caused by where the hook eye joins onto itself?  This is different to the other failures, the line previously was obviously breaking at the hook-most portion of the knot, whereas I'm not entirely sure where it broke this time.

This is getting pretty old.  What's left to try?  Wire trace?  Different hooks?

 i am amazed by this , any of the options in decent leader would not be snapping? you must be getting bitten off by something? got me stumped unless your using 20lb leader?

I would seriously doubt the knot would be that neat on a 4/0 hook.....I think the leader is much lighter than you believe 

It's possibly the hook that caused the leader to fail this time.

Ive used the black magic leader in 40lb and broke off in random places mid fight,I dont use it anymore

:). 130 lb black magic. Never lets go unless shark gets it.

You might be getting busted off on a sharp ledge?     Ive flung salmon up the rocks like a poled tuna with 100lb leader.  I dont think its the line....youll have to tell me where your spot is for better info....wink wink.

 I have done lots of tests on this, and after looking closely at lots of hooks and the line after tying a hook on, it's almost certainly the hook.

As others have said, some hooks have a sharp edge in the gap where the end of the hook loops back on itself.  I didn't think that the gap was that bad, but it's obviously cutting a slice into the line (observed after tying a knot and looking closely at the line).  

It turns out that the Mustad hooks I was using cause this nick, while Gamakatsu 6/0 circles don't cause a nick. 

So the moral of the story is: don't use snells on larger Mustad Octopus Circle hooks.

No dramas. Secret is do Knott tighten knott. Last thing is poke through eye.

 I have been experincing the exact same issue of the snell breaking at the eye with minimal pressure. I use a knotless snell on 5/0 gamakatsu octopus hooks using 40lb black magic trace and never seem to have an issue in the past.

It seems the sharp edge in the gap where the end of the hook loops back on itself is the issue and no matter what snell you use it will breaked in this location. 

Curious to see if anyone else has experienced this type of failure and what you have done to mitigate?

 Little Jonny I have been tying that way since my granfather taught me knee high to a grass hopper and never found a better knot yet. 

Agree need to tie the knot first.... pull up tight... then poke through the eye. But only with an offset eye, don't worry about it with a straight one. Never have them fail at the hook eye and use all sorts of brands and sizes. 

Through first pro in rocko . Bronzed hooks , no eyes . Just flattened eye . It grips to anything. I’ve had a couple where they have snapped top rig . But it’s always been on big double headers . I put it down to fish fighting against other fish . Have come across burs also . I use tiny file . Most of time bur on inside of eye