One of the great things about the AR-15 platform is its interchangeability of parts. This includes the ease of swapping a different bolt-carrier group into your rifle, which takes all of about 20 seconds. But some folks out on the Internet say, “Don’t mix and match AR-15 bolt-carrier groups!” Why not? Let’s ask Steve and Caleb…. who say AR-15s are all manufactured to the same specs, so a new bolt-carrier is almost certain to fit in your rifle. Just whip out the headspace gauges and check the headspace on the new BCG. You don’t even need a full set of headspace gauges. Just a NO-GO gauge is fine. (Don’t use a “field” gauge: that’s for military and law enforcement users who put a very large number of rounds through their rifles during training.)
Here’s another warning about mixing and matching bolt-carrier groups: Let’s say you have two BCGs that both headspace correctly in your rifle. You set one of them aside and shoot thousands of rounds with the other. Don’t just swap the “spare” BCG into the gun without checking the headspace again. The lug recesses in the barrel extension have worn while you were shooting with the other BCG, and the spare bolt-carrier group may no longer headspace correctly. How many rounds lead to significant wear? That varies by rifle, type of ammo, gas system pressure, and a lot of other factors. Suffice it to say, the average casual shooter is probably not going to significantly wear the headspace on their rifle any time soon.
So the myth is BUSTED, with a stipulation. You CAN change your AR-15’s bolt-carrier group IF you check the headspace when you do it.
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Just because you can say "I did it and nothing bad happened" doesn't mean you should keep doing it. We all know this guy right? Oh, and I said I would timestamp it! 4:27, Steve said check it!
Good topic, i was thinking of running the same bcg in two uppers
Algorithm.
Colt factory bcg worked perfectly with your SRN 180 300 Blackout upper. Built a lower for the 300 and bought a BRN bcg for it. Worked perfectly.
For some reason my 10/22 bolt won't fit in my AR platform rifle. Go figure.
I built a couple of AR308 DPMS builds. I have swopped bolts a few times to test a barrel issue. The barrel has a too tight chamber. I am working with the barrel manufacturer. I ordered another barrel from another builder.
Is it worth upgrading a ar10's bcg? And how would I know which one would work in my PSA PA10?
I have read that one barrel/bolt maker uses slightly different dimensions, at least on the 7.62×39 bolts. Special case? Don't know, but I do have the go/no go headspace guages on my wish list for the next order I make. You say I don't need the go guage, so I will keep that in mind.
I own my own gauges, because I like to be sure of safety gentlemen. Just makes sense to me.
Pick 1 to use forever a 12.5 BA or a 16" rosco bloodline?
How much does a Go/NO GO gauge fore headspace usually cost? If I buy a complete BCG because it was on sale what I usually do is drop the new BCG in each of my rifles and run 5 rounds through the gun to see if everything comes out ok and it always has turned out good but now this video has me thinking I may need a gauge to check and be sure
I use "go no go" gauges, that is about it.
Always good to check. It doesn't take a lot of time and it can save you a lot of headaches. Great video.
Can you show how to check the headspace next?
What percentage of guys in the USA that have built an AR-15 have checked their headspace? I bet less than 10%.
Thank you.
I sent out my bolt to a high level barrel maker so they could head space the barrel they were making for me. They told me it was completely unnecessary and asked me why i bothered.
Good Video/Info.
I have an old AR from the early 80's, that has easily over 10,000 rounds through it and, I have swapped the bolt carrier but, not the bolt. I've even had to change the lower parts because I was getting double fires. I also have another BCG that I swap between a 5.56 upper and a 300 BO upper without issue. Both have low round counts so, I don't worry too much about it.
Does the Army mix parts from different guns?
Dude, ditch the sideburns holy shit
One of the reasons I dumped the “Colt” product line is when they changed the internals (Green/Blue Labels) this was done to imply firearms owners were swapping parts to build “Machine Guns”.
M16 bolts or AR-15’s will interchange but that opens the door to “Intent” from Alphabet Agencies whose mission is to make innocents into criminals.
That said even “Mil-Spec” has tolerances and sone companies have proprietary parts Ex: Ruger.
I've been wondering about this topic. A friend asked me if he needed a spare BCG. I told him, if I had an AR, I would want a spare. I had heard that bolt lugs break off, or firing pins wear or break. I'll relay the message next time I see him.
I was under the impression that the A.R. platform was designed to be interchangeable, that you could take boxes of parts and slap together a rifle. So am I wrong? Or is that only with new parts? I don't know much about guns in general so don't hate on me for trying to learn.
Either pregnant or your not. Lol kinda…
Good advise.
I've had bolts that needed the gas rings replaced, after replacing them the rifle ran fine. Is this something that I need to be concerned about when it comes to head space?
I think it's a must but I tend to keep mine in the same upper so they wear together
I bought a go/no go gauge set and check headspace everytime i change a bcg…its just peace of mind.
How do you measure the headspace?
Video starts at 01:16
Here is a video worth watching after this myth buster – "Brownells Tech Tip: AR-15 Headspace". Thanks for the intel.
lol felt like this was a weird dad and son moment, yet I don't know if your related or who owns brownells. Like you were waiting for your dad to give the answer because your unsure. 0:45 1:40 5:50
How do you check the head space
I love you guys but the communication before shooting this video was not up to your usual standard lmao
Brand New i will use any , and an Ar i would have Blown one up 30 years back ? They match every one i have ever tried ?
So what you're saying is "If it fits it still may not ship" 😀
You guys do great work, thank you.
Holy cow, Caleb is hard to listen to. Like listening to Biden trying to avoid making a point or answering a question. ATFQ!
TL/DR Short answer seems is "yes". Thank you, Steve.
Then you get all the way to the end, after taking about exactly why the answer is yes and declare "busted". What is busted? Completely lost track of any logic in the word soup that this video turned into.
I was under the impression it's the bolt that matters, not so much the carrier. You swap carriers and use the same bolt with no issues.
Go/No Go gauges. Swap away
It would have been nice to see demonstrations.
Seeing as how I bought both my Stag arms upper and bcg from Brownells they should work together.
What do you gentlemen recomend for Elementary schools & Supermarkets /Cinemas??🥵😡😡
I'll give you one more – LWRCi and Sig 516 gas piston BCGs. Interestingly enough, they use the exact same measurements for piston rod extension and bolt strike face dimensions.
The ONLY difference is Sig uses an AR semi type bolt and LWRCi uses an M16 FA type. Both "separately" patented and ended up with the same bolt strike face locations. Conspiracy? Probably not. But fun fact for the day since piston systems are all almost completely unique.
So if you're in a pinch, you can get one of either.
Fort Jackson S.C. 1970, 1971 when we cleaned weapons many parts were mixed up. Nobody worried about that.
The only concern was the serial number of the M-16a1 matched your weapons card in the rifle rack.
Back at my Guard company in 1971 we were issued new Colt M-16a1. The geniuses at Camp Hartell engraved the bolt carrier with the lower receiver number. This was not any help.
After the first summer camp there was a group cleaning, all the bolts and upper receivers were mixed up. After yearly qualification firing, not one blew up.
30 years later talking to a machinest who had a contract with Colt, making tooling for gauging, I learned something the, tolerances were really tight.
Normally I would not mix bolts and upper receivers, but would check the head space if I had any doubts.