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So 2 points of concern, and my belief of why these are generally not hitting their target strength. 1. After the rope is spliced through the other side, it is then bent back 180 degrees on itself for the bury. Theoretically this gives you a 1:1 bend rad, which Dyneema states is the min. to retain full strength, but realistically i don't believe it does. In all the illustrations i have seen in reference to the min. 1:1 bend radius, plus the verbiage used, the radius the rope is bent around is a rigid material, i.e. a steel shackle or pole, dyneema of course being quite a flexible and soft material can be scrunched up into a less than 1:1 ratio when another rope is constricted around it. So right there, is real loss of strength.

2. There is also the "throat angle" which is the measured distance from where the inside of the rope eye makes contact with what it's pulling against (in this case, the other end of the rope being spliced through and folded back on itself and then buried, the other eye, this loop is literally just two eye loops pulling against each other). Throat angles for dyneema are suppose to be a min of 3:1 and preferred 5:1 to retain max strength. This creates much less than 1:1.

This is why i think you are getting less actual strength than what Animated Knots states. I'd bet they are getting the theoretical strength using roughly the same equation as a soft shackle, which is a bad idea since the eye of a soft shackle once pulled over the knot is probably pretty damn close to 3:1 throat angle.

Now all of this is not to say a Grog Sling is a bad idea, you have to choose a rope thickness that will ultimately yield the safety margin needed for your application, so they can of course be super good enough. From a purist standpoint, bending the rope back on itself like it is here is scary af to me.

Short bury, recommended bury, long bury... but no dingleberry.

the sliding on the shackle is likely causing a local weak point from melting or abrasion.

Thank you Jake you're quite a mastermind, explained everything perfectly.  I hope to see more of you on this channel

The "finger trap" quality of hollow braid Dynema is contingent on it being able to contract around the cordage inside if it. With the tails crossing, you have the Dynema trying to construct around a bulge. The only friction would be where the tails cross. Long but separate tails would provide the most friction.

1:12 I feel like Ryan jinxx it's warm, got me😭😭

I wonder if Animated Knots has a test facility, or they just regurgitate "known knowledge".

Here's another method for making a dyneema loop that does not require the 180° bends for burying the ends that this method does:  https://www.youtube.com/watch?v=9-4AYV7jKRA

I wonder if the loop sliding along the bolt towards one side has an effect? Could it be getting pinched in the gap between the bolt and shackle hole? You might consider using a spool to keep the loop in a more friendly position.

I guess prudence dictates that this loop should be treated as 100% breaking strength?
Still not bad considering the strength to bulk/weight ratio.

I noticed you used very shot tapers. My experience with Polyester and Dyneema tells me to use at least 1-1.5 fid length tapers or longer.  I wonder if testing different taper lengths would have any effect. Given you failures were not consistently at the splice.

Could this splice be used to create new slings on cams?

One thing I noticed, is that after the splice there is a really sharp turn, as from how it looks the end is buried on itself. Could it perhaps be a bit stronger if it were to be buried on the "other" strand? That might be one to test in the future. Obviously the caveat here would be that perhaps it would also be a lot weaker as the overall friction of the splice and fingerlock could also be less due to a more straight routing.

maybe the reason they break more easily when you shock load them is that you pull on the tighter strands first and break them.  it might just happen too fast for the slack to come out of all of the strands.

Would love to see the double wrapped grog tested here if it hasn't been already.

This seems like it might be a way to replace old cam webbing……no ?

If you really want to feel like Ryan you gotta say it kilonewtents.

Have you ever tested the finish of the shackle?  The zinc plated finish is rough, try polished steel after removing the zinc by soaking in vinegar.

Watched so many of these break tests that the sound of the hydrologic is my tell to strength or weakness.

Love the work you do, thank you!!