Barnes has continued to change their bullets since the original X bullet came out. This is for good reason.
Every bullet manufacturer, Every Rifle manufacturer, Every car manufacturer, etc etc........
Continues to offer new products and developments,
It's called increased revenue and growth.
Business 101.
Or it's called fixing bugs. No one can objectively say the first three generations of Barnes monos have issues.
I shot a bunch of original Barnes X bullets and found expansion to be inconsistent, even at 7mm RM velocities. I quit using them as a result. TSX were very accurate in every rifle I tried them in but I decided not to use them on game so have no experience there. Have been using the tipped X bullets (MRX, TTSX and LRX) since they first came out and have been impressed with the wound channels.
I really wanted the first generation Barnes X bullets to work, but they didn't work reliably. I dropped a coyote at 75 yards or so with no visible entrance or exit wound. Another had a softball sized hole. One antelope took three shots total with a 160g X bullet. It laid down after the first two but kept its head up as if sunning itself. We circled around and the third round, from another angle, took part of the heart and put the unfortunate animal out of its misery. For me, that kind of performance indicated a definite "problem" with the X bullet design.
The third generation MRX and fourth generation TTSX and LRX have worked reliably, no problems encountered - no signs of failure to expand in over 14 years of use by my hunt group, coyotes and antelope to elk
How many instances of poor expansion did you experience? I would be interested to hear about them, if you're willing.
I also used a lot of original X bullets, and never experienced anything like that, though I am aware that there are many people who did experience sub-par performance with that bullet. I did shoot a Pronghorn with a 160gr X from the 7RM, just as you did, on a hard-quartering shot. The bullet entered the onside shoulder/brisket intersection and exited the offside near the tail. The buck had the same reaction as yours did, dropping to the ground but keeping its head up. Another shot to the neck ended it. When I opened the pronghorn up, however, I found that the quartering bullet had expanded and done plenty of damage. The old buck was just a little tougher than most, I guess.
Again, it's totally normal for companies to make adjustments to existing designs and manufacturing processes to try to improve performance. The PT has undergone different methods of making the jackets, different longitudinal placement of the partition, different jacket thickness profiles, different lead alloys (IIRC), etc, to try to optimize performance. This is a good thing. The original X bullet, like the original PT, the original automobile, and even the original toothbrush, was a good albeit imperfect design. Subsequent modifications after inception have improved performance in all of these cases.
