freshly assembled ar won't cycle

[blysccr]

it's not the magazine, used various mags in other ar's and it worked.

the bcg wont eject the spent round which obviously won't chamber another round.

this happens when a mag is inserted and when a mag isn't inserted.

i can pus the buffer and buffer spring down no problem.

i'm a super noob, where would the best place be to start looking for the culprit?

thanks

[.45Kimber1911]

Blocked gas tube. Remove it and look at the hole on the bottom. Try blowing some gun cleaner down it slowly while it is still in the upper before you remove it. It should trickle out the end of the muzzle. If not, there is a blockage. Fair warning, gas tubes are hard to get right now for some reason. You might want to try to clean it first before trying to search for a new one.

[JayBell]

it's not the magazine, used various mags in other ar's and it worked.

the bcg wont eject the spent round which obviously won't chamber another round.

this happens when a mag is inserted and when a mag isn't inserted.

i can pus the buffer and buffer spring down no problem.

i'm a super noob, where would the best place be to start looking for the culprit?

thanks

you need to supply more info.

barrel length/type/composition/maker?
BCG make?
is the gas key staked properly?
Gas system length?
is the tube upside down?
Ammunition type and maker?

did you assemble the upper yourself?

info, we need it to diagnose.

[DennisH82]

Most likely this isn't the issue but have your checked your gas rings on your bolt? are their any missing? should be three and they should all be offset (Not lined up with each other) That was an issue I had with my goverment issue AR's over the years.

[bac0nfat]

Try to be more specific about the failure...

You say that the BCG doesn't "eject," but does it extract the round?

In other words, when you fire the gun, does the bolt carrier move at all, or does it stay completely closed?

Or does the bolt carrier move rearward but leave the empty cartridge in the chamber?

Or does the bolt carrier move rearward and pull out the empty cartridge, but fail to eject it through the ejection port?

Or something else?

[.45Kimber1911]

It is obvious that it is a problem with either the gas system or direct impingement system depending on what type of AR set up you are trying to run.

Check your gas system all the way from the bolt to the gas block. I missed that this was a fresh "build". Make sure you have all the parts in there that are supposed to be there first off. Then look to make sure your gas rings notches are not all lined up and are staggered. Make sure you have the right kind of bolt for your system. A DI bolt is going to be different from a gas system.

Make sure your gas tube is the correct length for your gun. Blow some compressed air through it and listen for it to come out in the barrel. There is a small hole in the top of the barrel that needs to be lined up with the gas block. If you are running one of those low profile gas blocks, make sure that it did not get bumped out of place.

I don't know much about DI systems, so if you are running one of those, you better ask someone else for advice with those.

[bac0nfat]

It is obvious that it is a problem with either the gas system or direct impingement system depending on what type of AR set up you are trying to run.

Check your gas system all the way from the bolt to the gas block. I missed that this was a fresh "build". Make sure you have all the parts in there that are supposed to be there first off. Then look to make sure your gas rings notches are not all lined up and are staggered. Make sure you have the right kind of bolt for your system. A DI bolt is going to be different from a gas system.

Make sure your gas tube is the correct length for your gun. Blow some compressed air through it and listen for it to come out in the barrel. There is a small hole in the top of the barrel that needs to be lined up with the gas block. If you are running one of those low profile gas blocks, make sure that it did not get bumped out of place.

I don't know much about DI systems, so if you are running one of those, you better ask someone else for advice with those.

If I'm not mistaken DI (direct impingement) is the standard gas system in an AR. Perhaps you are confusing DI with piston?

[.45Kimber1911]

If I'm not mistaken DI (direct impingement) is the standard gas system in an AR. Perhaps you are confusing DI with piston?

Yup....Been a long day without any coffee.

[39flathead]

As eluded to many times above, check your gas block.

I recently bought a used upper from someone and even though he claimed it fired without a hitch, the gas block was hitting the free float tube not allowing it to allow all the gas to get into the tube.
I installed a low pro block and new tube and it runs fine now.

Be sure your block is going to the "step" on your barrel if it has one and make sure you have the correct diameter block for your barrel.

[unclejumbo]

I checked my new build for gas flow by putting a bit of fish tank aerator tubing on the bolt end of the tube and blowing into it. It's an easy way to tell if the gas is flowing. You can also move the gas block around (assuming it's not pinned) while blowing in the tube until you achieve optimal air flow.