FTF and eject

[krallstar]

Bought a keyhole upper new, added a new Colt 20" govt profile barrel. Also added YHM freefloat tube. Also bought a Colt bolt carrier and colt bolt slightly used. Put new rings on it. Took it to the range today and was alittle displeased. Pull charging handle back let go and chamber a round. Pull trigger and round goes off. Bolt does not move. I tried a carrier and bolt from my Hbar and the carrier moved back about an inch then stops. I have checked everything i thought might be the problem. Plugged up what i can and used air. Everything seems good. One thing i noticed was the carrier i bought is a shrouded type. That's the one that did not move at all. My Hbar is unshrouded. I was using white box wwc ammo.

 

[atilla]

is everything lubricated in the upper?

have you tried a different buffer/spring?

 

[krallstar]

Everything is oiled. When using the charging handle all seems well. Smooth action no binding. Have not tried buffer or spring yet. The lower is from my hbar 20" Never had a problem with it. I also changed the stock over to an ace rifle stock. I was told the buffer and spring would work. Fixed it. Went over everything again and decided to change the sight tower. That solved my problem. The other block must have been blocking part of the gas port on the barrel. Went to the range this morning shot 30rds with out a hitch. Very happy now. This was my first time assembling a complete upper. I now want to build a middy length 16"

 

[op4guy]

First thing I always suspect with a problem like this is the gas key on the BCG or the gas tube itself. Short stroking is a common sign that it is not getting the pressure it needs to fully cycle. I would inspect the key to make sure it is actually tight and seated properly. After that look at the gas tube and make sure it is aligned correctly into the receiver and the FSB. I have seen pins come out of the FSB and rock the tube loose where it allows gas to escape freely and causes the short cycle.

I would not count out the buffer/spring but if you had it running on an H-bar with the same length bbl then it's highly doubtful that is the issue.