Help the BCG locks after last shot but bolt not retracting

charliebrown1999

Sergeant of the Hide
Full Member
Minuteman
Jul 25, 2018
251
47
At the indoor gun range this morning I fired 10rds from my Aero PRecision AR15 and after the last shot the BCG locked back but the bolt did not retract. This prevents me loading a full magazine. This is a new development on the new AR15 which has only been shot a total of 70rds. I used same ammo PMC 223A as before when there were no problems. I have been lubing both my AR15's with Mobil 1. The PSA AR15 has a PSA BCG and runs perfectly with this lube. The Aero Precision, with an expensive Tool Craft Nickle boron bolt and BCG, is the one giving me the problem. Perhaps I did not give the BCG enough lube. I need a little advise have from the cognoscente.
 
The problem is you went to a range (I hate ranges, especially indoor ones).

Unsolicited opinions aside, take your bcg apart, check for anything unusual/anomalous, clean thoroughly then reinstall with lube per your normal procedures. Shoot it again and see what happens. Otherwise swap your other AR’s bcg and see if it happens with that one.
 
FWIW, PMC Bronze is pretty weakly loaded .223 ammo.
Myself, I wouldn't use it for breaking in an AR-15... it is that weak.

I'd Try some 5.56 for break in for about a 100rds, then try the PMC again.

And the question about the buffer and recoil spring is also pertinent.
 
  • Like
Reactions: msgriff
tool craft BCGs aren't great, and NiB is one of the worse coating applied to bold carriers.
I'd try the PSA bolt in the faulty rifle. I would also do a gas ring test on the TC BCG, as well as inspect the gas key, gas tube, and gas block.
Also make sure you are using the the correct buffer spring and buffer
 
At the indoor gun range this morning I fired 10rds from my Aero PRecision AR15 and after the last shot the BCG locked back but the bolt did not retract. This prevents me loading a full magazine. This is a new development on the new AR15 which has only been shot a total of 70rds. I used same ammo PMC 223A as before when there were no problems. I have been lubing both my AR15's with Mobil 1. The PSA AR15 has a PSA BCG and runs perfectly with this lube. The Aero Precision, with an expensive Tool Craft Nickle boron bolt and BCG, is the one giving me the problem. Perhaps I did not give the BCG enough lube. I need a little advise have from the cognoscente.

I'm having trouble imagining what's wrong. The BCG locked back as in, the bolt catch held the BCG to rear? The bolt should be in the extended position (cam pin forward) when the bolt has unlocked and the BCG is traveling rearwards.

1640048350333.png


The bolt is in the compressed position with cam pin in the rear position when the bolt has locked into the barrel extension
1640048335753.png
 
"Did it lock back on the carrier and not the bolt?"

"yes"

There's your problem. The BCG should travel far enough to the rear for the bolt catch to catch the BOLT, not the carrier. Also, it SHOULD be impossible for the bolt to retract into the carrier unless the BCG is in the forward position, so there's nothing wrong with the BCG.

Your problem will be not enough gas for some reason, very likely the weak PMC ammo mentioned previously.
Also mentioned previously--you need to make sure the BCG is mechanically CAPABLE of retracting fully to the rear enough to lock on the BOLT, not the carrier. This is easy-insert an empty mag and pull the charging handle as far as you can until it stops. It should lock back on the bolt. If it will not do this, you have other mechanical problems like the wrong spring/buffer combination etc.

If it WILL lock back when operated manually, then the gas system may be at fault. But the first thing to do is try different ammo. Also, the BCG needs to be kept wet with oil during breakin, especially inside where the gas rings are. A couple drops in the exhaust holes on the carrier periodically will do.
 
tool craft BCGs aren't great, and NiB is one of the worse coating applied to bold carriers.
I'd try the PSA bolt in the faulty rifle. I would also do a gas ring test on the TC BCG, as well as inspect the gas key, gas tube, and gas block.
Also make sure you are using the the correct buffer spring and buffer

Please enlighten us on why Toolcraft bcg aren't great??? I can't wait to hear this

Toolcraft has a .gov contract making bcg for the .mil and you may not know they also make something like 9000 BCG a week for lots of OEM AR manufacturers and companies selling rebranded BCG's...

I've built 40-50 AR's with Toolcraft BCG's without a single problem and 10's of thousands of rounds fired.

I'm not a NiB fan but their DLC carriers are slick as snot.


 
Last edited:
Please enlighten us on why Toolcraft bcg aren't great??? I can't wait to hear this

Toolcraft has a .gov contract making bcg for the .mil and you may not know they also make something like 9000 BCG a week for lots of OEM AR manufacturers and companies selling rebranded BCG's...

I've built 40-50 AR's with Toolcraft BCG's without a single problem and 10's of thousands of rounds fired.


THIS^^^^
 
  • Like
Reactions: Ravenworks
tool craft BCGs aren't great, and NiB is one of the worse coating applied to bold carriers.
I'd try the PSA bolt in the faulty rifle. I would also do a gas ring test on the TC BCG, as well as inspect the gas key, gas tube, and gas block.
Also make sure you are using the the correct buffer spring and buffer


Wow I can see you've been around and know a thing or two about AR's.
Let me know about Toolcraft after you grasp a better understanding.
 
  • Like
  • Haha
Reactions: rpoL98 and mtrmn
Please enlighten us on why Toolcraft bcg aren't great??? I can't wait to hear this

Toolcraft has a .gov contract making bcg for the .mil and you may not know they also make something like 9000 BCG a week for lots of OEM AR manufacturers and companies selling rebranded BCG's...

I've built 40-50 AR's with Toolcraft BCG's without a single problem and 10's of thousands of rounds fired.

I'm not a NiB fan but their DLC carriers are slick as snot.


first of all, being chosen by the military for use doesn't mean much, it just means they were the lowest bidder who produced a product with good enough quality and availability.

There are several reasons why I don't like tool craft bolt carriers.
First, tool craft doesn't manufacture bolts, they only make bolt carriers. They source third party bolts, and will not disclose their source. Given fluctuating product availability, they have been seen to use lesser quality bolts. I've seen quite a few of them break.

Their bolt carriers are never in spec. I see poor finish quality, rough internal machining, insufficient torquing of the carrier key screws, poor staking, and they use poor quality fasteners. Generally they use unmarked no name fasteners, but I have seen ToolCraft carriers with inferior YFS screws. Their bolt carriers are almost always on the loosest possible end of tolerances, with poor internal machining and gas inefficient carriers.

All in all they're an ok, middle of the road bolt, but I don't like them on builds that will be used for accuracy, and I done like them on hard use duty guns that will be used in life or death situations.
 
Set up your phone to shoot slow motion video and see if you can capture what is happening. Sometimes over-gassed can have a way of looking like under-gassed. As in, it’s throwing the BCG back so hard it’s springing forward before the bolt catch can catch on the bolt so it’s catching on the carrier.

Not saying it’s not under-gassed, but if you keep having the problem it’s something to look at. One of my shooting partners had an issue like that with a new AR-10 and we did t know what it was until we took video. Turns out his set-screw in his gas block wasn’t as set as he thought. It was wide open. We thought under-gassed the whole time trying to diagnose.
 
"Did it lock back on the carrier and not the bolt?"

"yes"

There's your problem. The BCG should travel far enough to the rear for the bolt catch to catch the BOLT, not the carrier. Also, it SHOULD be impossible for the bolt to retract into the carrier unless the BCG is in the forward position, so there's nothing wrong with the BCG.

Your problem will be not enough gas for some reason, very likely the weak PMC ammo mentioned previously.
Also mentioned previously--you need to make sure the BCG is mechanically CAPABLE of retracting fully to the rear enough to lock on the BOLT, not the carrier. This is easy-insert an empty mag and pull the charging handle as far as you can until it stops. It should lock back on the bolt. If it will not do this, you have other mechanical problems like the wrong spring/buffer combination etc.

If it WILL lock back when operated manually, then the gas system may be at fault. But the first thing to do is try different ammo. Also, the BCG needs to be kept wet with oil during breakin, especially inside where the gas rings are. A couple drops in the exhaust holes on the carrier periodically will do.
This is the correct answer & explanation.

I've had it happen on a new gun with an AGB as I am tuning the gas & have not quite opened the AGB to the level needed to fully move the BCG enough to lock the bolt on the bolt stop.

With some mags it won't happen at all & the BCG won't hold open at all.

If the OP is not using an AGB, then the ammo is just to light or marginal for his BCG weight, & his buffer/spring combo to be reliable.

MM
 
Last edited:
This is the correct answer & explanation.

I've had it happen on a new gun with an AGB as I am tuning the gas & have not quite opened the AGB to the level needed to fully move the BCG enough to lock the bolt on the bolt stop.

With some mags it won't happen at all & the BCG with just hold open at all.

If the OP is not using an AGB, then the ammo is just to light or marginal for his BCG weight, & his buffer/spring combo to be reliable.

MM
it sounds like an under gassing issue. It could be a smaller gas port, an adjustable gas block, a leaking gas block or tube, a loose carrier key, worn gas rings, or too heavy of a buffer spring.
The ammo is underpowered, but if it worked before and the problem developed without changing any parts on the rifle it sounds like something has come loose and is reducing gas pressure. Most likely that would point to gas block, gas tube, carrier gas key, or gas rings.

Its also possible that your lube is reacting with another lube/cleaning product and congealing or gumming up and impeding cycling just ever so slightly
 
  • Like
Reactions: mtrmn and Milf Dots
At the indoor gun range this morning I fired 10rds from my Aero PRecision AR15 and after the last shot the BCG locked back but the bolt did not retract. This prevents me loading a full magazine. This is a new development on the new AR15 which has only been shot a total of 70rds. I used same ammo PMC 223A as before when there were no problems. I have been lubing both my AR15's with Mobil 1. The PSA AR15 has a PSA BCG and runs perfectly with this lube. The Aero Precision, with an expensive Tool Craft Nickle boron bolt and BCG, is the one giving me the problem. Perhaps I did not give the BCG enough lube. I need a little advise have from the cognoscente.

I don't think I've ever seen one get stuck on the bolt catch. It does lock back on a single round correct? And is this one you built?
 
What buffer weight? BCG could be out-running the mag spring pushing the bolt catch up, instead of true short stroking, missing the bolt and catching the carrier. Make sure that you can manually engage the catch on the bolt face and check the distance between the bolt face and the catch at full pull-back of the charging handle.
 
Its either out of time from too little gas or there's something up with either how you have the bolt together or your magazine.

Easiest thing to try is load 2 rounds in different mags. What happens?

Then try 5.56 ammo. If this works, try a few different mags with 5.56 too.

I'd also just take the bolt apart and put it back together again. In the process lube it (not crazy important) as well as check if you have any obvious wear marks already.
 
  • Like
Reactions: SilentStalkr
Before reloading pmc bronze was my go to plinking ammo.

We never had ftf or cycling problems, case after case for the family in various different ar's.

It was 33 cent ammo, better than most bulk cheap stuff we tried.
That used to be without agb, most cheap barrels are overgassed.
Mine were.

Your gun has a problem if it won't cycle it.

So you have a standard bcg, hopefully a conventional spring and buffer system that's also lubed, none of that fufu suff.

The easy swap of another bcg is the fastest way to vet that part of being the culprit, while your at it run it in the other gun as well.

While I had the bcg out I would check the gas rings alignment and do the opps check .

If it still fails go on to next part.

All the mentioned things to check are valid but I would isolate them one at a time unless you just feel like stripping everything for reassembling.

Then you would not know the culprit.

Merry Christmas deplorables.
 
  • Like
Reactions: BCP
@mtrmn care to elaborate on what part of what I said was funny?
The third paragraph. Maybe I'm a victim of propaganda, but you're the only person I've ever seen/heard say that Toolcraft BCGs are total crap. I own a few myself, even some so-called blems, and haven't been able to find a single flaw with any of them. They just work, and work well, without all the fluff and public relations garbage.
 
Same, your the first person I've heard with all of these Toolcraft bcg problems and broken bolts and out of spec parts. I've had zero issues with at least 40-50 I've built off of and I have a few here with 10's of thousands of rounds on them.. never seen or heard of a broken bolt on any of them or read any reports. I don't know anyone that even had to utilize their Lifetime Warranty

Toolcraft is well known and respected in the OEM market. You can talk about they don't make their bolts, but I can tell you that MOST big name BCG's you've come to love are outsourced and not made in house.. JP being one of them....
 
Last edited:
There are plenty out there with issues with Toolcraft BCGs and it will be common for a while but the caveat to this is damn near every single AR parts manufacturer has had at least some form of quality control issue since 2020. Also with the sheer amount of new people getting into the AR15 platform (and firearms in general), many of the so-called "complaints" will leave many of us face palming.

It's a numbers game though. When a million more people buy a certain product, even a 0.01% problem rate will start to seem astronomical with the amount of people posting online (especially on Reddit, like holy shit).

The most common issue I've seen in the past year with most BCGs is shallow staking and light torque (40 in/lbs instead of 50-60 in/lbs).
 
Last edited:
The third paragraph. Maybe I'm a victim of propaganda, but you're the only person I've ever seen/heard say that Toolcraft BCGs are total crap. I own a few myself, even some so-called blems, and haven't been able to find a single flaw with any of them. They just work, and work well, without all the fluff and public relations garbage.
they aren't total crap, but they're a good entry level BCG, but I don't consider them a high quality or long lasting part.
My question to anyone who think tool craft BCGs are great, have you ever gauged them? Have you looked at the internal finishing with a borescope, have you measured the gas runs, have you tested the torquing and staking on their BCGs? because quite a few of them fail those simple tests.

Their BCGs are made with loose tolerances and average QC. They're a good low cost option, but as far as OEM BCGs go they aren't the best, and fall well short of higher quality manufacturers like KAC, LMT, and my personal favorite Foreward Controls design.

Just an example of Toolcrafts 3rd party bolt breaking, here's a video of a guy who I personally know is good people, who broke 2 in a span of a few days
 
  • Like
Reactions: JS8588 and mtrmn
they aren't total crap, but they're a good entry level BCG, but I don't consider them a high quality or long lasting part.
My question to anyone who think tool craft BCGs are great, have you ever gauged them? Have you looked at the internal finishing with a borescope, have you measured the gas runs, have you tested the torquing and staking on their BCGs? because quite a few of them fail those simple tests.

Their BCGs are made with loose tolerances and average QC. They're a good low cost option, but as far as OEM BCGs go they aren't the best, and fall well short of higher quality manufacturers like KAC, LMT, and my personal favorite Foreward Controls design.

Just an example of Toolcrafts 3rd party bolt breaking, here's a video of a guy who I personally know is good people, who broke 2 in a span of a few days

Never had to inspect one that closely due to never had any problems. I haven't been able to watch the vid yet because of time constraints at the moment but I will soon.