Hello folks, I just want to relate to you a situation I had while trying out different bullet types of nearly the same weight in my 1966 model 99F in .243. I kept the powder charge the same (medium charge) and used bullets of similar weights to see if one was more consistent than the others in my rifle. After shooting a few different bullets with pretty good results, I thought I'd try the Barnes TSX for the first time. It was slightly lighter than the others but close to the same size due to not having any lead in its construction, as you know. My first shot sounded different than all the others of the day, but I thought it was normal for the bullet. Cycling the lever didn't seem much different, but it was slightly stiffer. My seconds shot made a loud concussion and gas went out around the bolt , but didn't hit me thank God. The casing was stuck in the breech causing the lever to be stuck also. I tried to cycle I with a bit of muscle and the ejector stripped past the rim and the casing stayed put. Then I noticed the primer (CCI LR) was pierced through, and that's where the gas came from. I had never seen such a difference in pressure from one bullet to another using the same powder and charge. I just tore down all the rest of the box and put the bullets back in the box. I did double check my charges and they were all right to the 10th of a grain. I was able to finally eject the casing by squeezing the ejector hard with my thumb as I worked the lever. It was stuck good. The casing showed signs of extreme pressure and it scared me to look at it. I just wanted to warn others about using the Barnes TSX or TTSX in their 99s. I can only figure that my bore is tight and the solids can't conform to the bore like lead based bullets. Just be careful!