This morning I gave the JTS 43.06gr slugs a test. As you can see, my U2 700 .25 did not show signs of liking the JTS. The rifle's current tune had these 43.06gr slugs shooting at 951fps with an ES over 15-shots of less than 3fps. They shot very uniform velocity, but sadly the accuracy was not there.
The slugs were .252" at the base drive ring and were .247" at the forward drive ring. I tested dimensions all around the diameter of these cast slugs and they were spot-on uniform (very round). Really, they were as nice looking and uniform from one to the next as any swaged slug I have ever tried.
I could try adjusting the reg. and move the velocity around but I am not going to change it. From working with about 2-dozen various slugs through this rifle, past attempts at tuning any particular slug showed little change. In other words, if the accuracy was bad at a particular velocity, it didn't really change much with a velocity change. And of course, if you know anything about the Uragan 2 then you know that tuning is limited to regulator adjustment, suppressor on or off (harmonics) and trigger tuning, that's it. Messing with the hammer spring doesn't do much of anything with the balanced valve except cause premature failure of the poorly designed poppet assembly.

In fact, AGT tells you in the manual NOT to adjust the hammer spring! But we all know how us airgunners are about such warnings.
These JTS slugs group about as well as half of the various brands/weights of slugs I have tested. You can understand why prior to the trying the Altaros 49.5s I have been so frustrated with this rifle, not to even mention how many times the valve poppet/o-rings/stem have broken on this rifle.
Going forward, I finally have the valve poppet issue resolved and now with the accuracy the rifle is getting with the Altaros, I think I can finally find some happiness with the Uragan 2.
The JTS Dead Center 43.06gr Slugs were not favored by my U2 700 .25.