I often got good groups from my 1943 Carl Gustaf, say around 3cm at 150 mt with metallic aims and my 63 years old eyes (no rest only a front sandbag). Yesterday suddenly I experienced a total inconsistency. Only element changed in reloading where bullets. Cause a shortage I had to buy Strela S&B Fmj 140 instead of Sierra match king (same grains). This rounds are about 2mm shorter than Sierra. Today I did rework loads starting from previous 42,2 gr of Vh N160 and ending at 43,7. With higher loads and a coal near to the sierra 78mm I had 4 rounds in the same hole and some closer spread. But I am still concerned about throat of rifle. Slugging the barrel I obtained .2657 dia but felt as all resistance was at the muzzle and way more space on the breech side. Any suggestion for checking deeper?