View Full Version : Headspace
March 18, 2008, 08:34 PM
I'm not sure where to ask this question about the term Headspace. What does it mean? I read up on it alittle and kinda know what they are talking about, but why is it so important? do you need to know this if your reloading, and do i have to worry about it on my 1911 45 and AR-15 223. I'm new to this, so help please
March 18, 2008, 10:41 PM
I posted this on the other forum where you asked the question. Headspace is important because if the cartridge does not fit the chamber correctly you could damage your firearm and yourself.
What is Headspace?
by Walt Kuleck
For those of us who are relatively ignorant and/or inexperienced as gunsmiths, could you be "technical" for a bit about the subject? What exactly is headspace? Where is it? What are the tolerances, etc?
There are two ways to look at headspace. First, let's consider the practical definition, and follow up with the technical one.
In practical terms, headspace is the clearance allowed between the base of the cartridge case and the face of the bolt. The position of the cartridge in the chamber is controlled in a variety of ways depending on the type of cartridge case involved. Most rimless automatic pistol cartridges (e.g., 9x19mm Parabellum, .45 ACP) are positioned by the case mouth resting on the front edge of the chamber. Rimmed cartridges (e.g., .45 Colt, .30/30 Winchester) are positioned in the chamber by the face of the rim resting on the rim recess at the back of the chamber. Belted magnum cases (e.g., .300 Win Mag., .458 Win Mag.) are positioned by the belt resting on the recess provided for it at the rear of the chamber, much as rimmed cartridges are. Finally, bottle necked rimless cartridges are positioned by the shoulder of the case resting against the shoulder of the chamber.
So when a cartridge is chambered, it is positioned in one of the above ways. Once positioned, there must be a little free space between the cartridge case base and the face of the bolt, to allow for dimensional tolerances in cases. When the cartridge is fired, the case expands in all directions, including toward the bolt face. If there is the intended clearance space, the case head is not stretched excessively during this expansion. If the space is too much, as the case head is pushed backwards towards the bolt face it may stretch enough for it to significantly weaken the case in the area just in front of the thick portion of the case head, called the web, where the thinner walls of the powder containing part of the case begin. If the case head does not separate on the first firing, the weakened brass may do so on subsequent firing. This is a very bad thing, as hot gas at 50,000 psi will damage at least the stock and magazine, if not the firer's hands or face. Little drops of molten brass and brass shards are carried by the hot gas at near-supersonic speeds. If all the firer gets is a Chicken Pox-like tattoo, he or she is fortunate.
March 18, 2008, 11:17 PM
Thanks for explaining. So for 45 ACP does the bullet depth in the chamber effect the head space. Is it something to check when reloading a new round for the first time. what I'm trying to figure out is what causes the round to not be the right distance. Is it just wear over time on the gun?
March 19, 2008, 07:18 AM
Depending on the shoulder of the bullet it might. I taper crimp my .45s to .472 and that seems to be the magic number for me. Headspace will change more commonly in a rifle rather than a pistol; higher pressures, more powder, etc. equals more errosion and change to the chamber, but it would take lots and lots of rounds to do that.
You can check your .45s by taking the barrel out of the pistol and dropping one of your loaded rounds in. It should be level with the back of the chamber. If too high or too low, you need to adjust something.
March 29, 2008, 07:32 PM
First CDRT thank you for your service to our country.
I just wanted to say I've never found a 45 acp case within specified length.
March 30, 2008, 09:12 PM
Just to clear up one point. Headspace increase in a rifle is NOT normally a result of chamber wear, it is the result of the wear and battering of the bolt locking lugs and the corresponding lug seats in the receiver. That wear and battering takes place to a very small extent with every shot, and those "small" increments can eventually add up to excess headspace and trouble.
The same thing happens with a locked breech pistol. On the M1911 type, the battering takes place in the barrel lugs and slide recesses; other pistol types have the same problem in other ways.
Even a revolver can develop excess headspace as recoil causes battering of the ratchet and other parts; what some folks call "endshake" is really excess headspace. In extreme cases, with hot loads, the revolver top strap can stretch and also cause excess headspace.
April 2, 2008, 07:00 PM
The headspace check given above is not correct, it's even misinforming.
April 3, 2008, 03:21 PM
I don't believe I'd want to try to correct Jim on headspace - I don't think Jim needs any correction.
Lug, set-back, and the other things he's mentioned are quite correct. Chamber wear - i've never heard of it happeing and if it occurs it would after so many rounds the rifling would be gone. headspace is caused by a multitude of issues all of which jim understans perfectly.
Jim is the only smith I've ever heard mention and explain "thread timing" a very technical issue. There are few other smiths who even know what it is.
When I'm confused on an issue I usually ask jim for clarification.
I am sure posts people write are not written with distrespect for Jim. Just wanted to put my 2 cents in.:)
April 3, 2008, 08:34 PM
Thanks for the kind words, Harry. I confess it took me some time, even after I had installed barrels, reamed, etc., to understand exactly what headspace is, why it exists, and what can happen if it is not within specs. But in this case, I am not sure the comment was directed to me. For another thing, there seems to be some confusion about terms; one poster may have used the term "bullet" when he actually meant "cartridge."
Another area of confusion is the 1911 pistol. Some people insist that since the cartridge case is straight and can slide back under pressure, there is no need to worry about headspace. That, of course, is not true. Others think rifles used with rimmed cases like the .303 British can't have headspace problems if the case is only neck sized and the shoulder is allowed to contact the chamber shoulder. Again, not true.
Gauges are not infallible either and can lead to false confidence. I recall one rifle that the owner had a "gunsmith" rebarrel. Either the guy didn't know how to use a reamer or didn't have one, so when the cartridge failed to seat by 1/8" or so, he simply ground the difference off the back of the locking lugs! The headspace gauged fine, but of course a whole lot of case was totally unsupported by the chamber. Fortunately, the owner thought the gun "looked funny" and brought it to us before firing it. He didn't like what we told and showed him, but I never read about a gunsmith being shot, so I guess they worked something out.
April 4, 2008, 07:16 PM
Lugs being ground to correct ?????. My God. how can anybody be so stupid?
It's like a Jap a guy showed me the brass that had been fired in it 7.7 Jap! The only problem was someone had chambered it to 30-06. Yes he's still alive - but the Jap brass was ruptured and the primer smeared all over the case head - a whole box of it!!!!!:eek:
April 5, 2008, 12:55 PM
...the Jap brass was ruptured and the primer smeared all over the case head - a whole box of it!!!!
The first one should have been an 'Oh ****!'.
Good thing must guns are well over designed.
April 6, 2008, 08:39 PM
Harry, there are some pretty dumb folks out there playing gunsmith. I see quite a few posts here and elsewhere that begin "I want to be a gunsmith, what do I need besides an FFL?" A little knowledge and experience, maybe?
Objectively, it is silly that we require training and passing an examination to be a beautician, but none at all to be a gunsmith, when getting a bad haircut has never hurt anyone.
Still, no one is out to ban haircuts or bad dye jobs, so some paranoia is understandable.
April 14, 2008, 10:25 AM
Harry (and everybody else),
Read Frank de Haas' "Bolt action rifles".
He's got a nice story on this topic.
Makes great reading with lots of information.
April 14, 2008, 01:50 PM
I have been a outside machinist,Boilermaker,welder,Pipe fitter,utility mechanic to multi craft in nuclear Submarines to ultra modern chemical plants.Went to machinist school to learn to measure,relate to and be able to draw a working print that a machine shop could use to make a destroyed part from.Learned the basic operations of the Machinist trade tools.In my preteen years I also helped out to learn with a old gunsmith who restored museums and collectors firearms in the 50's.I got to see,touch and even fire a few of the guns we all hear,read and dream about.My pay was in learning and shooting with reduced loads for this kid.Relate to?I got to touch and even shoot the guns I saw in the pirate and western movies!Mr Olstein,at 62 I still remember and love you!
It was known that I collected Cheap old Military guns.Even tinkered with such miner jobs as I was "Qualified and had the mechanical experience" to do.I was not a GUN SMITH and recognized the fact.I have had a unbelievable number of guns brought to me wanting me to correct their blunders that they made "Saving money".Most were destroyed as a decent or even working firearm.My "Gun smithing" jobs have all been limited to previously disabled "Wall Hangers" or garbage headed guns.It is the only firearm to practice on.Many folks want to sell the butchered job they did to some one else at a most premium price with out regard to it's safety.Most but not all home gun smithing Trigger Jobs that I have personally looked at and checked were DANGEROUS in my opinion.Now this is from a guy who has a double trigger German set trigger on a custom Kleinguenther Mauser action set for 3 lbs.and then 3 oz.on the set when ordered.My Ruger Super Blackhawk trigger is super sweet.I ain't against a "proper" trigger job.Now when I started loosing the feeling in my hands I adjusted both triggers in my rifle way up to shoot as long as I was able.Recoil could possibly kill me now as it was not only painful but caused me unbelievable bruising and internal bleeding.
Another personal peeve is the "Home Gunsmith" who buys a cheap gun of any type,spends two to five times the money "Bubbaing" it out and then actually gets offended if you won't buy this "Valuable customized firearm at "his" appraised value.As long as he was happy,great.I am happy for him.It is when he gets unhappy and wants you to pay a premium price for something that is junk to you is when I get offended.Half of these "premium guns"would have had better care and be in better condition had they gone to"Hell and Back"with Audi Murphy during WW2 and that is the truth.
I may be wrong but I believe that a quarter of a million dollars would have to be a going out of business real good deal to start off with the tools and machinery needed to be a Master Gunsmith with a almost complete shop "if" you had the skills.I say almost as any craftsman never has all of the tools they would like to have.
The majority of the folks who I have seen proclaim their selves "Gunsmiths did not even know the names of most of the Gunsmiths tools they used and some did not have as many tools as I carry in my vehicle as a "breakdown box".I know,I asked.If they didn't know or did not want to answer my questions about their knowledge and qualifications,I walked out and told every one I knew.This brag I once encountered when asking about tools were,"I got two different kinds of screw drivers"."I got a big and a little un in each size".He was serious.I had gone to school with him and knew him.He was a simple slow Honest as the day is long GOOD MAN trying to make a living.He believed he was good!I would have gladly used him if I thought I could.
The ones that got it ain't ashamed of what they know or don't know or the tools and skills that they do not have.They will gladly send your firearm off to ones who specialize or have a expensive specialized tool.There are some good local gunsmiths.A Gunsmith will recognize his limits,whether skills or tools.The butchers don't.The best do not know everything,but the butchers always do beforehand.They also have all of the excuses down pat.
My opinions are from 50+ years of "Gunsmiths" while living in different areas of the country.My purpose is not to ridicule these folk as THEY THINK & BELIEVE that they are gunsmiths.I went through 4 years of on the job training and various State accredited night schools to be and stay a mechanic as times change.I loved Guns but did not have the money or the time with a family to learn to be a Gunsmith.
I AIN'T DEAD AND I AIN'T QUITTING.alfred
April 14, 2008, 04:31 PM
I think the quarter million is pretty close to the investment one would need for a well equipped gunsmithing business, and it might even be too low. Most of the people on these sites who want to be gunsmiths are good folks, and some have mechanical skills, but few have any idea of the investment required for even starting out. You can farm out stuff, but eventually customers figure out that they don't need you as a middleman and take their business to the guy who does your work.
Even simple tools, like a barrel vise and receiver wrench, with the most common bushings, will easily run $400. (No, a pipe wrench is NOT a good idea!) Chambering reamer sets run well over $150 for the common sizes, more for special order. And hell hath no fury like a customer who is asked to share the cost of that special .37 caliber barrel and the reamer for the .37-600 wildcat he dreamed up. He wants you to foot the bill for the special order!
In brief, an FFL, two screwdrivers and a mill bastard file are NOT enough to set up in business as a gunsmith.
In addition, as I say so damned often people get tired of it, learn how to run a business. Any business man faces hundreds of laws, rules and regulations, pitfalls and problems, even if he is selling beanbags. Anyone selling or repairing guns has more laws and rules to comply with and a vastly increased danger of lawsuits. Insurance alone will take a big chunk out of your gross profits! If you think it is all a matter of taking in $20 and figuring you made $20, you have rude awakening coming.
April 14, 2008, 04:49 PM
I saw "Chamber wear" mentioned in some of the above post.I have a .22 rf. mentioned in another post with a loose feeling spot in the barrel though it shoots great.This gun has the original old barrel,stock and peep sights of a Remington 510P.The receiver,bolt trigger and all working parts look brand new and looks to be added later.It is a single shot like the 510X.The chamber looks to be sleeved because of a very thin faintly noticeable circle around the chamber.The chamber seems to be the same as My Ruger SS 10-22T Factory target barrel.As I said before,I could not ask for a better shooting gun.it is not drill/tapped for a scope but the peep sight gives great accuracy.Do they bush 22 chambers?I see no indication of barrel bushing from the muzzle end.
I also saw where the Jap.7.7 was chambered to a 30-06.I have a "ground" one in "good"shape.The shells are so expensive and the neck turning involved to convert 30-06 to 7.7 is a pain.I was wondering about the 30-06 conversion "If" you have a tight enough barrel.How much work and expense involved?All of my pill bottles with my slugs and measurements disappeared in a house cleaning in anticipation of my croaking so I would have to check it again.Some folk ain't got the common decency to wait for you to die to start getting rid of "your garbage" so I treaded them as they treated me.I didn't have the common decency to die!
Also,could the chamber cartridge neck area be reamed a few thousands to eliminate the 30-06 brass neck turning when converting the brass to 7.7 without making it dangerous "IF" someone fired the correct 7.7 Jap cartridge in it?
All opinions and experience would be appreciated.
I AIN'T DEAD AND I AIN'T QUITTING.alfred
April 14, 2008, 05:16 PM
Jim.I personally think that if you find a good honorable,honest Gunsmith,you are better off letting him do the farming out of anything that he can't do.You then have a expert to know who to send it to,get with the others and discuss the wanted and needed work.He will check out the work when completed and make sure it was done right before returning it to you.This is well worth the small percentage or fee you will be charged.I also believe that it will be far cheaper in the long run.If something ain't right,he is there to represent you.Sooner or later,it won't be right or what you expected.Also the good men in the trade know far more about the quality of the work the specialist do than you ever will.I believe this saves you money and gives you a better quality of work.
Knowing what you can do means knowing your limits.You cannot have one without the other.Some never learn this.
I AIN'T DEAD AND I AIN'T QUITTING.alfred
April 14, 2008, 07:26 PM
Sir, you are an ORIGINAL, I like your cut, You.
are far from CROAKED and will be for years = I.m sure glad you're on the forum with us,
There isn't much more I can say. except I love you. you old salt - it sounds like you;ve been there and back and probably seen the elephant many times,
Keep on truckin buddy.
April 22, 2008, 04:43 PM
Harry,I saw the Elephant at the tender age of 7 at the Atlanta Zoo.I ran off from the rest of the family to share my popcorn with a Elephant.She wanted it all.I was strong trunked up against the bars and dropped my popcorn.She released me and snared every bit of my popcorn.How many Elephants rob kids?How many kids get robed by Elephants?She was a pro.She behaved perfectly when my parents were present and my brother and sister fed her a little of their popcorn.Being I was in trouble for running off,I could not tell my parents.I for one believe that not only are Eliphants smart,they are capable of and do commit robberies!
Yep.I have seen the Elephant.
I AIN'T DEAD AND I AIN'T QUITTING.alfred
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