"Sitting back watching action movies..." STOP SPYING ON ME WHEN I CLEAN MY RIFLE!

So it's probably a good idea to keep at least one spare bolt in the tool kit.

I've been around AR's, M-16's and M4's for years in the military and civilian side, and I've never seen a bolt failure. It was only a myth all these years, thanks for showing the results of bolt failure. Also, though we feel attacked on watching movies while cleaning guns, that's a great point to consider as we could miss a small detail that could lead to a catastrophic failure at the most inopportune time. Thanks for a great video

"cleaning your gun, watching action movies" I feel personally attacked! Only the finest 80s b movies in this house.

Thanks for another great upload. School of the American Rifle should be required viewing for anyone utilizing the AR platform. Information on this channel is priceless.

Understanding common failure modes is very helpful, so we can know what to look for. Thanks for the videos you make!

One thing when they apply the NiB coating is that they need to activate the hardened surface of the steel with hydrochloric acid, causing a high probability of hydrogen embrittlement. If they’re not baking for the hydrogen embrittlement relief after the plating process, you will get fractures in the high strain areas prematurely. JP bolts have larger radii on there bolt logs to reduce the stress risers.

Thank you so much always heard of these failures but never saw them

It's always a good idea to keep a spare AK close by just in case your AR15 breaks again.

As a Metallurgist with some knowledge of Failure Analysis and Fracture Mechanics this was Fascinating. At the risk of being a know it all the failures all appear to be Brittle failure and at obvious stress concentrations. There appears to have been little to no attempt made to reduce the stress concentrations. In addition case hardening exacerbates this problem

I had a bolt out of an older Bushmaster crack, but not break. Rifle started to jam, a lot. I still have it in my parts drawer. How is it that this page only has 32.9k subs? This is one of the most informative pages on YT. Until I found this page, I had no idea most of these gauges and tools existed.

I feel like having an AR is the same as having a bucket of survival food. It makes you feel better for having one, but deep down you know it won't last, and you hate to think that one day it may be all you got.

Nice collection of bolt failures. Definitely great advice on taking time to inspect your bolt for possible issues before a catastrophic failure.

Thank you for the educational examples. I don't shoot a lot but thought I had been around the block at least a little bit and never even knew that could happen let alone multiple examples

I have never watched a video of yours and not learned something. Thank you!

When I'm cleaning I am inspecting as well. I was waiting for you to say why these bolts are failing.

Thanks for the vital information regarding bolts that have failed.

Thank you for your channel sir. Your wealth of knowledge and generosity to share is very much appreciated.

No clue why but I find these really interesting hahaha. Your ocd and organization skills are fun to watch

I wish you had some round count info for these bolts. Also how much full-auto they saw.

Man, making have to breakdown my gear and actually inspect it! _This is my rifle, this is my gun..._ Do so love learning about the nuance and intricacies of the AR-platform. Left more and more in awe of designers and engineers who once upon a time did things with just pen and paper.

This is tremendous content - a real public education service. Keep it coming.

I am a former Army Sergeant and company armorer. We never replaced parts unless they broke, or if an issue was reported to us by the issued operator. The problem is the FNGs (

Sheared locking lugs are endemic in GI rifles after the introduction of the +P M855A2 ammo.

Excellent tutorial! Cleaning is the first step in inspecting.

My two sons and I shoot NRA matches, FTR and Service Rifle. One thing I've learned over the years from having to stop and repair rifles during the middle of a match, I keep a spare of almost everything in the tool box.

Wow that is really great and nformative. Seeing examples of the failures gives you an idea where to take extra time to look at.

Finally, someone who gets to the point & shows real, quality firearm information. SUBSCRIBED

Great video! Nice to actually see what can happen. Definitely always good to have spare parts on hand, including populated bolt heads and even entire bolt carrier assemblies and more.

Bro, i just want to thank you.. im an avid firearms enthusiast.. mostly pistols... Ive been a pistol guy my whole life.. i keep all my buddies 1911s up and running, all their and my glocks , czs and clones ect.... Im a pretty good pistolsmith too.. so i know the lingo, the concepts, and all that comes with it... I finnaly made the jump into the ar platform last with with a bonus check from work.. purchased a used m&p15 lower, ( got it for 20 bucks because the trigger guard ear was broken.) Bought. Daniel defense intrgrated triggerguard and grip to hide that, and a parts kit.. the lower was pretty straight forward... I had all that assembled in 20 minutes . My problems came with the upper, and lining up the gas holes, and the gas key with the tube itself. Had a little overhang on my feed ramps too.. not enough to fool with considering i learned in your video that its not neccisarry unless my rounds contact the lower reciever ramps first.. in which case theres a problem... You videos helped me go from nothing but parts, to a functioning , accurate, beautiful rifle i have the pride of saying i built with my own hands .. thanks for you passion man..

I literally learn from every video you do. Thank you for your work!

Wow. Lots of comments asking for specific user history of each bolt. It doesn’t seem like that was the purpose of this video. This video does an excellent job showing how a bolt fails (weakest points) and where to inspect for damage leading to failure. That’s all. Everything mechanical can fail, and can fail early in some conditions, all you can do is buy quality components (primary and spares) and do your inspections.

Good reason to own a good magnifier headset. Thanks for another great video! I learn something new every time.

Very good info and tips on what to look for while cleaning.

I had a lug break off a bolt out of my basic training issued m-16. I was in the middle of a practice qual when it happened. Lol

This is a very good video, I have shared to my own group. Inspection for cracks like we see here should be part of any cleaning or maintenance procedure

you are a great You Tuber, straight to the point and educational. Thank you sir for your education.

I seem to learn something every time I watch,,,, keep up the good work !

I was issued an M-4 while in gov’t service. The bolt broke while shooting frangible ammunition in a shooting house. Frangible ammo pressures have a reputation for breaking bolts. It was common to carry a spare bolt inside the pistol grip of the M-4. Never did that for any other rifle.

This is extremely educational. Thank you for sharing this.

Very interesting video. Now I know what to look for when inspecting.

I think I'll inspect my bolts a lot closer from now on. They take a hell of a beating, I'm actually amazed they last as long as they do.

i feel like a solid way to prevent or prolong the issue from happening would be to radius all hard edges like around the extractor and cam pin hole and firing pin pass through on the cam pin radiused/chamfer greatly strengthens the edge. hard edges inside high stress parts are know failure points. can be found in high torque/pressure situation like in prop shafts in both aviation and nautical vessels. Kieth over at turn right machine works dropped that info on the world during one of his vids. really helped me understand the importance of breaking the edges and avoiding cutting hard edges in the depths of something like a keyway. or in this case an extractor cutout. if u want to do some redesign i would recommend doing an extractor cutout in the radiused bottom with round tip ball mill and making an extractor with a matching surface and redoing the locking lugs with a radiused edge it will reduce lockup surface but fairly certain it would still have a % over safe operating peramiters.

Could it be stress risers at the extractor slot? And would deburring/polishing/smoothing do any good or is it moot?

So the moral of the story is no matter who makes it, if you run it hard enough for long enough you can tear just about anything up.

Thank you for sharing your knowledge!

Having spent some time in the Army when I hear infomercials saying " built to military specs!" I know most of the time it's junk. Bolt failures with even a brand new kit is very common in the service. It's funny I've never had one on my custom built rifles with non- mil spec bolts, but a great reputation have not failed with a ton of rounds.

Thanks for all you do

Thanx for the heads up on where to look specifically

I had a bolt lose a lug and break at the cam pin hole in my issued M4 while i was in the Marine Corps. The most common failure I experienced however was with the burst trigger assembly, I had 3 disconnectors break on me. it was so bad it was funny until i was finally graced with a new M4 from the Army.

Excellent info on this!!

And this is why you buy S7 bolts which are between 30 and 100% stronger than C158. Steel has come a long way in 60 years.

I'm new to your channel, videos are very well done, informative, and thorough. Would like your opinion on one thing though, lubrication of an AR especially the bolt carrier group. There's a lot of videos on lubricating the AR (wet minimal and everything in between). My question is your thoughts on lubricating the AR, especially the bolt and where? I'm pretty sure you've seen most everything and the effects. Thanks

There must be something to it that the lugs that failed are all unsupported metal on one side. So inspect all lugs for damage but the lugs next to the extractor are the most likely to fail

always been an AK guy just got into ARs been watching all of your videos it amazes me at how many failure points the AR has never seen anything like this with com block AKs

Very informative short and sweet too the point. Great video. Ypu just got a new subscriber

Mine snapped today so I'm doing a little research. Thanks for the info

I just learned a bunch of stuff. Thanks!

Oh great, I've got a Raineer Arms bolt carrier group... I'm glad they have a lifetime warranty... but also, I'm using it in a 20 inch standard DI gun... which hopefully isn't as stressful for it as say a shorter gas system... Yeah, what would be the best bolt to keep in my spare parts kit in the back of the rifle.. possibly... the JPE Enhanced bolt made from SAE 9310 is a good choice??

ALWAYS great information... Great channel.

I've heard of this happening but never actually seen it. I have a BCM upper with about 9000 rounds through it and that bolt is still fine (so far).

Wow! Great video. I have several questions if I may. > Why are the lugs adjacent to the ejector the ones directly affected? You mentioned government contracts M4/M16. > You happened to have the makes? > Is overgassing possibly the culprit? Thanks in advance.

Very interesting. Thanks for posting.

Careful inspection while cleaning made me see a safety flaw in an after-market Glock slide. The firing pin safety worked the first time each time the slide was assembled but it would not reset consistently. Extremely good advice!

Learning as I go. Great info

Ima be sure to pick up spare parts now. You got me paranoid 😭

Wow! Altho I have an AR and was previously very familiar with them from time in Service, I never saw a bolt failure. Do you think it was because of extensive full-auto use, being slightly out of battery, or possibly a too-high pressure load? I reload for my rifles (& pistols) and am very careful to stay below max loads plus, I don’t yet have any class 3 weapons, so no auto fun switch. Thanks for the video. I know what to look for now. Also, I noticed these were all 556/223 bolts, do 7.62 bolts also fail? At same rate and for same reasons?

Thank you from Barcelona (Spain)

Those Rainier bolts looks like my Barnes Precision bolts that broke the same way. Stamping 100% identical. I wonder if they produced for Rainier.

Never a bad idea to have a few spare BCG around.

Have a Aim Surplus nib bolt that sheared a lug off next to the extractor last night after I cleaned my rifle and sent the bolt home.I pulled back on the charging handle and it wouldn't budge so by having to motor the gun to get the bolt to unlock off came the lug. Working with them now for a replacement but this bolt had less than 600 rounds fired. Passed head space clearance when I put the rifle together and it cycled well with no failures till this happened. So you never know, heat treat, etc etc...

Cam pin hole or lug(s) cracking-failures are both examples of reduction in cross sectional area.

Great info! 👍🏻👊🏻💥

Very educational as I’ve never seen bolt failure in the Army or civilian shooting

Back in the mid to late 1980’s, the AR-15 was MY DREAM GUN! An older military guy with an FFL who hunted with us was always breaking out his M-16 and doing a couple of mag dumps. I wanted an AR-15 so bad, I just couldn’t imagine they would be so affordable or obtainable as they are these days.

Great help on one of my builds had a feeding issue good ol dremel bullet sharpening stone took off about 3thou and polished the ramps all good i would love to buy one of your patches or stickers?

I broke a bolt where the cam pin enters. It broke in two. It was off a American tactical 7.5 pistol. It was the first ar I bought and had the polymer upper and lower. The upper broke at the take down pins 300 rounds in. The bolt broke at 900 rounds. I then sold it and bought a bcm and haven’t looked back.

That's really interesting and disturbing at the same time. Most people think of bolt failures as things that happen to others, but seeing a table full of them screams "check your bolt and lugs thoroughly when cleaning your rifle " That brings up an interesting thought- regular cleaning isn't a "thing" like it was when I was in the service. Modern AR rifles function very well, even when filthy, but if you don't clean it, are you checking and inspecting it? I'll be far more attentive going forward

Would slightly rounding off the 2 lugs next to the extractor IE like a KAC bolt be a possible solution or lower the risk? Seems like it could work out good, just not sure about pressure and bolt lock up though

Another Excellent Simple Video Brother

Thanks for the good lesson.

my bolt broke in half on the bolt face in bootcamp. It was an M16A2 back in June 2010.

Very good information. Thanks.

Thank you for the information.

Damn… Love my milled receiver AKM-47… Never seen this type of failure on mine.

Did you clean the grease and/or oil off of these bolts, or were they just ran dry ?? They look dry to me.

Great video!

Good to know. Thanks for the info 👍

This is why you should keep a spare bolt with your rifle, along with enough spare parts to make a spare rifle. "Two is one and one is none".

Great video! Thanks.

Ive got over 50,000rds suppresed 5.56 through my mk18. Im on my 2nd barrel, about to be on my 3rd and the same bcm bolt for all the ammo Ive put through it. If headspace was within limits for those bolts, what caused them to fail? Deep micro imperfections in the steel? Overcharged loads?

Thanks for the heads up, ill consider it some other time, on my 3rd action movie at the moment waiting for pizza delivery.

Good info, never seen a bolt failure like that but have seen mushrooming of the lugs, cracked and missing lugs and cracked extractors. I curious on how the bolt cracked like that near the cam bolt if carbon build up was the cause those bolts didn’t look that dirty but if you threw them in a cleaner that would explain it.

Great reminder about proper inspection. I have certainly been guilty of hustling thru a cleaning occasionally,,. Just wanna "get it done", gotta dedicate more time, be more thorough. Great heads up 👍🇺🇸👍

Very educational as always. Do we have a round count on the cam pin hole failures?

Valuable info!! Thank you!!!

Hey Chad, love all the info you provide. What are your thoughts/opinions on the Midwest Industries bcg’s? I picked up their nitride version for a build bc it’s what I could get at the time & only bc the extractor has a phosphate & not a nitride finish. The build is not complete yet so I have no rounds through it but I was jw if I made a good choice? Thank you sir & to any other input from the community.

Great video. is there a life expectancy for the average bolt? Appreciate your input and recommendation.

I'm so happy you're back to regular uploads

Thank you so much for this content!