It always surprises me when Ian explains the topic in the first 30 seconds, but then continues to give us a stream of useful info for the next 10 minutes plus

The thickness of a sheet of paper is the difference between too short and too long. Well said sir.

If Firearms 101 was a college class, Ian would be the professor that everybody on campus wants to get.

Overlaying a physical bullet onto a diagram ,while explaining different processes & issues, really helps to understand them better. Please do some more like this in the future.

I'm a technical illustrator, have been for twenty years. Your illustration of headspace is top notch. In my defense, I often have to illustrate something explained to me by someone who is not good at explaining. You obviously know what you're talking about, and you're good at explaining. Those two don't always go hand in hand.

Videos with Ian explaining these kinds of topics are great

Ian hit it on the "head" with this answer! I work at FN America in Columbia SC as a barrel QA technician in the barrel shop. This is exactly what headspace is and the importance of it being correct. If you have the experience and means to get the gages to check it , do it. If not please don't try. Excellent video on this topic Ian!

Ah, headspace and timing! Essential Marine Corps training for the Ma Duece 50 cal. Brings back fond memories .

Should have answered this the way my drill sergeant did for a private in my basic training: "headspace is the thing that stops your face from getting blown off, private".

I’ve known and been checking headspace on various rifle platforms for years now, that being said this was extremely informative and easy to understand for those who didn’t know or understand it.

I had an SMLE with blown out headspace, so, of course, it was non-firing and used as a wall hanger. A certain thief stole it, along with other items, and the police were unable to find said thief. I often wondered if they ever tried to fire it.

It’s easy to forget until you see a video like this just how ingenious a design a modern firearm is. Probably why the design hasn’t really changed much in the last 100 plus years - it’s hard to improve on such a fundamentally sound design.

Headspacing is one of those firearms concepts that can be tricky to understand, thanks for a thorough and concise explanation . I never tire of content like this.

I'd just like to point out that there are situations where a headspace issue is less obvious, meaning that the weapon can appear to be cycling fine for several hundred or thousands of rounds, and then suddenly detonate. Typically what happens is a minor case of the situation you were describing @4:50 but instead of the spent case producing an evident indication, what happens is the locking lugs become fatigued from repeated impact of slamming that short distance, until either the bolt lugs shear or the trunnion lugs shear.

Class is in session. Professor Gun Jesus teaches more about head space in 10 minutes using hand drawn diagrams with an actual cartridge overlay than probably 90+% of us knew from years of being pew-thusiasts. Yet another reason to live this channel. Thanks Ian. Merry Christmas! May all of your head spaces be just right, your Scotch be a fine single malt and your shots be inside the 10 ring.

I used to run the calibration lab on the USS Carl Vinson. We calibrated everything. From headspace gauges to rubidium oscillators. Oscilloscopes, spectrum analyzers. It was good.

It's really important if you want to have a properly functioning, safe and accurate firearm. If you have too loose a tolerance you will find that the brass backs out of the chamber under pressure and ruptures at the case head (bottom of the brass) which vents hot gas at the shooter, or has too large a gap to jump the projectile to the rifling which causes accuracy issues, among others. I've experienced both but never severely. I've also seen a few Lee Enfield conversions which had such severe headspace issues they ruptured every case they fired just above the case head. I immediately told that shooter the short explanation and that he really should take it to a gunsmith to fix. I never saw him again but I hope he listened. Awesome work on the video, Ian, and a really good illustration on what the problem is and how to identify it! As always, keep up the good stuff.

These videos are arguably my favourite. Helps you to understand a lot more of what the weapon rundown videos are actually talking about.

I bought Go/No-Go gauges for checking headspace on some surplus stuff. Check them every time. I've found a few that weren't cleanly passing at a major retail chain. I did notify the staff.

I was waiting for you to mention the Turkish SMLE conversion. Thanks for making it so simple for us not very technical firearm lovers out there.

Ian, i know you've made lots of these q&a videos, but I just have to say I love the format

Excellent explanation of headspace and why it matters. I really enjoy building as much as I do collecting, and I frequently get asked for tips on building (especially AKs), and I'm always having to give a lecture on how important headspacing is. Now I can just link this video!

I thought about a set of go/no-go guages when building my first AR. Fortunately on that platform, upper receivers aren't really critical to achieving proper headspace. I just bought a bolt carrier group and a barrel from the same manufacturer, and said YOLO. Brass looks great and it's the most accurate gun I own.

Very very good video! When I bought my (brand new) AK here in Austria a few months ago - having no previous practical experience with guns - the guys in the gun shop DID NOT KNOW THE TERM HEADSPACE ! When I told them that I heard a lot about headspacing on videos of Brandon Herrera and other people, they said something like Headspacing would surely only be some problem of the americans and that they don't have that kind of issues with their guns in the shop... Later I found out that they primarily sell AR-style Rifles and only the expensive kind, they don't really build guns themselves (only minor repairs and stuff like that). So they might never have had issues with improper headspacing (of course they only use best-of-the-best ammo, too). But still, this should have been a major NO-GO for me. Now I know better and with Ians excellent explanation, I know why it is really important.

Excellent video!, and I'm glad that another engineer, 10,000 km from my house has the same hand-CAD skills as me. Greetings from Argentine Patagonia.

Just in the first thirty seconds you explained this so much clearer than any other I have seen! So many seem to make this so difficult to understand…especially to new firearms owners and new reloaders!

This explains the "why" of belted magnum cartridges: that massive back end is not to prevent blowouts, but to ensure the headspacing is perfect for those high pressure rounds.

Super explanation, Ian! And one can clearly see how Hybrid (Stainless Steel) base on the cartridge case allows higher pressures and no blowout until the pressure is dropping as the bullet travels down the barrel, and then unlocks the bolt, still at higher pressure, and the case base is strong enough during extraction with higher camber pressure! Good place to show this on your super diagram!! ❤

Excellent video, and definitely one of your most informative "intro to firearms terminology" sorts of videos. I hope novices 20 years from now will still be learning from this. Keep it up Ian!

Another Rifle that is notorious for headspace, is the No.5 Rolling Blocks in 7mm Mauser. Due to the change in the case dimensions in 1910s, modern 7mm mauser usually doesn't headspace correctly in the old Rolling blocks

I like how this video bleeds into how to look at older guns that were re-chambered, etc.

Excellent explanation and advice. I had a.222 that I handloaded for about 35 years ago. Inherited from my Dad, who bought it from a neighbor. All went well, until I had a case separation due to excessice headspace. Luckily, I was wearing shooting glasses and escaped injury when the case ruptured...

As someone interested in the engineering on firearms I always wondered what headspacing was. Thank you Ian!

This was a very good basic explanation of headspace and its role in safely firing the firearm. I would like to see follow-up videos on ways of achieving headspace. Rimmed cartridges versus belted cartridges versus semi-rimmed versus shouldered versus head spacing on the case mouth. All but semi-rimmed have their advantages. Secondly I would like to see the effect of headspace on accuracy particularly in the case of 38 Super where it is a semi-rimmed cartridge but gets increased accuracy when the firearm is set up for to headspace on the case mouth. And finally it would be nice to see a comparison of say a military chamber versus a match or even bench rest chamber. There used to be guys that would shoot an entire benchrest match with one casing! Punching out the primer between shots priming it with a hand primer measuring the powder charge and seating the Bullet by hand. And yes when it comes to stating something in the first 30 seconds and then rambling on for a stream of Consciousness for 10 minutes I'll try and give Ian a run for his money!

Would love to see more videos like this. I like the old obscure gun videos you primarily put out but this is some useful information that can save someone from injury or worse. Great content as always.

Great explanation. A really crucial piece of information for weapons which get frequent barrel changes - M2, Mg-42, etc.

This is one of the best explanations of headspace I have ever seen.

I actually remember this. In training, with good ole Ma-Deuce, we had a go-no-go gauge to check the head space and timing. Of course when some "other" soldier was missing the target (not me, I always hit what I aimed at) the soldier would say that the head space was off. The drill sergeant replied, "Yeah, I think you're right, the Operator head space and timing is off !"

My roommate had a sporterized 1917 Enfield. We took it out back to try out a couple of old guns. I loaded it up with Ferderal .30-06 and fired it. It felt like I had been hit in the cheek with a hammer. The case had burst from the head to about an inch up the case wall. Gas shot down the bolt track, blew out the bolt release, singeing the skin on my thumb and blasting gas and unburnt powder into my face. I touched my face to find blood. The powder had been lodged in my skin leaving a perfect outline of my safety glasses. I spent the next week picking grains of powder out of my face.

Great explanation and illustrations Ian! Thank you! I have always purchased headspace gauges for military surplus rifles…

While in the Army I went to an armorers course to learn how to operate, maintain and repair many various weapon systems including the M2 .50 cal and M240 machine guns. The M2 needed to have the headspace checked whenever the barrel was installed which was a simple process and took less than a minute. The barrels of M2s were not assigned to a single weapon and were interchangeable between different machine guns, and because of that, the headspace had to be checked and adjusted. The M240 did not have to have the headspace checked since the barrels were assigned to that weapon by serial number. They were not interchangeable across different weapons. In our classroom there were some examples of machine guns mounted on the wall that did not proper headspace set. It showed weapons that had catastrophic explosions that completely destroyed receivers and barrels, and of course the instructors had stories of what happened to the operators of those weapons. The stories were probably made up but point taken - someone got messed up when those things exploded.

I may not be an expert on firearms, but videos by Ian like this one sure have increased my firearms knowledge by a lot.

I wanted to buy the CZ-457 rifle with the three barrel set (17HMR, 22LR, and 22WMR) but it was unavailable so I bought the rifle in 22LR and barrels for the other two calibers separately. Being new to shooting I had no idea about head space until I read the warning about checking it from CZ. So I did my homework and educated myself on what it was, how to check it, and then do the fix if needed. I went local at first and every gunsmith I asked told me to "Just shoot it and see." So that didn't sound right and I bought the 'go', 'no-go' gauges which in itself turned out to be a wild goose chase as they weren't immediately available. I eventually waited for a run to be made on the 22 rimfire gages and got the job done. In the end it just made me a better shooter. Also, I wouldn't let a gunsmith in my city change the batteries in my flashlight let alone do anything to my guns. "Just shoot it...." lol.

An example of a headspace problem happened to me. I bought one of the surplus Italian Army Carcano 6.5 mm rifles about the same time Lee Harvey Oswald bought his. The things were dirt cheap. I think mine was $16 or $17. I also got some surplus ammo. I noticed that the bolt rattled a bit. It tightened up a little with a round in the chamber, but was still sort of loose. The first time I shot it a spray of debris hit me in the forehead, above my right eye. I put on a pair of sunglasses (as an ad-hoc substitute for shooters safety glasses) and fired again (I know, a stupid thing to do, but I was 15). Same thing happened, a spray of dirt and unburned Italian smokeless powder hit me in the forehead. The next thing I did was a little smarter; I never shot the rifle again.

Ian has come a long way since he started. Good presentation. 😊

There are a number of western weapons that utilize what is known as "crush-up" - that is, the minimum length chamber is a little shorter than the maximum length cartridge, in order to mitigate the effects of a compliant breach, or thermal expansion from extended firing. The 1918 BAR, M1 Garand, M60, M249 and M240 all utilize "crush-up." The minimum M240 chamber is .010" shorter than the maximum cartridge. An explanation of this concept can be found in Technical Notes Small Arms Design by John Rocha, which has been featured on this channel before.

Ian, thank you for your wonderful illustrations!

Old Lee Enfield rifles are notorious for headspace issues. At my range we have 303 gauges to check them. Old beat up 303 show up all the time and we have had some accidents. It’s now part of the service to offer a free quick check to shooters.

Thanks! Always enjoy your videos. I particularly appreciated this one.

Really well detailed and interesting this style of QA is definitely a success, that isn't to say that I don't miss the hour long ones as well.

In the 80's setting up a M-1919 Browning was easy if you didn't have the gauges handy-in Canada we used a nickle and dime. Convenient for all of us in a hurry. Go and no-go so you knew for sure. Resetting the headspace was a bother but considering what could happen made it worthwhile.

Also advisable to have headspace checked if your AR barrel and AR bolt were purchased separately. My local gunsmith charged me $2 and it took 60 seconds. AND if you use the thing defensively, a receipt for a headspace check can demonstrate that you are safe & responsible.

The best explanation I have seen yet. ESPECIALLY with your diagrams, great job...

Great video; nice tip on head-spacing when building a firearm from parts; I built semi, closed bolt Mk-2 and Mk-3 Stens and they work great. However, I want to mention that while building & testing: I had one 'blowback' experience when I put in too light of a recoil spring in accidently; Very glad I was wearing eye protection as the blast pressure found every place where my shooting glasses leaked, woke me up. The semi-Sten has 2-springs instead of one and the spring travel-length sort of leaves it almost loose when closed & loaded, then has an over-tight 'accelerated spring compression when cocked back past the sear locking point to the bolt-stop. I might try an Uzi recoil spring. The surplus WW-2 mags worked great, most were stored well and 70% weren't worn out. The closed-bolt semi-Sten doesn't jam and feeds hollow points and flat-noses easily when Uzi only takes FMJ ammo.

*"head space and timing"* to be precise but absolutely spot on here.

Not a headspace issue, but similar: One time when I was at the range, one of the range officers came over to me and asked if another guy could use one of my cleaning products. He'd seen I had a kind of "blast-free" cleaner and another guy at the range had managed to get loose powder inside his gun. I went over to see and found that the guy was using reloads in his .223 bolt-action and was using 60+ grain bullets in what was designed to be a varmint rifle. He'd set the bullets too far forward in the brass or the rifle wasn't built for that heavy/long a bullet (varmint loads are usually under 45 grains), so when he chambered a round, the bullet was rammed into the rifling. If he fired the round, it was no big deal, but when he tried to clear the chamber at the end of a relay, the bullet had remained stuck in the rifling as the brass was extracted, letting the powder pour out of the case. More importantly, the bullet was still in the barrel, something neither the shooter nor the range officer had realized. If he'd chambered another round and forced the action closed hard enough, it would have shoved the bullet of the new round back into the case, pushed the old bullet deeper, or both. This can also happen with too little headspace.

Thought I knew what headspace was but more to it than realized. Ian is an outstanding teacher!

As I recall from reading, setting the headspace on Maxim-action machine guns (including Vickers) is both important and a bit complicated.

As someone getting into just getting into gunsmithing for 3 gun competitions, this was timely and highly informative, thank you.

I can 100% confirm excess headspace creates fun. Had this with a 22lr upper I had where the barrel liner was not properly secured. What happened was I was shooting suppressed and did not realize that my barrel liner was ever so slowly moving forward. I eventually learned this when one cartridge blew out toward the back and made a boom that left my right ear ringing for hours, might pay for that in the future. Can't image what that would be like with say .223 or 9mm. Had to take it to a gun smith that epoxyed the liner in place. My guess is it was just pressed into place by the maker.

Regarding the ability of brass to expand, I found that out *almost the hard way last week. Somehow, a 5.56x45 cartridge wound up as the first round in my 7.62x39 AK magazine. I loaded it into my AK, pulled the charging handle back, released it, and noticed the bolt did not go all the way into batter. I pulled it back again to visually confirm nothing was in the way, and tapped it forward to manually close it. I pulled the trigger and there was a small puff out the muzzle and the bolt didnt cycle. I removed the magazine, locked the bolt back (thank you Zastava for a safety lever that do that), and the case didnt come out. It took very little effort to pry it out with a pocket knife and the front 1/3 of the 5.56 shell from the shoulder back had swollen to fill the 7.62mm chamber. If it had been poorly made ammo or steel cased, I likely would have had a catastrophic failue

It's always a pleasure when somebody asks the right question and give Ian the opportunity to create such an informative video answer. Thank you for asking !!!

Great video , as always. Am a bit surprised that headspace tolerance between rimmed, semi-rimmed and rimless cartridges was not really explained. Rimmed cartridges are MUCH more forgiving of headspace tolerances, as the rim is actually part of the headspace. I own an SMLE in .303 British rimmed and discovered while rebuilding it that the gun safely fires with the original, very worn bolt head and the replacement ,newer bolt head. The replacement bolt head locks up much tighter than the original, but there is no case deformation nor gas leakage using either bolt head. As an aside, I rebuilt a CETME clone by replacing the worn bolt head and rollers with a new bolt head and +.04mm rollers. Although it uses a rimless NATO round (and was borderline out of headspace tolerances), the CETME clone safely fired with no case deformation using both the original , out of spec bolt head/rollers and the replacement bolt head and rollers. My dollars worth-John in Texas

Ian, this is exactly how headspace was explained to us at GM A School in the Coast Guard many years ago. Super easy to understand.

Just a mild add on to Ian’s info. You’re less likely to jam into the lands rather than you don’t get into battery with the case keeping the bolt back on the shoulder (or in straight walls like 9mm the neck) which can cause an OOB explosion. Too much headspace grows your brass and separates the head from the neck effectively rendering the gun dead in combat. Last thing with that gap is the worse case head separation where the case isn’t in the chamber up to the solid head during the bullet being in the barrel which is extra nasty. I am a hobby gunsmith and have unfortunately encountered all 3.

Head space in modern weapons is less of a problem than it once was . Weapons using some form of rotating bolt are usually made without any adjustment,relying on the close tolerance of the mating components (M16) it only usually becomes a problem if an aftermarket component is fitted . On weapons where load is taken through a part of the body, there is some form of replicable locking shoulder that can be exchanged for a shoulder of a different size . On bolt action rifles the adjustment is in the threading of the barrel . Change of headspace through just firing is not a problem ,the barrel would be worn out long before there was a change in the headspace.. Bottle necked cases headspace on the shoulder , if the shoulder was so far back as to allow the case neck to contact the rifling , then the firing pin would not reach the primer .

This took me back to my early soldiering and being taught the Browning 30 cal MG. Of course, the lessons there generalised to the M2 later. I formed the “habit” of carrying my own specialised tools, for things like measuring headspace and extracting separated cases. In SVN it was surprising how often and for what purposes my little toolkit came into use, not only for my unit, but other things. I recall getting a chainsaw operative using the kit and fixing range finding radar using parts of the radar toolkit and my own tools.

Excellent explanation. Now I understand headspace a lot better.

That case getting cut in half, that's a new way to fire form 350 Legens right there. Good job.

It's also worth commenting that even with safety measures, an over pressure cartridge can still blow the top off the barrel. An especial concern for hand loaders. After inspection, with any new acquisition that isn't fairly new (like less than 20 years), after thoroughly inspecting the rifle at home and determining it is something I'm comfortable taking to the range, my habit is to fire the first round at waist level and as far off my body as I can get it. Then I very carefully inspect that first case before I fire it again. When I'm confident it isn't going to blow up on me, I'll sit down at the bench but I'll still inspect the next four or five cases and look for changes. I have never had a failure yet (* knock on wood * ) but I have seen a few things that were concerning, mostly about the primer. With those calibers for which I have a number of examples, I obtain gauges to make certain, such as with the Mosin-Nagant collection since those often have substantial wear. because at that point, it's a justifiable expense.

The BREN cleaning kit in the spare parts wallet. Had a ruptured case extractor in it. I never experienced a ruptured case,but it was invaluable and also worked on the LMG and FN L1A1 SLR. In British service.

Good information. I have a 6.5 Arisaka that I thought had a head space issue. My gunsmith determined, after taking a casting of the chamber, that someone had started rechambering it to 6.5x57 and had not completed the process.

Wow, thank you for explaining this so clearly. When in the military I had to conduct headspace checking on my automatic weapon. But to be honest I really didn’t know what or why I was doing it. Now I do! Of course I have not had to do so in many decades, but hey, cool to finally understand why they had us doing it!!

I remember reading somewhere that headspacing problems can be often seen in model 1895 Winchesters chambered in 30-06 because over time that incredibly powerful cartridge can actually compress the bolt's steel. The author of the article highly recommended that headspacing be measured before the gun is shot and before the gun is bought.

Firearm chambers should always be 'de-greased' prior to firing to allow the expanding brass case to properly 'grip' the chamber walls so it doesn't 'slam' onto the breech-face/bolt head, etc. A good reason to thoroughly remove 'case lube' if one is a reloader (nothing to do with headspace, just seems to be a good opportunity to mention it)

Thank you for a very concise explanation of headspace. Most semiautomatic firearms have "timing" that has been set by design--the disconnector won't let the gun fire when the bolt is out of battery. That would be another subject you might explain in a future video. The M16 was designed to run at around 600 rounds per minute in automatic fire mode but switching from cannister powder to ball powder upped the rate to nearly 1000 rounds per minute. This excessive fire rate caused malfunctions until the buffer assembly was beefed up to drop the cyclic rate and some other modifications were made. Older machine guns such as the Maxim needed to be tuned by setting the timing after setting the headspace on a new barrel because 19th Century manufacturing tolerances and anticipated service life of decades and millions of rounds fired were only supportable by making headspace and timing on machine guns adjustable. When the disconnector becomes worn, the gun can fire out of battery--slightly out of battery can be misdiagnosed as a headspace problem when the timing is off due to wear or improper adjustment. Revolvers are prone to timing issues, manifested in the cartridge firing when cylinder and barrel are not fully aligned. That's the adventure of antique firearms--solutions to manufacturing tolerances bring on new problems.

An absolutely excellent explanation of the question in a comprehensible manner. Not only is the content interesting, it is easy to understand. Thank you.

I had a 1903A3 gave to me in 1995 ,I cleaned and swapped the barrel oiled it up all nice took it to my outside range 1st shot 1/2 from bullseye 2nd round didn't hit target at all , I pulled bolt out looked through barrel all clear , checked bolt nothing appeared broken or missing tried 3rd round and it blew up in my face luckily I only had minor injuries ! Then found out a warning was issued on the rifle by serial number for head space! Lesson learned check head space first !!!

Anyone else get that nice warm tingly feeling when someone says "trunnion?"

Here is something I want to add, for those who think they want to check their own. The two terms that get thrown around are "go" and "no go" (come as a set), and you should ignore these. Those are for gunsmiths, and are for setting the headspace for brand new guns only, and are only for setting the initial head space that a NEW gun should have, and is only one end of the range of what a gun can safely use. For users who want to check if their headspace is still within the standards for what is still safe to use, you need "field", not "go" or "no go". Field is the maximum space you can use, as opposed to what a new gun should have, and there is a lot of usable range past "go" and "no go". If "field" closes in the chamber, you have too much headspace, don't shoot the gun. If it won't fit, you are good to go.

In Vietnam we would change a barrel on the fifty by screwing in the new barrel all the way and then backing it off by three clicks. Then we would use use the go no go gauge to get the correct head space. But even then the gun might not fire and eject smoothly so we would just back off another click on the barrel. It’s been fifty four years. I can’t believe I still remember that.

A friend of mine, another Ian as a matter of fact, has been known to say that someone needs to adjust their headspace and timing. This helps me to understand part of that.

On an 8mm Mauser, if the head spacing is incorrect it can blow up in your face. At the end of the war the Allies took the bolts and the rifles from the Mausers surrendered or confiscated and put them in different piles. When a soldier would take one home as a spoil of war they started having problems which led them to take them into skilled gunsmiths to check and modify the headspacing.

Great video. A gunsmith told me that stovepiping with Star B and Super Bs is caused by head space problems caused by wear.

It helps if the gunsmith actually does what he is supposed to. I purchased a Turkish Mauser and took it to a smith. All he did was work the action a few times and said it was fine. Spoiler alert, it wasn't. The spacing was off enough that the rifle wouldn't fire, with factory loads, about 3 times in 10. It was then I read about Go/No Go/Field gages.

One of the best explanations of headspace for the novice that I've seen. It's a commonly misunderstood topic because most explanations are too technical

Thanks for the quick bit of info at the end to give me a rough idea how headspace is set initially. Neat trivia. My milsurp was new old stock pla sks. Wonderful.

303 S&B brass does complimentary case head separations so you too can experience the joys poor head spacing and blown case extraction without the inconvenience of having an actual 303 rifle with sloppy head space.

"What is headspace?" "The reason I don't have an AK bolt carrier halfway through my neck currently"

My father in law had a sporterized m1917 enfield where the bolt didn't fit properly, he got anther bolt thst fit but didn't know to check headspacing. We went shooting and I was testing out my new musket so I wasnt paying too much attention to him. I was standing in the back loading and he was up front firing. Next second I felt something hit my leg, I looked and it was a piece of wood from the enfield, I ran up to him and he slowly turned around to look at me (I have no idea why but he also wasnt wearing eye pro) he looked fine but out of nowhere all of his poors started bleeding. He has microscopic fragmints all throughout his face and eyes but luckily no permanent damage. Please, if you are ever using especially an old gun, research what can go wrong and adress those concerns, as well as always wear eye pro. He says to this day he was thankful it happened to him and not his other son in law that had shot 5 rounds through it before him.

Thank you for clearing that up for me. I had a good general idea about what headspace was. But it's nice to have something like that explained properly for me.

Third example of a modern firearm and the importance of headspace is when you have something capable of shooting multiple rounds IE, ar15s in 5.56. As in you can shoot 2.23 out of a 5.56 gun, but not the other way around. At least I have been told (NRA RIFLE instructor instructor) that that is one of the reasons, the other being that the 556 has more pressure.

You use a go, and no go gauge, to check headspace, the only safe way to tighten FAL rifles is by having rail shoulders welded and ground, on HK fluted barrel systems throw the rifle away it is worn out.. Because HK can only be tightened by welding and grinding the bolt face which gives a false reading with go- no gauges. Symptoms of this is the back of the case tears off leaving part of the case in the chamber so the next round will jam and potentially chainfire the magazine.

The best way to deal with headspace in older firearms, is to reload yourself. There is a trick for seating the round, accounting for percussion, which will fire form the case, to chamber, eliminating headspace on all cases. From personal experience, our brass performed similarly to that of modern rifles, in both performance and load cycles. The specific rifle was a LE Mk4N2, in 303 British. If your interested, DM me, as I'm happy to go through methodology etc..

Very important for fully auto weapons, always check their head spacing and redo it from time to time. I assume, if you reload, you mic your cases, which may indicate a problem before you get stoppages.

Good diagrams. You did better with a ballpoint than many broadcasters do with high budget computer graphics.

Thank you for this video! I watched your video on the Browning M2 and got a lot of question marks over my head when you started talking about adjusting the head space.

Excellent discussion. Also, your voice is pleasant on the ears, your precise way of speaking is great.

Excessive backspace is anything over .004". One layer of Scotch tape is .002" so .004" looks like a small gap. What causes case head separation is the ejector pin pushing the case forward until the case shoulder stops at the chamber shoulder. When you fire the rifle the case head isn't against the bolt face. I don't think I'll ever fire another rifle unless I check the backspace. No-go gauges are pretty cheap.

WOW the artwork at 2.16 should be on display at the NY Metrpolitan art museum