Mauser headspace

[Swiend]

Hello all, I have a simple question regarding headspace. I have a previously bubba'd Czech mauser in 8mm. I later found the receiver to be somewhat bent and bought a used one from Tradex.
I have since installed my barrel onto the new to me receiver and checked the headspace using 2 different methods and it looks like I have a difference of .010"
Is this excessive?
Any help would be appreciated.

 

[guntech]

I am assuming the 10 thou is headspace not just a difference. If you used steel headspace gauges, 10 thou is slightly excessive.

How did you measure it?

 

[Potashminer]

For an 8x57JS cartridge, there is a standard dimension - normally determined using a GO gauge (minimum length) and a FIELD gauge (maximum accepted length for continued service). Some barrel makers mention a "NOGO" gauge which is supposed to be a standard of maximum length for a new installation. Is pretty much black and white - either longer than GO and shorter than FIELD, or not. Anything else is non-compliance.

Non-compliance does not mean it won't work - I have several rifles that do not likely comply - in many cases, because there are no standards for them anymore, if there ever were any. So I have to fit the brass to that chamber. But any SAAMI or CIP compliant ammo can be safely chambered and fired in any SAAMI or CIP (respectively) compliant chamber. If you use something different to establish your headspace, you are sort of out there on your own.

It can get "wild and wooly" - for example the Swede military armoury used a gauge set for 6.5x55 that is longer than the same set by SAAMI. So, often, a brand-new-from-Swede-Arsenal chamber will "fail" a SAAMI gauge test. Swedes were making 6.5x55 since about early 1890's. SAAMI did not exist until 1920's. Go with whomever you chose, I guess...

 

[Swiend]

I asked my local gunsmith and he would have charged a one hour minimum of 75$ to check the headspace but told me he would use the "shimming " method as he doesn't have the correct gauges.
So what I did was take a full length sized brass and pressed a new bullet to act as a dummy round.
One method I used was to lightly engage a spent primer into the pocket, chamber the round and then compare the differences in length.
The other was was to take the same dummy round and add a layer of aluminum duct tape to the base of the brass. After 4 layers the bolt was very hard to close. Both methods gave a .010" gap, for lack of a better term.

 

[Potashminer]

Both methods that you used relied on some standard length for the brass case that you used. At least repeat with 2 or 3 from several boxes of brass - do not expect all will give same results. For many, what you did might be "good enough" - but a real headspace check is done with steel ground gauges that are accurate to the much less than .001". Up to you what is "good enough" for what you are trying to accomplish.

 

[Potashminer]

As far as "shimming" - you can do the same - buy an $8 feeler gauge set - can cut less than .5" circles - set the circles on bolt face or brass case - use a slight dab of grease as "glue" - then try to close bolt. Look up standards - is common to see a minimum length and a maximum length for your cartridge - maybe can assume that your brass is longer than minimum - up to you to decide how much is "too much" shim. If I take a .006" shim behind a GO gauge and bolt won't close, I can tell you that chamber and bolt is less than .006" from GO. And that a FIELD gauge, for that cartridge might be .012" from GO. Again, up to you what it is you are trying to accomplish. You have to look up exact min and max numbers for your cartridge to know.

By the way - a bullet has exactly "zero" to do with head space - is all about the fit of the brass case (assuming a rimless shouldered case) into the chamber.

 

[guntech]

You haven't measured anything as far as headspace is concerned.

I suggest you don't use your local gunsmith as he doesn't have a steel go gauge and can't measure headspace either...

Finding someone with a steel go gauge or buying one will be the first step in measuring your headspace.

Next to that would be buying a box or two of commercial factory ammo (not military surplus) and using that compare those rounds to your chamber. You still are not measuring headspace though... or correcting it if excessive...

You need a gunsmith...

You can full length size a brass and prime it... and fire it... the primer will back out roughly the amount of headspace the rifle has... measure that protrusion.

Ideally a full length sized case with no bullet... you should be able to just feel the bolt closing on it at the bottom of the bolt throw... you need to use a stripped bolt to do this...

 

[Swiend]

I do intend to verify the headspace either with proper gauges or an equipped gunsmith before firing this rifle. I appreciate all of the input as well. I hope to have this rifle ready for hunting season with a clean bill of health, lol.

 

[MattE93]

Do you have access to any other smiths? Some in my town charge a full hour for headspace. One very lovely shop does it for free. I’d call around

 

[trevj]

Do you have access to any other smiths? Some in my town charge a full hour for headspace. One very lovely shop does it for free. I’d call around

I'd figure the one that does this for free likely makes back the money in good customer relations.

 

[guntech]

You can safely shoot it with reloads that are made to fit it... first size a case up so the neck is larger - creating a case that will not chamber due to the large diameter neck ... then set your sizing die to just size the case enough so the false shoulder you will create when sizing this neck hits the chamber and holds the case back against the bolt face when the bolt closes... This works so much better than seating a bullet out to engage the rifling to hold the case back... this method fails most of the time...

 

[billdick]

You can safely shoot it with reloads that are made to fit it... first size a case up so the neck is larger - creating a case that will not chamber due to the large diameter neck ... then set your sizing die to just size the case enough so the false shoulder you will create when sizing this neck hits the chamber and holds the case back against the bolt face when the bolt closes... This works so much better than seating a bullet out to engage the rifling to hold the case back... this method fails most of the time...

This is exactly how I load for a lot of my old stuff and for any wildcat I put together that needs a shoulder change. Works very well, just need to keep your brass and dies set for this rifle only.

 

[Potashminer]

OP - I have been using a copy of SAAMI standards from 2015. SAAMI did not invent the 8x57 cartridge, but they publish standards for it and call it an 8mm Mauser - is NOT the name the cartridge is called in Europe. If you are buying North American made ammo - like Remington or Winchester or Federal - it likely says "8mm Mauser". Even PPU from Europe makes those loads and uses the 8mm Mauser name - it is ammo loaded to SAAMI's specs. If you find ammo labelled 8x57JS - that is CIP's name for it in Europe. They allow a much higher pressure than does SAAMI. So for same weight of bullet, the 8x57JS (European stuff) is going to be several hundred feet per second faster than SAAMI 8mm Mauser - although the brass case and bullet are exactly the same.

Looking at the 2015 SAAMI chamber drawing for 8mm Mauser, they are showing a minimum and a maximum length. So that will be from the closed bolt's face to a reference point along the chamber shoulder. There is .010" difference. So the way SAAMI compliance works, your commercial North American made ammo will be SAAMI compliant - meaning it will fit into the shortest SAAMI sized chamber. And will still fire safely if put into the longest SAAMI compliant chamber. So SAAMI decided there is .010" difference that they will allow from minimum chamber length to maximum chamber length. A ground steel GO gauge is for measuring that minimum length - should be able to close the bolt as Guntech describes above. If you put a .010"+ shim between that bolt face and the GO gauge, that bolt should NOT close - you are at FIELD gauge length. So if you are not going to use ground SAAMI compliant gauges, sort of up to you to decide if you are somewhere between. Your headspace is "correct" if it is between GO and FIELD length anywhere within that .010" allowance. For safety purposes, there is NO difference between longer than GO and shorter than FIELD - neither you nor the rifle are at any risk. There is some thought that greater accuracy might be possible the closer that you are to GO length, but I suspect quite a few other factors have to also be set in place. There is also some thought that the brass gets "worked" less if closer to GO length, but brass should be sized to match that chamber - regardless of actual length - so I do not understand how brass can be worked "less".

I installed an orphaned barrel into a small ring mauser action - a Peruvian Mauser barrel that was chambered too deeply and had a longer barrel tenon thread than did the 1895 Chilean action - I had to "peel" dimension from that barrel face, and adjust the barrel shoulder by making a "breeching washer". I did not have the GO gauge for the 7.65 Mauser cartridge. So I full length sized 5 cases that were fired in another rifle. And I set that barrel so that I could just so feel the start of "drag" on the bolt's body in the last smidgeon of handle movement as it closed. That bolt will not close at all with a .004" shim. Good enough for what I wanted. Essentially, I was using my full length sized cases as my "gauge". I have no clue if any other brass will fit - no idea if it matches to CIP or SAAMI or anyone - do not care - but I do know that full length sized brass from these dies, do fit. And that is all I really wanted out of it - a way that I can make that thing go "bang"...

 

[Swiend]

Thanks so much for the replies, my "simple" question about headspace has turned out to be anything but. I am feeling a little more confident about firing this rifle, the brass will be carefully scrutinized after each shot.
Something else that I've learned while researching my headspace concerns is that while resizing brass, using a matched shell holder is a good practice. I was using my RCBS dies and my Hornady shell holder thinking that they are all interchangeable. Using my calipers, I got a consistent .110" dimension of the deck height instead of the standard .125". I wonder if that smaller dimension had an affect on the shoulder of the brass or maybe not. I switched back to my RCBS holder for the other half of my reloads.

 

[Potashminer]

I had not read about "matched" shell holder? For many cartridges here, I have RCBS dies with RCBS shell holder. But is also multiple with Lee, Lyman, and other shell holders, and similar brands for dies - some are "matched" - a great number are mixed brands. What you want is concentricity - regardless "matched" brand or not. I would think any shell holder needs to have a bit of "wiggle" so the case can move a smidgeon if it wants to on the trip into the die. And goes to the press ram and shell holder notch - as mentioned, I happen to use RCBS Rockchucker press, but most any brand of shell holder fits, aligns and has been used at one time or another.

Is very possible to use shell holders and get various sized brass. The idea is that there is a "solid" dimension from where the case head sits in that shell holder, then usual RCBS instructions say to have that same shell holder top face contact tightly to bottom of the FL die - many suggest that you get your RCBS press to "cam over" at the top of the stroke to ensure that everything in shell holder, die, and press linkages are "tight" - therefore repeatable. Changing out shell holders part way through a run might change lengths. Repeatability seems to be important for best accuracy - maybe makes no difference at all whether the round goes "bang" or not.

I was re-forming one kind of brass into another. For whatever reason, I felt I needed to get those cases a few thousandths more up into the die. I was not certain that was really the issue, so did not want to permanently alter either the shell holder or the die. I discovered that I could slide a shim from a feeler gauge under the brass case, when it was in the shell holder - I think was .004" or .005" or so. That would have the effect of forcing the case that much further up into the die, without making any other changes. Turned out to not be the issue that I had to resolve, but I did discover that as a way to force a case further into a FL die, than the "normal" set up. I do not own any, but apparently some makers make sets of shell holders to buy that have a series of less height from where the case head sits to the top face of those shell holders. Others suggested that the bottom face of the die could be ground off, to get that case further up in that die. I did not want to buy that shell holder series, and I did not want to permanently alter my die until I had figured out what was needed - the feeler gauge thing let me find out I was making a mistake - as it happened, the "problem" was the 1/16" or so just ahead of the belt was "fatter" in the die, than in the rifle's chamber - had to get a Larry Willis die to solve that one. That was a bit "twisted" because I wanted the case to "headspace" on the chamber shoulder, not on the chamber's recess for the case belt - which was what everything was set up for.

 

[Potashminer]

Thanks so much for the replies, my "simple" question about headspace has turned out to be anything but. I am feeling a little more confident about firing this rifle, the brass will be carefully scrutinized after each shot.
Something else that I've learned while researching my headspace concerns is that while resizing brass, using a matched shell holder is a good practice. I was using my RCBS dies and my Hornady shell holder thinking that they are all interchangeable. Using my calipers, I got a consistent .110" dimension of the deck height instead of the standard .125". I wonder if that smaller dimension had an affect on the shoulder of the brass or maybe not. I switched back to my RCBS holder for the other half of my reloads.

Re-reading this. The bolded part. If you have .015" difference from the ledge where case head sits to the top face, from one shell holder to another - that is more than the difference that SAAMI allows for Min to Max headspace dimension in an 8mm Mauser. If that is correct, that might reflect on the length that the two makers make their sizing dies - which might have lead to the notion of "matching" shell holder to sizing die. I had not heard of this previously.

I had been trustingly loading and firing factory new brass in most of my rifles. Or if previously fired brass, I will use the shell holder that I stow in the box with the sizing die set. After first firing, I set the sizing die by watching the sizing mark work its way down the neck - trying the sized case repeatedly in that rifle. Not unusual to get close, and then bolt will no longer close - I think the case body has now been squeezed smaller a bit and that pushed the case shoulder forward. I continue to tighten down that die until I just so get the brass so that the bolt closes easily. That means to me the die is set for that rifle chamber. I keep my cases separate for each rifle, even the ones that I have multiple. I re-set my die every time, for each rifle. It only takes about two minutes, with practice - no mysteries, that way... That shell holder may or may not be tight to the die, at the top of the ram's stroke - does not matter - that case is now correct length to match that chamber.

 

[Why not?]

You can safely shoot it with reloads that are made to fit it... first size a case up so the neck is larger - creating a case that will not chamber due to the large diameter neck ... then set your sizing die to just size the case enough so the false shoulder you will create when sizing this neck hits the chamber and holds the case back against the bolt face when the bolt closes... This works so much better than seating a bullet out to engage the rifling to hold the case back... this method fails most of the time...

This is by far the most secure way to insure perfect fit of ammunition to chamber. I have done it for at least forty years, and never had a problem with brass life. In fact I discovered it because of case separations that were occurring in a 9.3X62 rifle. No problem when necking up to 40 cal first, and then resizing brass to just barely allow the bolt to close on the case.

Some refer to it as a "crush fit". Easy to do, and 100% effective.
Ted

 

[Potashminer]

I would have to agree completely with Post #17 - that gets your hand loaded ammo to perfectly fit in your chamber. But your chamber might or might not be to a SAAMI or a CIP compliant dimension - but if loading your own, properly, you probably do not care. Only becomes an issue if you are only shooting factory ammo, or at least want that as an option - have to have your chamber to fit to what the ammo factory made - which in North America was likely to SAAMI standard. Commercial guys will build a rifle and chamber it to accept factory ammo - so has to meet their tolerances. Home hand loader is not really constrained by those dimensions - but should be still very much concerned with "fit".

 

[gaff]

The German's, WWII. Considered their rifles safe with up to 13 thou of headspace. reloads or case life was not a concern for them.
depending on how you installed the barrel to start with, and how tight it is on there. would be the starting point for me.

 

[Potashminer]

The German's, WWII. Considered their rifles safe with up to 13 thou of headspace. reloads or case life was not a concern for them.
depending on how you installed the barrel to start with, and how tight it is on there. would be the starting point for me.

I have not been able to find European chamber dimensions or tolerances - so, .013" measured from what?? Or do you mean they allowed .013" from minimum to maximum chamber length? Or do you mean .013" more than their military cartridges were made? So far as I understand from SAAMI drawings - "headspace" is a distance from one point to another - so is something that can be measured - for SAAMI in 8mm Mauser the minimum allowed is 1.8743" from bolt face to the reference diameter on the shoulder - maximum length is .01" longer. Maybe war-time Germany had a different way of expressing it?

Barrel torque - I don't think that has much to do with capacity to handle breech pressure - many 308 Win / 7.62 NATO target rifles (and other chamberings) have barrels that can be unscrewed or re-attached by hand - not really very much torque at all - but different if rifle is used as handle for a bayonet, I think?? I have no experience about it - but I think even just firmly hand tight that a barrel will not "unscrew" when fired? There was something about direction of rotation of rifling, though - equal and opposite effect - British and USA were often opposite directions - CW vs CCW - in one case, the bullet going up the bore tends to "tighten" the barrel thread, in other case, tends to want to "loosen" it.