Jeff- I've fired the rocky mtn snypers (same design IMO) into 6 animals, and the only one that WASNT a passthrew was a deer I hit in the spine.

2 antelope, 35 & 42 yrds, both passthrews
4 deer, 8 to 30 yrds 3 passthrews, one spine...

It really clould be shot location (especially if you hit the offside shoulder), the only deer I hit in the shoulder (muzzy head) I didnt get a passthrew...

also, why does it matter so much? Just outta curiosity what is your the ratio of passthrew to not?