So I brought Emma 2.0 to the range today for the first time. We had a few mishaps along the way sighting her in, but she seems to function well with one exception: After the last cartridge is fired the bolt is not locking back in the open position. This happened with almost all mags fired today, except the last. I would have tried another mag, but I was out of ammo. Is there a break in period for a bolt catch? I'm not sure why this is happening.

Does ur bho move freely? You have another bolt to try? Steel nags? Pmags?

What brand rifle and Bolt Carrier?

 

Failing to lock back on an empty mag is generally a gas problem. Check your bolt carrier, the gas key on top is likely loose. If so it needs to be tightened and properly staked. If that doesn't fix it, you may need to see an Armorer or get a new bolt carrier.

 

There should be no break in period on an AR.

What brand rifle and Bolt Carrier?

 

Sounds like a gas problem. Check your bolt carrier, the gas key on top is likely loose. If so it needs to be tightened and properly staked. If that doesn't fix it, you may need to see an Armorer or get a new bolt carrier.

 

There should be no break in period on an AR.

 

And do you have tomorrow's Lotto numbers too....

Specs on the AR and BCG please. Did you buy it complete or piece it together yourself? Did you clean the chamber well and strip, clean and lubricate the BCG thoroughly? What kind of ammo were you shooting?

Specs are here: http://njgunforums.com/forum/index.php/topic/10555-ar-pics-lets-seeum/page__view__findpost__p__708281

 

If I pull back the charging handle with an empty mag in it locks. Using a Pmag. Only had one with me so I dunno if it's the mag? I pieced it together. The rifle had never been shot so I only lubed it thoroughly with Remoil on the BCG and Slip 2000 EWL on charging handle. I was using Cor Bon 55 gr .223 match performance ammo, Herter's, and Wolf. Mostly Cor Bon though.

Take off your BAD lever and try it again.

Why are you using different lubes on different parts? Throw the Remoil away and just use the Slip.

 

It may be the BAD lever, especially if your bolt catch is a little out of spec.

 

A Windham Weaponry BCG? Yeah, definitely make sure you check the carrier key. See if it wiggles in place or you can tighten the hex bolts. My money is on this.

Did you clean the chamber and lugs well with a chamber brush to remove the grease that's used for storing? If you have grease inthat area, the bolt might have a hard time turning pulling out as the BC is being cycled back. What HK said makes sense, I have heard some people have issues with the added weith of the BAD lever preventing the bolt catch from engaging. I have BAD lever on two of my ARs, never had that issue but worth checking as a form of troubleshooting. Make sure the bolt catch moves freely and maybe add a drop of oil on it. I think may be dealin with a combination of the BCG not being broken in yet and using weak ammo (Herters/Wolf). Clean and lube the BCG and hand cycle the AR a number of times. More importantly, I would use some quality 556 brass cased ammo to break n the weapon for maybe 100 rounds or so then try the steel cased 223 ammo.

 

The last new PSA upper I broke in with a new DPMS BCG I ran 40 rounds of PMC bronze 556 without issue. I switched to a box of Herters and had some FTF's and the bolt wouldn't hold back on the last round. It was obvious tha the BCG wasn't traveling far back enough. Switched back to PMC Bronze for the 60-80 rounds. Took out the BCG, wiped it down a little relubed it a little and continued running Herters until I ran out of ammo on the 140 round mark without issue.

Forgot to mention, if the BAD lever is not the problem you might wanna toss in a heavier buffer in there to slow down the BCG. Without physically being there it is hard to tell if it is over gassed or not.

Yes, make sure you have a proper weight buffer for your specific gas system and barrel length.

 

How was ejection in terms of distance and direction?

Not locking back on an empty mag is a symptom of an under gassed system, not over gassed.

Not locking back on an empty mag is a symptom of an under gassed system, not over gassed.

 

Over-gassed is more common than under-gassed. And over-gassing can cause over running of the follower.

Yes, over gassed is more common because lower tier guns generally have larger gas ports to get the guns to run properly on shitty ammo. It also helps when you don't build your BCGs to spec and lose gas around the carrier key because you cut corners and don't follow the TDP by shot peening, MPI, torquing and staking the carrier key bolts. The extra gas lets the gun "fake it" for a while and appear to run properly.

 

They typical symptoms of an undergassed gun are:

1)It won't strip a new round from a mag

2) It won't lock back on an empty mag

 

Every time I have seen these issues crop up (always in a Bushmaster or Rock River or Olympic Arms or Windham Weaponry etc...) it was a bad carrier/loose carrier key - except once, where it was a bad cam pin that was putting some drag on the bolt an slowing it down enough where the BCG couldn't strip the next round from the mag. A new cam pin solved the problem.

 

That being said, the test for an undergassed system is:

Load one round and insert empty mag. Fire and see if it locks back. If it doesn't = under gassed is first place to look.

 

Check BCG first - replace worn rings and check carrier for loose carrier/gas key. (A loose carrier key is the most common reason for being under-gassed in guns using non-mil spec BCGs)

 

Check gas tube next. Make sure that here are no leaks in the systemn no pinholes, the tube isn't bent where it meets the carrier key, and there is no seepage around the FSB or the receiver where has tube passes through.

 

Next, make sure the FSB is straingt and tight and the taper pins are in place.

 

If possible, check the gas port to make sure it is not obstructed with debris (part of a patch, dirt, carbon, etc...)

Gas system is a mid-length. The hex bolts look like someone took a punch to the metal next to it, creating a lip that goes over the hex bolt. There are 2 punch marks per hex bolt. I have a standard rifle length spring and buffer. I will take apart the bolt and check it.

Yeah, the key is supposed to be staked in.

gas leak, undergassed or buffer too heavy.

 

either way, the bolt is not moving back far enought to lock.

 

maybe try true 5.56 ammo.

Chris, have you shot this again? Any updates on the issue?

maybe try true 5.56 ammo.

 

This^. That particular CorBon ammo is a bit underpowered. In a broken in gun it would probably be fine. In a tight new gun possibly not.  Try some M193 or M855 spec ammo and see if that helps. Also, clean and lubricate the rifle thoroughly before your next range trip.

http://njgunforums.com/forum/index.php/topic/55934-ftf-on-steel-ammo/#entry717130