I went to my local Gun Dealer and purchased a buffer tube, buffer and buffer spring. I did most of my research before building my AR. Anyways, I asked if the buffer spring was suitable for a Carbine length rifle. They said, "yes it will fit". Didn't think nothing of it as I know they are way more knowledgeable than me. I installed buffer tube to the correct spec, castle nut to correct torque and staked it using a spring loaded center punch from Harbor Freight. I then tested to see if bolt locked back with empty magazine. Bolt didn't lock back. So I tried w/o magazine and tried to lock bolt back by pulling charging handle back and then engaging bolt catch but wasn't locking back. I sat there, being my first build ever I was nervous. I looked at it for minutes and and hours. Then I got an Ar15.com. Looked around to see if anyone had same issue. Some said Magpul magazines, bolt catch etc. So I then researched about the buffer spring. In my research I found out that there are different size buffers springs. Anyways, my buffer had 44 springs or twist or circles. According to what I read 44 twists/circles was for a rifle w/ longer barrel than a 16". And a carbine was around 40 to 38. So I decided to cut about 4 full circles from buffer spring. Now, buffer springs ain't that expensive which really didn't matter if I messed it up. But I did one by one, cut one off it left it 43, nothing bolt still not locking back, then 42, still nothing. I got to 40........ and wallah bolt locks back!!!! I noticed before this bolt was not going back far enough to catch on bolt catch. So the tension from the spring being soo long caused that to happen relieving tension by removing 4 springs or circles. Now my bolt locks back. Took it to the range to fire the first 300 rounds ran perfect and bolt locked every time after last round was fired. That was my solution. Try it if you have same issue.
Thanks again. Sorry for the long story did. It want to leave out much.