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I am still at a bit of a loss as to how headspace is determined when & after cutting a chamber. How do you know how deep to cut the chamber in order for the barrel to screw into exactly the right headspace position ? Do you cut to nearly where the chamber should be then screw in the barrel & check then remove & continue & repeat till you get it right ? I`m told that some chambers are cut while already screwed into the action, is this true? so many questions I know, but this is really getting to me. I`m about halfway through Roy Dunlaps fine book "Gunsmithing". I just can`t seem to find it written exactly how to start from scratch with a barrel blank, an action & a reamer. Thanks in advance for any responses. Cheers Morton If it sounds too good to be true, It usually is ! | ||
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I chamber the barrel depth by eye until I get to within 1/8 inch of proper depth. I then install the go-gage in the action and screw that to the barrel and measure the distance between the barrel shoulder and front of the action with calipers and as I'm within a 1/32 inch I use a feeler gage. | |||
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Boy, that sounds real accurate! Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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Morton 3 don't Australia have any gunsmiths ? | |||
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A barrel can be chambered quite easily without removing it from the lathe by using a depth gage to measure the distance between the locked up bolt face and the face of the action. This should be the the length of the barrel tennon. the chamber is then cut to a depth to put the case head at the same plane of the end of the tennon, possibly three or four thou. deeper to accomodate ctgs. that have a slightly longer headspace. This works well on a Rem. and Stolle action and I think the rest of them. Bob | |||
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Well, then tell us how you do it.  | |||
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Yeah Concho, There`s a handful of them around. But I want to start myself. My previous gunsmith is retired, so I`m left with finding another or becoming an amatuer one myself. I understand the principle of the process but not the practice of it. The depth of chamber in relation to the length of the barrel thread. It is the barrel thread that governs headspce as far as I can understand, i.e how do I know how deep to cut the chamber if the thread is a constant length ? It appears I`ll probably have to find a gunsmith & ask if he`ll show me how this headspacing business is done. Frustrating stuff. Morton If it sounds too good to be true, It usually is ! | |||
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B Beyer, Thanks I get your description, as long as the thread on the chamber end is referred to as the tennon then I`m with you. To repeat what you`ve said in my words, I measure the distance from bolt face to action face. This distance is my reference for the chamber reaming depth. I ream the chamber to allow a cartridge to protrude from the chamber the same length as the reference length of measurement. (bolt face to action face) I assume I would measure this on the barrel from the shoulder of the barrel back to the cartridge base for this measurement ? Morton If it sounds too good to be true, It usually is ! | |||
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morton, this is not to bust on you, but what you are asking is a pretty involved subject. john hinnant taught a basic rifle barreling course somewhere and has had the textbook he wrote for it published. (brownells inventory #404-100-000). get it and read it and it will clear up alot of questions. it is very basic and assumes you have very little knowledge of machining. i believe it is one of the best publications for a beginner. is it the best way to do the job, is it the only way to do the job; everyone who does this type of work will have their own opinions. what you will discover that at a minimum you will need a lathe with some tooloing, a safe action, a barrel blank,a reamer, a go and no go headspace gauge, action wrench and barrel vise, micrometers and depth micrometers. with the above you also need the knowledge to use them. if you can find a mentor to allow you to watch the job a few times so much the better. everyone develops their own system and procedure to reflect their own beliefs and tooling. some will not use both gauges and some use a specific lot of brass to set headspace. i don't, even though i fully understand headspace. i use specific gauges for the cartridge made by the same manufacturer. america has become a sue society and i would rather explain to the court that i used the available tooling and not how i did the job any other way. after 30 years in law enforcement i am more comfortable sitting at the prosecutors table than the defense table. max | |||
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Morton It almost sounds like you are making it more complicated than it really is. Think of anything fitting just right. Not too long and not to short. Just right. Obviously, if your headspace is too long you won't be able to close the bolt on the cartridge because it will be sticking out too much from the chamber. And if too short the cartridge will have the ability to move about in the chamber. (see below for correction of words) If I am not mistaken, for a hunting rifle you want a few thousands of headspace, but generally not more than about 5-6 thousanths. The best way to measure it with a proper DEPTH Micrometer. And you should have a set of GO and NO GO guages for each cartridge you are going to chamber. Take the distance from the receiver ring to the bolt face and subtract from it the barrel shank length (distance from the receiver ring to the inner shoulder). So for example, looking at a 1909 Argentine Mauser action I have here the difference from the action face to the inner shoulder is .630 and the difference from the action face to the bolt face is .745, so if you subtract .630 from .745 you get .115 which would be the amount you would want your go guage to stick out from the end of the barrel for an absolute perfect fit. But there is a crush factor to take into account so you could subtract a couple of thousanths from .115 leaving .113 and then a couple more thansandths for a hunting rifle leaving about .111-.112 as the amount you would want your GO guage to stick out from the barrel. And then, obviously, at that point you should not be able to close the bolt on the NO GO guage. If you can close the bolt on the no go guage you have made the chamber too deep. BOTTOM LINE _ Have an experienced gunsmith show you how to do it before you do it!!!!!!! | |||
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here's a link to a longer post I wrote on CNC cambering, but the process is the same. https://forums.accuratereloading.com/eve/forums/a/tpc/f/...=263105105#263105105 assuming a mauser, you measure to the C ring and to the bolt face, the difference is the distance the headspace gage will stick out at zero. a go to no-go difference is generally .004 or .005. about 1.75 sheets of paper! jeffe opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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I think this is exactly right...only backwards. But that's just my opinion. Too much headspace is sloppy, too little is too tight. The opinion of 10,000 men is of no value if none of them know anything about the subject. - Marcus Aurelius - | |||
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Morton, if you measure from the bolt face to the part of the action that the barrel shoulder butts against and make the tennon the exact same length the tennon should be the right length. Now all you do is chamber so that the ctg, case is exactly even with the action end of the tennon. As I said before a few thou. deeper will not hurt a thing and will leave a bit of chamber space for cases that may be a bit longer than the one that you are using for reference. Blowing cases out a few thou. when fireing doesn't matter at all, I have done this up to .013 and the cases have been great. One thing to remember is that any cases that you use in one barrel should be dedicated to that barrel and not used in another. This will give you your best headspace fit case to chamber that you can get, also a case fired in one chamber may not fit in another chamber. Good Luck. Bob I would use a ctg. case as opposed to a go gage, you don't shoot gages out of your gun and it is the case that you want to fit. Bob | |||
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That advise is both careless and dangerous! Morton3, headspace is something you do not want to guess at. Bob may get by reloading his stretched brass of .013, but some sucker is going to end up with that gun when Bob's dead and gone and they are going to A) have to pay extra money to correct Bob's mistakes, or B) they may stick a slightly over charged round, of the proper dimension, in the "excessively headspaced" chamber and hurt or kill themselves, or, someone else. Don't be a fool by developing bad habits picked up following the advise of some of the crap that is posted here. Find a gunsmith who is willing to explain, or better yet, show you the safe and proper way to set up a chamber.. | |||
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Malm, Check the headspace on some new ctgs. before and after they are fired and then tell me that stretching brass a bit is dangerous. In the first place I did not tell him to go .013 deep, I said a few thou. Like I said check the headspace on some unfired factory ctgs. and again after they are fired, a lot of the factory stuff people shoot every day are stretched more then I am talking about. Bob | |||
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Your right. What I meant to say is that Obviously if your cartridge is sticking out too far you wont' be able to close the bolt and the opposite is that the hole is too deep and the cartridge will have too much space. Thank you for correcting me on my use of words. I knew what I wanted to say but chose the wrong words to say it. AND like I said, and I agree 100 % with Malm who is an expert at chambering, IF YOU DON'T KNOW EXACTLY WHAT YOU ARE DOING, THEN HAVE SOMEBODY WHO KNOWS SHOW YOU SO THAT YOU DON'T BLOW YOUR HEAD OFF. | |||
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Just because things are don't make them right!  Aut vincere aut mori | |||
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The first thing that you want to do is get the RECEIVER to screw on the barrel and then have the BOLT go in and close w/o any pressure or resistance. Doing the calculations for this step will involve some depth measurements and decisions on clearances required. Looking at a take-off barrel helps. Making a short, sample barrel stub is good practice, I make one for each brand of action that I encounter. I use "go" gages and shims that I've cut from .001-.005 thick feeler gage stock. Checking the amount of protrusion of a "go" gage from your die will also give you something to consider when setting the amount of "headspace". Different folks have different definitions of "headspace". | |||
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It is precisely because the possibility exists to obtain brass cases that are somewhat undersized, that makes having the weapons headspace correct, all that more critical. Going back to your .013 example, imagine some bubba reading this thread and setting his headspace to a case that was fired in your .013 excess chamber. And he, not knowing it was .013 off while following your advise, gave it a "few" more thousandths clearance. Now picture some poor slob acquiring that rifle at a gunshow (where these guns usually end up) and chambering and firing a cartridge that was just shy of a standard length case. Do you see any problem forming? Headspace is critical for the safe operation of a firearm and is set at the chamber. It requires precision gauges, measuring equipment and procedures to set it correctly. Headspace is set to industry standards which allows the "safe" use of commercially produced ammunition. Chamber dimensions which fall outside of these "set standards" are considered "wildcat" dimensions, and are handled in a completely different manner by handloaders. And the barrels are usually marked to indicate "other than factory" dimensions so someone doesn't kill themselves. Correctly setting the headspace is one aspect of gunsmithing that should never be guessed at, or, compromised. Peoples lives depend on those who assemble guns to get it right. If factory ammunition falls out of spec, and it happens occasionally, then that is an issue for the ammo manufacturer, and should not to be used as an excuse for setting up a potential disaster. | |||
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Malm, I do not consider a chamber that is A COUPLE of thou. longer than a factory piece of brass as a disaster waiting to happen. You will notice that I said that a particular chamber should have dedicated brass for that chamber and no other. I do not shoot a gun that is chambered for a factory ctg. and even if I did that is certainly no excuse for posting something that is dangerous. If a barrel is indicated properly and the chamber is cut with a reamer that is ground to correct size two or three thou. deeper than a piece of factory brass it most certainly will be a lot more accurate than some of the chambers that are cut into the majority of the factory junk that is on the market. You may think differently, and I respect your opinion, but noone will make me believe that it is dangerous. An interesting experiment would be to chamber a barrel with a go gage and chamber one three thou. deep with a piece of new brass and see just which chamber is the deeper. As a go gage has to be long enough to be able to chamber any factory ctg. it would not surprise me if that chamber was deeper than the chamber cut with a piece of new factory brass and 2 or 3 thou deep. I have a go gage for every reamer I own, and havn't used one in quite a while. Checking the shoulder of a group of factory ctgs. would give a good idea of just how long a go gage has to be. I have no factory ammo here, but have access to a gun shop that I can measure different makes of ctgs. I will let you know what I find,unless you have some and can let us know. I am really curious now. Bob | |||
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I just remembered that I have a box of Rem. 30-30 here and measured the headspace of seven or eight of them with the Stony Point H.S. gage. Within the same box the shortest measured 3.466 and the longest was 3.472. Thats a difference of .006 within the same box of ctgs. I will still check some different ctgs. and let you know what I find. I really do not think that the 2 or 3 thou. that I add to chamber length is going to blow anything up. Bob Bob | |||
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Uh, the 30-30 headspaces off the rim. | |||
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I certainly realize the 30-30 headspaces off the rim, but that space between the case shoulder and chamber has to be filled by something.I also have some unfired 6BR brass that I will check. Lapua 6 BR brass, same lot, same box, measures from 3.135 to 3.139 measuring about a doz. of them. As I say, I have read a lot of your posts on here and respect your opinion, but after the first fireing of these cases in my chambers, they surely fit a lot better than the junk you buy in a gun shop. I have cases that have been fired over 25 times without ever being F.L. sized, or having the shoulder bumped, and they still win an occasional HBR match. Bob | |||
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b beyer: would you mind terribly if I asked you to post the serial numbers on all of the rifles you have chambered. I am sure there are a few of us who would want to know so we can steer clear of them.  Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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That is called fireforming. Fireforming is relatively safe provided the headspace is within spec. In the case of the 30-30, the brass moves forward from where it is headspaced, with a rimless case, the brass moves back and then out to fill the chamber. On a rimless chamber that is cut excessivly deep, the brass stretches back to the bolt face, exposing the thin area ahead of the web where the pressures cause the case to rupture and send hot gas and pieces of brass back into the shooters face and into the magazine. | |||
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This is not to make anybody produce rifles with excessiv headspace, but a litle expirience acheeved after handeling more than 15000 former militaryrifles, as well as civil productions. My expirience is that to create a safetyissue, you have to make the headspace verry big, actualy so big that the rifle most likly will klick before(unless with a clawextractor) To big headspace main problem is poor accuracy, and problems with lifetime of brass when reloaded fullsized down to min. length. When checking varius diferent brands of rifles you will find that the unsupported part of the brass varys from 2.5 to 4.5mm. Tests performed shows that CRF rifles in standard (not belted magnums) calibers has a tendency to let go of the casehead with mutch lower preasure, than a pushfeed action, likly because of the mutch better enclosure and support of the brass, on a pushfeed bolt. I ame not writing this to make anybody produce rifles with to big headspace. A pretty simple way to adjust headspace is: 1: Make the treads 2. Cut a chamber with apx the same length of the case sticking out, as on the original barrel 3: put a go gauge in the chamber, and close the bolt, and then screw in the barrel. If the barrel stops before tightening to the flange of the reciever, then make an clockwise marking on both barrel and reciever, then open the bolt, and tighten the barrel the rest. By checking how big a part of a rev you can tighten further, and by knowing the lead of the thread, you can calculate how mutch deeper you should chamber. But the easiest way is to cut the chamber a little to deep, then install the barrel, put in a gogauge, and then try to put 1-2-3-4-5 layers of paper in the boltface, while testing when the bolt becomes hard to close. When this happens you just take out the paper, and mesure the total thickness of the compressed paper. Then you have a pretty excact indication, of how mutch you should turn of the flanche of the barrel to get an excact headspace. To check if heasdspaces is within acceptable, you can use a gogauge, to check if you can close, and if you put 1 pcs of writingpaper in the boltface then you should not be able to close the bolt without resistance. If you dont have a proper headspacegauge, you can perform the same test with a factoryloaded case and up to 2 pices of paper | |||
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Jorgen I wish your company would make a good quality Mauser 98 action in three different lengths for a reasonable price. How about that? | |||
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I've always found it easier to cut the chamber properly the first time. Cut it to .0015" or .002" deep depending on how much you torque the barrel. Then when it is cinched up tightly, you end up with zero (excess) headspace. | |||
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Poleax, if you crushfit .002, you are using a 6 foot cheater pipe and torguing the action. 60lb-ft is all one needs, and that's on the stiff end. cut to .0005 to .001 "deep" if you like, going past that, and wanting "zero" you are bending stuff. .000 headspace is ONLY preferable on a benchrest gun... .002 is considered standard.. closes on a go, don't get even barely started on a no-go. jeffe opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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Heiffer, I can assure you I do not use a 6 foot cheater pipe. I use a one foot wrench, snug it up, and give it a very scientific "bump". A mere eight degrees rotation is all that is required to achieve .002" crush. I cannot recall when I have "bent" anything during barrel installation. Although, I'm fixin to tell you to get that way. I'll install my barrels my way and you do yours like, well everything else you do...... Given the variances in brass mostly leaning toward too small, I am perfectly comfortable with my method. I have yet to have a factory round, or any other for that matter, that would not easily chamber. Tell us again how those yugo intermediate bolts work as-is in Sr Mexican 98 actions? | |||
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Mark Stratton taught a .002 crush also and I never saw any 6 foot bars or anything twisted out of shape. | |||
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When I calculate final headspace, I ALWAYS allow .002 for crush. And I don't use a cheater bar. | |||
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What a fantastic quote... .002 is on the FAR end of tolerance,and I would never install a barrel that sloppy... Do what you want, it's your barrels. jeffe opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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great answer. opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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Jeffe
Jeffe
So which one is it? This thread is doomed to be deleted if you keep going like this. | |||
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Chic, I admire your tenacity... .002 HEADSPACE is not .002 crush. Pretty basic stuff, aint it? Normal headspace is about .002 WITH THE BARREL INSTALLED.. .000 is a benchrest tactic. next gunsmithing lession has a perhour charge. Doomed to be deleted? Why, because a stockman (and an amazing one you actually are) doesn't understand installing a barrel. No biggie, but probably best not to worry on it. opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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Wicked crush??? I have a great respect for Marks ability and teaching and can not say the same about you. And get over what? | |||
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Chic, .000 headspace is after the barrel is installed.. a benchrest tactic.. .002 crush, achieving an underminded (it's immaterial) headspace is, well, sloppy. and the two are only marginally related. You are probably one of the best stockmen in the county, and I would look to your advice there. Thanks for the personal insults again, attacking my business and materially harming me. You will be following your own advice exactly when? jeffe opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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What a fantastic quote... .002 is on the FAR end of tolerance,and I would never install a barrel that sloppy... Do what you want, it's your barrels. Jeffe, What is your problem? When did I say anything about .002"? I happen to install my barrels so the bolt JUST closes on the go gauge. I too chamber .0015" deep and snug my barrel up. When installed without the assistance of a gorilla or cheater pipe using my wimpy little arms the bolt just closes on the gauge. Would you care to elaborate on that cryptic remark of yours? I find it amusing as hell that as the moderator you start more "fights" than you quell. Aut vincere aut mori | |||
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z1r i agreed with your quote, and didn't mention you being sloppy. No fight with you, no intention of one. .0015 is a pretty tight cinch, .002 is HUGE. So, if you are excited about me saying you said .002 about anything, then that's a misunderstanding. I didn't. no fight at all. opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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