"Best" BCG

**constructor** · 02-04-23, 08:53

Lysander, I understand you are saying why that specific set of pins. This isn't aimed at anyone in particular.

The title of the post is "best BCG". Since there are 2 main parts and either could be a contributing factor as to why they are or are not the best BCG you may want to check. All manufacturers do not hold the same tolerances and some allow parts that are "close" to tolerance to be sold, that is why BCM checks parts like they do.

Back when Obama was in office I had a very tough time finding enough carriers to meet the demand. I normally use Microbest but there was a 2 year period I could not get their carriers so I had to buy brands of lesser quality. I test fired every rifle and every upper we built, some did not lock back but would if the BCGs were swapped. Upon inspection I found the middle hole in the carriers to be larger than spec, that was letting gas escape around the tail of the bolt. The bore where the gas rings ride does not matter as much since the rings expand to make the seal. The fix is either use another carrier or enlarge the gas ports in the barrels, then what happens if the carriers are swapped again?

Most of the time the end consumer would not inspect 1 carrier, they would test and complain then test and complain some more then blame everyone involved while trying to figure out what the problem was. Over a 14 year period I have purchased enough parts to know which brands may have issues from time to time, some more often than others. Members here going back and forth with their opinions on which is good and which are questionable, I suggested checking the tolerances if they really want to KNOW which are better or worse as manufactured. Measuring the OD of parts is easy and most own a mic, measuring ID accurately is a little more costly.

As for sizes, use the drawings and buy the pins needed to check what you want to check, spec or wear.

Related, some companies manufacturing less expensive rifles use parts that are out of tolerance like I mentioned above. Rather than toss the questionable parts they enlarge the gas ports in the barrels to make sure they cycle and lock back to keep from getting returns. Not just carriers and bolts but, that is why many rifles come over-gassed.

**the AR-15 Junkie** · 02-04-23, 10:49

Originally Posted by lysander

Why do you think you will need those pin gauges?

Remember, he is measuring brand new components. If you feel the need to do the quality checks on all your components you buy, you might want to consider a better brand of parts...

He does all that measuring and gauging to show you which brands you don't need to worry about.

The gauges, you what are not the ones that check the parts against the drawings, you want the gauges to check for excess wear. The tail of the bolt show come from the factory with a diameter of 0.2501" to 0.2505", but how small can it get before you start having issues?

Why do you think you need to double post lol? Those are not even mine, I just posted the pic because someone asked for the specs SOTAR showed in their videos, these are the specs. If you dont agree with the #s, take it up with Chad.

**1168** · 02-04-23, 14:04

Originally Posted by the AR-15 Junkie

Why do you think you need to double post lol? Those are not even mine, I just posted the pic because someone asked for the specs SOTAR showed in their videos, these are the specs. If you dont agree with the #s, take it up with Chad.

I sometimes wonder if Lysander was involved in making the specs what they are.

**the AR-15 Junkie** · 02-04-23, 15:44

Originally Posted by 1168

I sometimes wonder if Lysander was involved in making the specs what they are.

I don't know, but I did read on another forum lysander is actually Reed Knights older son.

**pag23** · 02-04-23, 16:23

I like the Sionics NP3 that came with the upper I bought.....very slick

**bobcatdriver** · 02-04-23, 17:20

One thing I have learned after many years reading the forum, Toolcraft elicits the most negative and positive reviews. I used their BCG in my previous build for my son, and it runs just fine after I believe around 5000+ rds now. I had gotten it pretty cheap, around $50.00 on sale, and the only thing I really noticed on it was that the staking was a bit light. Not bad, but not real deep. That being said, I've seen much better staking on other Toolcraft examples. Just an observation.

**lysander** · 02-04-23, 19:46

Originally Posted by the AR-15 Junkie

Why do you think you need to double post lol? Those are not even mine, I just posted the pic because someone asked for the specs SOTAR showed in their videos, these are the specs. If you dont agree with the #s, take it up with Chad.

It's not you specifically, but the general notion that the end user needs to gauge and measure everything to feel they are getting good parts. As an end user, you should be able to trust your supplier that they are going to give you in-spec parts. And, people like SOTAR are a great resource to establish who to trust and who not to. You also have the experiences of others, and opinions of industry professionals to draw on. Save your money for ammunition, not gauges to see if the parts were made right, otherwise, you may as well buy one of these, because if the hardness is wrong, it's trash regardless if all of the dimensions are exactly nominal . . .

**BufordTJustice** · 02-04-23, 21:41

I was the one who originally asked about the pin gauges. I did not intend for this to devolve into compulsively checking all my carriers. This isn't needed as they are all BCM/Sionics/LMT/KAC. But I have many friends who bring their rigs to me for troubleshooting. The pin gauges are to help me save time as I assist others in diagnosing their (usually suppressed) AR's. Especially when occasional, mystery malfunctions are an issue and the gas key isn't in question.

I'm *very* thankful for all of the great info. Off to McMasterCarr I go (again).

I don't need all the gauges that SOTAR uses, not even close. I just want to put together a set of Go, Field, and No-Go gauges for the bolt tail and gas ring race.....maybe the gas key.

Telling people to "just buy an LMT" or other quality brand is vastly harder for a person to accept if they have.... say..... a Radian, DD, or other expensive gun/carrier, that it may STILL not be in spec. A few gauges allows me to remove any ambiguity and get them back in 100% operating condition much faster. And it removes some ego from the equation as well.

Sorry for the unintentional thread de-rail. The information and images are well received. Thank you to all who contributed.

Sent from my iPad using Tapatalk

**the AR-15 Junkie** · 02-04-23, 22:18

Originally Posted by BufordTJustice

I was the one who originally asked about the pin gauges. I did not intend for this to devolve into compulsively checking all my carriers. This isn't needed as they are all BCM/Sionics/LMT/KAC. But I have many friends who bring their rigs to me for troubleshooting. The pin gauges are to help me save time as I assist others in diagnosing their (usually suppressed) AR's. Especially when occasional, mystery malfunctions are an issue and the gas key isn't in question.

I'm *very* thankful for all of the great info. Off to McMasterCarr I go (again).

I don't need all the gauges that SOTAR uses, not even close. I just want to put together a set of Go, Field, and No-Go gauges for the bolt tail and gas ring race.....maybe the gas key.

Telling people to "just buy an LMT" or other quality brand is vastly harder for a person to accept if they have.... say..... a Radian, DD, or other expensive gun/carrier, that it may STILL not be in spec. A few gauges allows me to remove any ambiguity and get them back in 100% operating condition much faster. And it removes some ego from the equation as well.

Sorry for the unintentional thread de-rail. The information and images are well received. Thank you to all who contributed.

Sent from my iPad using Tapatalk

Check your PMs, sent you some more info.