I understand the two concepts.

I was not insulting your business, I giving an opinion on the issue of the crush and the advice of a well established metalsmith versus yours. I suspect that you are doing a good enough job yourself harming your business an need no help from me. My comment, if you take the time to read it was in regard to respect of your ablities. Now you need to remember the quote about finding yourself in a whole .......... time to stop digging.

quote:

Originally posted by jeffeosso:
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

Jeff,

None of my rifles are built as benchrest guns. they are all hunting rifles with the exception of one heavy barreled silhouette rifle I made.

I take issue with your assertion that achieving essentially zero clearance on the go gauge is sloppy. Rather I think it speaks to the ability of the person installing the barrel to take careful measurements, make careful cuts on the lathe, and calculate the appropriate measurements required.

I think the only one hurting your business is you. You say one thing in one post then contradict yourself in another.

I'm beginning to think the only opinion you value is your own. You care not for the accumulated knowledge other's bring to the forum, especially if it surpases your own.

quote:

Originally posted by jeffeosso:
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.

Jeffe,

Perhaps you wish to teach me something. What Poleax said is exactly right. If you want your chamber to have .000 headspace, then to get that .000 headspace, you must cut the chamber approximately .002 deeper than needed. In order to get the .002 headspace that you say is average, you would need to cut the chamber .004 too deep. Do you see a pattern here? Where should I send the invoice? Schools out!

You know, things might go a lot smoother here if you would simply take a minute and re-read what you write prior to hitting the send key. Draw yourself a picture if you need to in order to make sure understand what is written. And then when someone calls you on your error, quit digging your hole by making up stuff.

Whats the big deal here. Everybody calling everyone else names and making accusations over 2 thousands of an inch. I could see it if you were talking about your sex organs, but headspace? come on guys.

For all practical, normal installations, when the barrel is in place, the bolt goes down on the go-gauge and stops on the no-go-gauge. What is needed for BR is another story, but for a normal hunting rifle, this is all good. If gauges are not available, two sheets of paper on a factory round does the job.

Malm explains this very well...

quote:

If you want your chamber to have .000 headspace, then to get that .000 headspace, you must cut the chamber approximately .002 deeper than needed. In order to get the .002 headspace that you say is average, you would need to cut the chamber .004 too deep.

I totally agree, if you want .002 crush fit, this is perfectly correct. and if you want .001 crush fit, change .002 to .001 and it's again perfect.

The only time *I* would, without a customer requesting it, set for ZERO, is on a bench gun... even in a hunter class.

I expect the .002 headpsace Chic mentions from Mark (though I haven't spoken to either gentleman in the matter) is the final headspace, which is a pretty DANG good place to be for an accurate rifle that might consome factory ammo.

Where I differ in Malm's statement is the ammount of crush. I have read Malm's machining skills, and he sounds like an excellent machinist. He faces the actions, cuts very tight threads, and even goes so far as to, on mauser, torque off both the shoulder and the inner flange. It takes a fantastic machinist to delever this on a rifle, and I think he probably does an excellent job.

I would imagine his threads are perfect 55deg, as he's stated before, and a pretty snug fit, I believe he's stated he likes a class 3a or 3b fit.

And it is exactly this type of quality work that makes me feel, rather strongly, that crushing this class of work .002 is a negative.


So,
if you want a zero headspaced rifle, with an amazing tightly threaded barrel, I believe Malm is your man. Sounds like he does excellent work, and has done quite a bunch of them.

I don't believe that .002 crush (not headspace, let's not get confused with terms)to get final headspace is required, and should be considered the far end of tolerance. It is past tolerance in my shop, but that's my perogative.

jeffe

quote:

Originally posted by jeffeosso:
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

You know what, On re-reading this (thanks for the suggestion Malm) I can see where this may have come over negatively.

Sorry, meant to to be more along the lines of "Well, dang, I wouldn't get near .002 crush if I could help it"...

I may not have been perfectly clear is deliniating between crush (in thou) and final headspace (in thou) .. I thought the paragraphs that started on each would have been clear enough. thanks, I'll try harder, next time, to be perfectly clear.

Righto,

I`ve started this thread & I`m sorry to each & every one of you blokes who`ve offered opinions or methods on how you do it & subsequently been criticised by others .

That was not my intention here & I`m sure nobody else intended to get into this debate in such a strong manner.

That said, I`ve read on a bit more of Roy Dunlaps book & discovered he recommends to chamber the standard sporting rifle chucked in the lathe with the receiver screwed on.
Hopefully using the old barrel as a template for the new barrel thread profile, length, TPI etc etc.

Now I`ve gotta say this makes a shitload more sense to me now. Dunlap advises roughing out most of the chamber metal then simply using a stop collar on the finisher reamer when getting to within 1/16" of correct depth. Then clean chamber check with go gauge, cut a bit more & so on till within 10 - 20 thou & finish off to the required depth by hand.

I am a fitter/machinist by trade & own 2 lathes & a vertical mill & understand most of the operations performed by these machines. I am now in the process of making a barrel vise & action spanner similar to those pictured in Dunlaps book to suit a Czech built M98.
I have an old Omark .308 target barrel which I was hoping to rechamber to 7.62x39 as my first project.
The parts I`m using are used, inexpensive & cheap to replace. I must also do work on the bolt face & extractor & a few other things.

If I stuff it up, I`ll start all over again until I get the headspace right

Before anyone blows up about this method, remember I am just learning about this & have decided to approach an older gunsmith I`ve heard of to possibly show the operation in the flesh. I think it was 22WRF suggested this also.

OMJ probably is correct in saying there might be different views on headspace tolerances.
That is really the beauty of this forum, the enourmous amount of information & experience just a question away.

I love reading the different views, sure it can be confusing at the start but what isn`t when your learning.

I know a couple of you blokes were critical of B Beyer & his method but he was the first to get the idea through to me, so for turning on the light bulb I thank him.

Once again thankyou for your replies
I have a much better understanding now than when I posted the thread .

Cheers Morton

Morton

The book you are reading is a good one. But see if you can get your hands on a copy of the book entitled The Gun Digest Book of Riflesmithing by Jack Mitchell. If you are going to start fooling around with Guns its a nice book to own with a lot of good material in it.

For a hunting rifle that is to be released to the general public, The proper opperation of SAMMI tolerance gauges that are correct for the given caliber is THE STANDARD. Negateing the extra .002 of chamber depth will negate the full function of a SAMMI gauge set when the barrel is tight with the action. M-70s need this extra .002 as there is no interal breeching ring and they tend to crush,seat more than a Mauser, same with a Remy and others of likeness,
plus a 16 vs a 12 tpi thread is going to enable the wrench opperator to crank that action on further, which is another thing to take into consideration. I always try the gauges with the barrel still in the machine, I just gentley snug up the action and see how the feel, it give a general referance of how it will be when the barrel is tight to the action. I always use a dab of lubriplate white grease on the threads and mateing sufaces as well before the frist tightening, that just seems like the right thing to do and a good fitting thread with some good grease on it is oh so nice.

PS. The size differance from the major on the thread to the major on the shoulder will also affect how much crush,seating is going to take place upon tightening, I prefer a 1.2 on a 1.0 thread, bigger shoulder more rigid, only makes sense. You'll notice a factory M-70 is 1.155 on a 1.0 thread major seems a bit chincy.
Timan

Why do some of the knowledgable people on here say that there is a different headspace set up for a hunting gun and a benchrest gun. Other than a reamer that is a bit tighter and a tight neck I do not see why. Once a piece of brass is fired in a chamber, that brass SHOULD be a perfect fit for that chamber whatever the chamber is. I chamber 30 cal. barrels with four different reamers, a 30X47, a 30BR, a.308 and a ctg. that I made up myself. I am really curious as to what I may be doing wrong as all of these barrels are used in HBR guns.

quote:

I`ve started this thread & I`m sorry to each & every one of you blokes who`ve offered opinions or methods on how you do it & subsequently been criticised by others thumbdown.

That was not my intention here & I`m sure nobody else intended to get into this debate in such a strong manner.

One just needs to learn to avoid the sunday night drinkers that trash the smithing forum.

I formerly posted my method of gaging headspace and can assure you that it's been a sound and accurate way for me of measuring headspace prior to tightening the barrel to the receiver.

I try to ream .001 to .002 deeper than the go gage and after tightening the barrel the go gage goes and the no go don't even start.

I agree with those that chambering to anything other than the standard gages is not being of service as some may think. Very little if anything is gained by chambering tighter than the go gage.

Seeing some ofthe comments on missing safety on slightly excessive headspach.

Can any of the experts tell me in plain english,
What is the risk??
and when does the risk increas ???

Dont want just hersay, but real tested experience

quote:

Originally posted by duikerman:
I try to ream .001 to .002 deeper than the go gage and after tightening the barrel the go gage goes and the no go don't even start.

Ain't nothing wrong with that...

malm, I realize that this thread has been down the road but I just happened to see a chamber drawing for a 243. The headspace dimentions at the .400 datum line are a min. of 1.330 and a max. of 1.340, a .010 difference. Quite a lot min. to max.

quote:

Originally posted by b beyer:
Why do some of the knowledgable people on here say that there is a different headspace set up for a hunting gun and a benchrest gun. Other than a reamer that is a bit tighter and a tight neck I do not see why. Once a piece of brass is fired in a chamber, that brass SHOULD be a perfect fit for that chamber whatever the chamber is. I chamber 30 cal. barrels with four different reamers, a 30X47, a 30BR, a.308 and a ctg. that I made up myself. I am really curious as to what I may be doing wrong as all of these barrels are used in HBR guns.

All true , Beyer, the only difference between chambering a hunting rifle and a BR-gun is the preferances of the rifles owner. A "sloppy" chamber is not going to ruin the rifles presicion. As long as the brass is not streched to much, no harm is done, they all neck-size the brass anyway.
But, and it is a big but(t), If a gun is delivered to a BR-shooter with a "sloppy" chamber, the smith will never again build a BR-rifle. In a hunting rifle, it is not the end of the world if the bolt does not stop until half way down on the no-go-gauge, but on a BR-gun it would be "catastrofal".

Anyway, I think Jørgen has asked a question that should be answered by those who think he is wrong.

Jorgen, It depends on what YOU call slightly excessive, but what I call slightly excessive [2 to 3 thou.] I feel is as safe as any factory chamber going. This thread was brought back to life when I posted that I had seen a chamber drawing for a .243, where the min. and max. dimention from ctg. base to datum line on shoulder were .010 apart. I do not see how these guys can can say that chambering .002 to .003 deep over an unfired case can be dangerous. I would be willing to bet that a chamber done that way would not have as much excessive headspace as a factory chamber. Look at the numbers and you will see that it is impossible that it is not a shorter chamber. Remember that you are using an unfired case.

quote:

I do not see how these guys can can say that chambering .002 to .003 deep over an unfired case can be dangerous

Assuming a new factory loaded correctly made round is used, it's not and I don't think anyone said it was dangerous!

The point that was made was that since you don't know the dimensions of the cartridge you used then you don't know the next factory rounds you buy will fit the chamber. Further it was discussed that the rifle might become the property of others some day and that person will buy/inherit a potential short chamber and have to pay to have it fixed.

If this practice is used it's far better to chamber to a FL resized case as in this manner the reloaded shell in that set of dies will always fit.

Here's the real kicker however: The benefit of so doing is minimal and just not worth the effort. Use the go-gage and chamber to the minimum and you'll not have to be concerned with the rifle when problems arise.

duikerman, most certainly this was refered to as dangerous by malm in just so many words and a few others by inference. Of the 21 barrels that I am now shooting, not one is chambered for a factory ctg. I make up my own brass out of factory brass and I certainly do know the dimentions of it. I also have dedicated brass for all my barrels, shot in that barrel and no other. They shoot rather well as a matter of fact. With a max to min. difference of .010 I am not too worried about chambering .002 over a min case.

PM sent

quote:

Originally posted by b beyer:
Jorgen, It depends on what YOU call slightly excessive,

I believe it is explained pretty well here:

quote:

Originally posted by jørgen:
This is not to make anybody produce rifles with excessiv headspace, but a litle experience achieved 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 very big, actualy so big that the rifle most likly will click 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 am not writing this to make anybody produce rifles with to big headspace.

Jørgen is not advocating sloppy chambers, he know as well as evereybody how a chamber is supposed to be, he is just aking for proof that this is a safety issue?

As stated earlier, I have deliberatly fired cases that were .013 shorter than the chamber with no ill effect at all. These cases now have something like 15 loadings on them. I do not say this is ideal, just that it can be done.

quote:

Originally posted by b beyer:
Lapua 6 BR brass, same lot, same box, measures from 3.135 to 3.139 measuring about a doz. of them.

You better get rid of that shit! I never heard of a 6BR that had an OAL in excess of 3 inches!

Jim, that is base to datum line measured with a Stony Point H.S. gauge.

Some 60 years ago Julian Hatcher performed, and published, tests with the chambers reamed deeper and deeper to produce excessive headspace, and found no safety issues from that sort of increased headspace. Many shooters in the last 50 years have inadvertently performed a similar test by firing .308 Winchester cartridges in .30-06 rifles. The 1/2" of extra headspace just results in a funny looking fired cartridge case.

"Hatcher's Notebook" is recommended reading on the topic of headspace.

The dangerous sort of increased headspace comes when the space is added not at the front, but at the rear end of the cartridge, due to bolt lug flexion or lug setback. More of the cartridge case protrudes from the chamber, and there may be enough unsupported thin brass in the wall of the case in front of the head to rupture, releasing dangerous amounts of gas into the action.

A shallow-chambered barrel screwed down against a "GO" gauge, though seemingly within allowable headspace tolerance, could produce this dangerous condition.

Headspace is something that requires a little bit of head use to understand. It's not just a matter of measuring for a single number in a certain range. And being out of the recommended range doesn't necessarily produce a dangerous condition.

hello Ricochet
Finaly sombody actualy trying to put some facts and testresults on the table.(instead of sounding like a preacher in churtch on a sunday )
The headspaceisue is according to your refered tests, just as i stated earlier

According to the protrution from the chamber, ther can also be diferent opinions wether it increase or reduce safety.

There are two lines of theory.
1:by increase the protrution you lower the point where the case lets go, as you said because of thinner walls. Some manufactures look at it as a sort of safetyvalve, giving you a nasty, but not leathal expierience. Instead of letting the preasure rise until the lugs let goe.

2: Making just enough protrution, to let the extractor catch. Making ´the actions and lugs mutch stronger to be able to handle a mutch higher preasure.
This wil limit the amount of blowups, but when the mutch fewer happens they mighe be more dangerous, especialy if the enclosing of the case is strong enough to contain enough preasure to rip of the lugs, or split the reciever.

As i said earlier there are manufactures using protrution from 2,5mm up to 4,5mm (0.1" up to 0.177") And i would not call anny of them idiots. Just constructers with diferent way of evaluating safety

Given those two choices I'll pick #2 every time. I don't want to trust to the vagaries of brass strength and construction from different ammo companies to determine whether I'm going to have a "nasty, but not lethal, experience," and a case head blowout doesn't seem like a good "safety valve" to me. Letting too much brass protrude unsupported at the rear increases the likelihood of a significant accident. I'd be quite upset if I had a blowout that did nothing more than pop out the magazine floorplate.

quote:

Originally posted by Ricochet:
Given those two choices I'll pick #2 every time. I don't want to trust to the vagaries of brass strength and construction from different ammo companies to determine whether I'm going to have a "nasty, but not lethal, experience," and a case head blowout doesn't seem like a good "safety valve" to me. Letting too much brass protrude unsupported at the rear increases the likelihood of a significant accident. I'd be quite upset if I had a blowout that did nothing more than pop out the magazine floorplate.

To keep you awake a litle longer.(if you are a CRF fan)
I can inform you that tests with the same caliber and the same lot of brass, showed that a CRF action with a head protrution og 2,5mm let go of the brass at the same preasure as a PF action with 4,5mm of head protrution. the tests was performed with new Norma brass in caliber 6,5x55 and they both had a caseheadrupture at estimated presure of 82.000 psi.
while a PF action with 3mm of head protrution let go at 132.000 psi, almost riping of the lugs and the support for the lugs.

Due to tecnical problems mesuring that kind of preasure, the estimats was calculated by using LOAD FROM A DISC.

The estimat was wery near to results of static thrust tests

I never realized that any of these actions had that much unsupported case. I know the actions that I use have right around .005

Without sectioning and measuring the cases being used, and comparing that with a cross section of the action, I don't know whether the 2.5mm vs. 4.5mm protrusion made a lot of difference in the exposure of unsupported thin brass. I'm not an advocate of CRF vs. PF actions, and I do believe that some PF actions better surround and support the case head than a CRF action can, but certainly many rifles of both sorts have a long record of performing well. I'm not knocking CRF actions, either. I love my Mausers. The test you mentioned could reflect a situation where the protruding case head was completely surrounded by the bolt of the PF action, which is not the case with a typical CRF action. I'm not sure how the CRF vs. PF issue got inserted into this discussion, but it's another example of what I meant that headspace is not a simple, cut and dried issue of measuring for a particular number, and concluding whether it's safe or not from that. A rifle is a system that has to be analyzed in its entirety to understand where potential safety issues may exist.