The cam pin hole is technically a weak point in the regular design but I've never personally broken one either so it could be a solution to a problem that doesn't exist.
The cam pin hole is technically a weak point in the regular design but I've never personally broken one either so it could be a solution to a problem that doesn't exist.
Ive seen videos of them walking through their QC etc process for BCG’s but that could just be for the cameras. There’d be no way to tell for sure unless you work there. There point is they sell a BCG and most folks have good results with them. Whether they are an OEM or not is irrelevant unless you are trying to find the lowest possible cost by going directly to the source.
Here's the video. The continuity errors are interesting.
How many MicroBest failures have you seen (BCM's OEM)?
Personally Ive seen zero microbest failures. I think BCM bcg’s are overpriced and would rather buy a MicroBest and do my own upgrades to springs, etc but that doesn’t mean the BCM ones are junk.
Here is a great physical SOTAR did on 3 full chrome MB BCG’s and they all passed with flying colors (the only things he would change —> removing the donuts, swapping extractor springs out for sprinco 5 coil, and swapping the chrome extractor out for a phosphate one for more grip). For the $$$ MB is hard to beat:
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In general, I agree the bolt is more important than the carrier but having a good carrier regarding its dimensions and coating, etc. also is important. Look at all the different gauges He tests the carrier with in the below video. You could have the best most perfectly dimensioned bolt in the world, but if your carrier is sloppy in certain areas you would have a very inefficient and possibly unreliable gun. It takes two to tango.
These were purchased as "blems" and were basically still good to go...one slightly misaligned gas key.
These parts are manufactured on CNC machines, so they should be almost identical and in print every time.
Tool wear is monitored....we change tools before they are dull or worn and cause problems.
This is done automatically and monitored by the CNC machines computer today, the operator is notified of the tool change which can be automatically, or the machine stops and tells him to change a certain tool, and the part must pass inspection, again.
You are bar coded to the assigned CNC machine, with a bar coded job, the main personnel computer keeps track of every minute you are in the manufacturing facility and what you are doing.
Every competent manufacturer does that every day all day long throughout the year, if you are a world class manufacturer...scrap parts do not make it out of the facility.
I only saw one out of print part make it out of the faculty on 11 yrs. It was an airplane control panel with hundreds of features, but one hole was failed to be tapped.
The inspector who signed off on it as being completed and he inspected every feature was promptly fired for embarrassing the company, and sending out an incompleted part.
You are not allowed to possess a scrap part at your CNC station.
All scrap parts are labeled, tagged, and locked in quarantine, for the scrap metal recycling.
And no part can not leave your custody or unattended, unless surrendered to inspection with paperwork.
You set a part down outside the restroom, and go in to take a piss, that part is now out of your custody, no paperwork on it...you will lose your job instantly.
These gun tolerances are easy to hold in CNC manufacturing.
Modern manufacturers have real inspection departments, with modern electronic measuring machines.
This is rudimentary basic inspection with primitive tools.
They don't tell you how much out of round the hole is how much taper is present in each hole or the exact surface finish of that hole...but the go gauge goes and the no go does not...basic.
Does it taper out of print at the bottom or out of round out of print??
The guy from BCM mispronounced the name of the machine that measures surface finish RMS, that they spent a year making the video...so he probably just knows it has a smooth surface ...how smooth? He doesn't know.
We qualify our CNC machines to see if they are up to producing the parts accurately that they will be assigned to do...
It's much more involved that stated here but modern manufacturing is way ahead of what is going on here, ...at home inspection. Just the basics.
I didn’t post the video as an indictment against Microbest bcg’s, only as an example of the key dimensions in a carrier that get tested and need to be within a certain spec. All 3 of them did great but even though they came from the same manufacturer there was some slight variance on the internal dimensions (all still within spec though). A different manufacturer could have done a sloppier job on the internal carrier dimensions (not factoring in the thickness of the coating if applicable, etc.) and there’d be problems even with a perfect bolt….thats all Im saying
These were labeled as blems...so one might expect something to be almost out of print but operational.
So a little inspection would be prudent here.
We are in basic agreement, except the word "sloppy".
"If" ...you are paying attention in your manufacturing facility today, sloppy doesn't exist with CNC and electronic inspection.
Simple ...If you are a world class
manufacturer..."sloppy" does not exist today. Stringent manufacturing requirements have to be met and more are demanded of certain high tech companies to even bid on their jobs.
I've been in machining nuclear reactor refueling parts, DOD, robotics, computers, and aerospace.
We have engineers on the site to help with any ideas or manufacturing concerns, clean rooms for assembly, controlled environments in some CNC stations.
Temperature controlled machining, inspection, and assembly in some cases.
"Excellence in manufacturing", is on the front of the building and all the paperwork and letterheads.
All who work there adhere to that.
Any coatings and their thickness will be noted and tested...no significant deviations.
CNC manufacturering allows for perfection.
Bolt carrier dimensions are fairly loose, when compared to other precision parts. So there is no excuse for having one that's out of print in todays electronic manufacturing environment, to ever leave the facility.
But that doesn’t always happen especially in some lower end manufacturing companies or China made.
Or Boeing...the parts are falling off the plane in flight...talk about bad.
Would Elon Musk put sloppy manufacturing into SpaceX?
Absolutely not!
Engineering, science, machining, and inspection have to be at mankind's best.
So if Boing starts manufacturing bolt carriers, probably should do a little basic inspection, but alot of their parts will be good because they are machined outside Boeing's assembly plants.
Do you happen to know the acceptable tolerance variance with bolts and bcgs?
In other words, all these companies like BCM, SOLGW, Sionics, etc are just repacking BCG's they spec'd from MicroBest.
Of course they are even huge companies like Colt/FN/SIG farm it out to AO, Toolcraft, Microbest.
My 308 716i bolt carrier group is in the Microbest website pic lol. It's so fucking unique and goony looking that it can't be a coincidence.
I mean a huge company isn't making their own or doing the finishes in house but I'm supposed to believe a much smaller company is producing, finishing, QC'ing all theirs in a building 1/10th the size:
549$ lol, who the fuck you think you are KAC???
SIG 716i BOLT CARRIER ASSEMBLY
Factory replacement bolt carrier assembly for the SIG SAUER 716i TREAD.
www.sigsauer.com
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Of course they are even huge companies like Colt/FN/SIG farm it out to AO, Toolcraft, Microbest.
My 308 716i bolt carrier group is in the Microbest website pic lol. It's so fucking unique and goony looking that it can't be a coincidence.
I mean a huge company isn't making their own or doing the finishes in house but I'm supposed to believe a much smaller company is producing, finishing, QC'ing all theirs in a building 1/10th the size:
View attachment 8678137
549$ lol, who the fuck you think you are KAC???
SIG 716i BOLT CARRIER ASSEMBLY
Factory replacement bolt carrier assembly for the SIG SAUER 716i TREAD.
Of course. My point is the stories about coatings and QC are marketing to justify the 100% markup. The OEMs make a really good product, the extra $100 is for the logo.
I can remember when the BCM bolt carriers were like 139$ on sale, then they had price hikes to 169$ and now it's 199$, I like BCM but goddamn
Yep, most are contracted out, and may or may not have the same company machining their carriers from one year to the next.
Why one could notice a drop in quality from time to time...several different companies machining the AR bolt parts, carriers, bolts, springs, extractors, etc.
Just like Boeing, it has some fantastic parts contracted out, but when they assemble them the aircraft fuselage falls apart ...but the engines and landing gear are in great working order, as the structural integrity fails, and the top of the new fuselage comes apart in flight sucking out a passenger or two... a bad look for a major company, ... that will usually crash the business. It should have never happened, but it did, and continued.
Yeah,all ya gotta do is look it up. Most are pretty generous. There are specific requirements like ground or machined after heat treating. The cam pin as an example is one of those, the tolerance of plus nothing minus 1/2 thousandth on dia.
Similar holes in the carrier give ya .001" tolerance with a 32 RMS finish in several places, quite smooth, but nothing difficult...a CNC machine will make surface finishes 4 times smoother without polishing, with proper choice in tooling. Nothing here is difficult in modern machining.
One can make millions of parts holding a half thousandths of an inch, all year, and machining them very fast with 32 RMS finishes.
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AR-15 Bolt Carrier Groups, Components, & Parts - BCM®
bravocompanyusa.com
Edit: or are you saying they don’t actually manufacture their own bolts and carriers? Well yeah… almost none of them do.
What I like about BCM is that for the price they sell their branded stuff, they put a lot of effort into QC and material choice from their vendors. I’m not saying they’re the best, but you get a lot for your money with their bolts and BCGs.
Question from the OP was for the best bang for the buck … I think BCM’s up there.
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The bcm bcg’s are solid but @ $200 they are way overpriced IMO. The way I look at it is are they twice as good as a microbest with oks screws and sprinco springs that you can get for $92? Not even close.AR-15 Bolt Carrier Groups, Components, & Parts - BCM®
Edit: or are you saying they don’t actually manufacture their own bolts and carriers? Well yeah… almost none of them do.
What I like about BCM is that for the price they sell their branded stuff, they put a lot of effort into QC and material choice from their vendors. I’m not saying they’re the best, but you get a lot for your money with their bolts and BCGs.
Question from the OP was for the best bang for the buck … I think BCM’s up there.
Microbest BCG OCKS C158 HPT/MPI 5.56 BCG for Sale - Midwest Optics
Explore our selection of microbest 5.56 BCG for sale, including chrome and phosphate options. Upgrade your rifle with precision and reliability.
midwestoptics.net
Fair point…. Been awhile since I’ve purchased one and didn’t realize BCM had gotten so pricey.The bcm bcg’s are solid but @ $200 they are way overpriced IMO. The way I look at it is are they twice as good as a microbest with oks screws and sprinco springs that you can get for $92? Not even close.
Microbest BCG OCKS C158 HPT/MPI 5.56 BCG for Sale - Midwest Optics
Explore our selection of microbest 5.56 BCG for sale, including chrome and phosphate options. Upgrade your rifle with precision and reliability.
Will check out Microbest for my next one.
There are a lot of excellent options that are all superb choices. That said the most unique and truly functional one is the newest Griffin pocket one. I shoot full power 6 ARC with no ear protection because that thing makes it possible. That BCG is top notch quality but honestly so are many many others. What makes that one my current favorite is that it genuinely reduces sound at the shooter's ear. A lot of sound too. More than 10DB additional sound reduction when shooting suppressed--- there is literally no other product that even claims to try to do what that one actually does.
On the traditional metrics the difference between the top tier options are razor thin.
On the traditional metrics the difference between the top tier options are razor thin.
There was a time when all of that was true. Now you can buy BCM's supplier's unbranded and upgraded version for less than half of what BCM charges. Or for a few dollars more you can get any number better finishes than phosphate. These are high quality, no frills, commodity BCG's. The only real difference is the logo and the marketing.AR-15 Bolt Carrier Groups, Components, & Parts - BCM®
Edit: or are you saying they don’t actually manufacture their own bolts and carriers? Well yeah… almost none of them do.
What I like about BCM is that for the price they sell their branded stuff, they put a lot of effort into QC and material choice from their vendors. I’m not saying they’re the best, but you get a lot for your money with their bolts and BCGs.
Question from the OP was for the best bang for the buck … I think BCM’s up there.
Microbest BCG OCKS C158 HPT/MPI 5.56 BCG for Sale - Midwest Optics
Explore our selection of microbest 5.56 BCG for sale, including chrome and phosphate options. Upgrade your rifle with precision and reliability.
midwestoptics.net
Shop Microbest BCG+ Chrome w Phosphate Extractor OCKS C158 HPT/MPI 5.56 Bolt Carrier Group | Midwest Optics
The Microbest BCG has been designed from the ground up with the most avid shooters in mind, using only the best materials available on the market today. The
midwestoptics.net
I have had more issues with BCM BCGs than any other brand. A total of 3 carriers going down, 1 in a BCM gun, and 2 carriers in other guns. All were SBRs, and all were leaky keys. BCM did replace them all after a lot of coaxing (1 time had to get Pat Rogers involved), but I will never buy another.
Old Colt, Sionics and SOLGW make probably the best in spec carriers you can get.
Old Colt, Sionics and SOLGW make probably the best in spec carriers you can get.
Wow after hearing that and considering how grossly overpriced the BCM bcg’s are Im removing them from my OP list.
That’s very interesting for me. I have maybe a dozen rifles running BCM bolts, 4 of them SBRs, and have had zero bolt or bolt carrier related issues over 10+ years. Oldest one is more than 15 years old at this point, and has had the rings, etc. replaced at least 4 times…may have even swapped in a new BCM bolt at some point, but honestly don’t recall.
Those guns all get between 1-2K rounds run through them every year (each). Not a heavy firing schedule by any means, but enough to reveal any major issues for sure. We switched all the ranch guns to BCM bolts specifically because we saw some issues with other brands, and the BCM bolts just plain worked.
I wonder if BCM had a bad run of keys, or if the flat area where the key sits on the carrier wasn’t machined flat, or hell, maybe something as dumb as not being torqued to spec. Regardless, if you had that many issues, that points to a QC failure, not a one-off mechanical or material failure.
Were all yours made/purchased around the same time? Were they on different guns, or the same gun over a period of time? Wondering if something in the upper was stressing the gas key if it was on the same gun. Edit: re-read your post and see they were on different guns.
And again, I’m again amazed at the knowledge contained in this community…good to get new information and different perspectives!
And time for me to check all the guns! Microbest or maybe FCD just for the logo, LoL, may be getting a fair sized order soon!
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Radian and JP
Using my first Radian and am happy with it, Jp does some great work with the Bolts
Using my first Radian and am happy with it, Jp does some great work with the Bolts
I’ve never had any problems with BCM bolts. I have an 11.5" BCM upper that I ran hard, eventually shot out the barrel. When I swapped in a new Daniel Defense barrel, the original bolt still looked great, though I retired it at that point.
I bought that upper in 2014, and it started showing issues after about 1,000 rounds. The other two BCGs I purchased were from between 2015 and 2018. When I spoke with Chad at SOTAR about the issues, he mentioned there had been a couple of production runs where the gas key leaked and it was not something they were QC'ing at the time. Getting BCM to even acknowledge the issue was a hassle. When they finally replaced the BCGs, they didn’t provide any details about what was wrong, even after follow up.
That was also around the time Will Larson began working with Sionics to develop a perfectly in-spec AR and BCG. After the experience with BCM, it didn’t make sense to buy from them again, especially with companies like Sionics and now SOLGW committed to high standards.
ETA - they were all in different uppers.
