I tried my coach's ammo that he loads to 1.125 and had the same issue. A few people have said to run my ammo down to 1.10, but to be honest if 1.155 works perfectly in all of my guns there's zero reason to adjust my press down for 1 gun that I'm not super sold on anyway. I did do a plunk test and it passed just fine. Bullet freely spun in the barrel. It does seem like some of the ammo is getting stuck on the landing part of the barrel. So eventhough the plunk is fine, the length may be getting it stuck on the land as the gun is working. Not really sure. I will reply once I get some free time to see if the 17lbs spring fixes it. I also have an 18lbs and 20lbs spring I can try, but I suspect 17 will work. If it doesn't then the ammo probably would have to go shorter.
One other note, I did run syntech through it as well which is flat nose whereas my loads are round nose. The syntech is obviously shorter than my ammo and still had the same issues.