Just finished first build and took out to range. Bolt doesn't lock back after last round fired. I tried several new unopened pmags and all did the same. So assume its not the mags. Troubleshooting help...

what ammo are you shooting and whats your rifle setup? gas system, buffer weight, all that good stuff.

ammo or buffer/spring. tulammo is known weak.

A) Since you built the rifle; do you know how/did you properly lube the rifle for your range trip?














 

With an empty mag in, does it lock back if you pull the bolt back with the charging handle?

Did you check for gas leaking at the front sight block?
Your buffer may be too heavy.

What ammo you using?

Did you assemble the lower/upper yourself or was it bought already assembled? You may have used the wrong spring for your bolt catch causing it to bind up. I've seen people use the disconnecter spring by accident which will cause what your describing.

Clean and lubricate weapon.

1. Insert empty magazine, pull charging handle to rear..... does bolt stay locked back.

2. Load one round Mil Spec ammo, fire round...... does bolt lock back?

3. Put in carbine weight buffer, repeat (2)


Answers?

You don't by chance have a B.A.D. Lever  or similar type device attached to your bolt release?

The build is an Armalite upper with...
-JP Enterprises full mass BCG
-Rainier Arms UltraMatch 14.5" middy
-JP Enterprises silent captured spring
-Surefire muzzle brake
-Larue low profile gas block
-Larue Stealth 13.2" handguard
-Geissele SSF trigger
- Tactical Link BAD

This was the first time to the range and have never put a round through it. I applied FireClean to the internal components and ran it wet. The ammo not sure I grab 20rds out of a few K I had loose. This builds purpose is a duty car and want it to take anything I feed it. I did notice the hammer rubs against the bolt catch and binds the bolt catch up when disassembled from the upper. You have to push the hammer towards the cocking position just a tad to free the bolt catch but didn't think this would contribute to the issue considering the hammer is in the locked position during battery.

Also the BCG does lock back on an empty mag when charging. Tried firing one round 4 times and had the same outcome with no lock back.

Just try the simple setup on the bottom of the image, a standard buffer spring and a carbine weight buffer.

Sorry, double post.

This is more than likely your problem. Others have had the same issue, remove it and try again.

Remove the Tactical Link BAD and try again.

If the bolt catch detent spring is over pressure, it won't allow the catch to operate quick enough to catch bolt when firing. It will manually operated. I ran across this a while back with some lower kits I bought from some one I normally did not buy from. Not something you normally run into, so it can chase you around. Hope this helps.
Craig.

im assuming he means it's purpose is a "duty carbine"?

Check your bolt catch, spring and plunger.

Are you using Magpul 10 rounders?