I just completed a 24” 6.5 creedmoor build. After getting everything needed putting the barrel, gas block and tube, upper and rail together, I checked how the BCG and charging handle worked. The bolt head of the BCG I purchased would not go into the star chamber of the barrel. Being a novice, I went to a Gun smith for answers. He took one of his BCGs and tried it and it worked. He told me the BCG he used was of better quality than the one I’d purchased. I bought that BCG and it’s been fine. When I finished the lower receiver, I put it all together and did a snap cap function test. It did very well. I did it a few times with no problems. Once done, I decided to check headspace. I took the bolt out of the BCG, removed the cotter pin took out the firing pin and cam. I then took out the extractor and the injector. I then replaced the cam and the firing pin into the the bolt and put it back into the BCG and proceeded with the go/no go test. I inserted the 6.5 creedmoor go gauge into the barrel and slowly slid the BCG into the barrel and it won’t pass go. Someone please advise. Thank you.