Sorry to hear of your experience. This has not been the case with my Thompson Center Black Diamond XR. It loads great and shoots even better.

For one thing the rifle is new, but that really should not make a difference in they way it loads. One thing I know is silly to ask but, are you using a short starter to get the sabot past the muzzle into the barrel? The reason I ask is on a different board another poster was telling of the same problem and finally when I asked the to describe their loading procedure, they did not use a short starter. They thought that you could set the projectile with just a ramrod. We all know that does not work. So that's why I asked.

Some things I would try is

changing sabots. In the new Thompson Center projectiles I heard they changed from the old sabot to a different one. Whether this new one is thicker I do not know. Perhaps a different sabot might give you that second shot without the swab. You might want to give a Knight Sabot a try. They load great in all my rifles.

I have found that the 375 grain Buffalo Bullet SSB sabot (Cabela's sells them) shoot great and load great out of my Black Diamond XR. This might not solve your problem if you have trouble loading Shockwaves because those also load great in my rifle. I could understand if instead of Shockwaves you had bought Hornady SST (same bullet) and was loading a Harvester Sabot with them. I broke a short starter trying to load them in my Diamond. The shockwaves on the other hand load stiff, but beautiful. I also have good luck with the 240 grain T/C Mag Express XTP and 100 grains of Goex FFFg powder.

Another projectile you might want to use is 460 grain No Excuses Conicals. They are .503 diameter. And they shoot excellent with 85 grains of Triple Se7en powder and they load like a dream. Anything they hit will go down. I have shot five of them in a row without swabbing.

If trying different projectiles does not help, then after season I would send the rifle back to Thompson Center and have them figure out what the problem is. You have one of the best rifles on the market. I think it rates #1 in customer satisfaction (all but you of course).

Congratulations on the first buck, shame about the second one.