Spliceing 12 srand / single braid

[Brion Toss]

Hello,
First, I am assuming you are using a Spectra snare. If so, try making a round turn with it around the very tip of the line, instead of just looping it onto the line.
Next, how far down the standing part are you entering the Wand? The further down you go, the harder it is to bury, and thus the easier to pull the snare out. I've found that 2 to 2 1/2 tracer lengths more than the length of the tail is fine.
Next, what taper are you using? the longer and fairer the taper, the easier the bury.
I generally lay out only 6 strands before burying, as this leaves the tail more coherent; the remaining strands don't tend to distort and hang up. Again, less tucking effort. After the bury, I pull the tail out a bit, and cut off the last two to finish the taper, and then cut the remaining 4 at an angle.
One other possibility is that you are snagging some standing part yarns. If you are, they'll deform as you try to pull the tail past them.
Single-braids that are meant for this kind of splice are structurally the easiest to splice, but they also require the greatest fussiness in measuring, tapering, and entering.
Fair leads,
Brion Toss