[Dutchman]

A simple representation of a headspace gauge for 8x58RD.

Suggestions are welcome.

Dutchman

 

[kriggevaer]

Very interesting design. Will it be necessary to mill in an extractor relief for the rolling block rifles or does it make any difference? Taking off the extractor and pulling the firing pin on K-J rifles is easy to do, so there wouldn't be any problems there.

 

[AMMOe]

Why are you bothering with anything other than he flanged disc representing the rim? I make them using a similar flanged disc with a simple "O" ring for alignment. I remove the extractor before measurement. Unless I am going to measure a lot of guns, I've found that hardened steel isn't always necessary. I have turned many light-duty units from cold rolled. If I do want to harden it, I use water hardening drill rod. ~Andy

 

[Baribal]

Dutchman's pattern seems to be more axed on the CIP side of a headspace gauge.

SAAMI have different ways to check the headspace, but it is not as precise as the CIP way;

Many times you take headspace (with US go/ field / no-go gauge) on typical CIP calibers, let's say a 8X57 IS and/ or a 6.5X55 SE that will show "advanced field" or even no-go.

Because CIp takes in count more datas, it makes it more precise and if you check the same firearms with CIP standards, they will pass the test easily.

For that reason, I must say I like Dutchman's way of doing things.

 

[AMMOe]

Sorry, but a rimmed cartridge headspaces on the rim. It is the only valid headspacing measurement. The drawing attached only shows a support area on the neck and the rim thickness. I am saying that the support area on the neck is superfluous. ~Andy

 

[Baribal]

CIP standard gauges are;

BR/1 - General shape
BR/2 - Lenght L3 - Dia H2
BR/3 - Shoulder cone - L1/P2, L2/H1

etc, etc, etc...... and goes on .....

From CIP Annex 1, rev. 00-06-06

Maybe should you get a CIP standard book.... It is way more precise than any SAAMI standards....

If the gauge only means to measure the flange headspace, I agree, but to proper check a chamber, nothing comes to the heel of the CIP standard gauges.... On such old guns (and "obscured ammos) everyone should proceed a chamber cast. There is no gain in not doing so.

 

[AMMOe]

I agree if you wish to check the entire chamber, you should cast it. It's the prudent thing to do. I do it with every surplus rifle I plan to shoot. Once done, it is what it is. The safety of the arm will depend on the rim (or "flange" if you refer to it as such) for a rimmed cartridge. This is where all the support comes from.

If you look at the drawing supplied, the only dimension that is has a specified "tolerance" is the rim thickness dimension. (the important part!) Everything else could not exist and the gage would still function as it should. ~Andy

 

[Dutchman]

Its true that the neck pilot isn't needed. It *is* just a preliminary conceptual drawing. I may well eliminate the neck pilot when I make it. I may actually try it both ways to see which has better function.

As for the extractor-- I'd have to study a rifle and see if the extractor retracts below the rim recess sufficiently that it wouldn't interfere with the gauging. I'm thinking it won't interfere on the 1867. On the 1889 I'll check. The firing pin possibly interfering with closing of the breechblock would be eliminated by using a centerdrill in the base of the gauge to provide clearance.

I appreciate the ideas and feedback.

Dutchman

 

[Baribal]

The way I saw it was that Dutchman wanted to make it an complete specs gauge, wich is quite looking like his drawing.
Such a gauge makes a check on every important dimensions at once.
Dutchman, if you have access to a lathe, you should make your gauge with the tolerances from the CIP. It is quite easy to adapt since it is not made for only one caliber, but standardized with + - tolerances.

 

[AMMOe]

I'm not trying to raise hackles here but the post does say "Shop Made Headspace gage..." and then asks for suggestions. I have made many headspace gages and was offering my observations.... which I have done and will do no more. ~Andy

 

[Ordtech]

Andy, they're not beating you up, just saying that Baribal prefers a gauge that takes more measurements into account. Dutchman is sharing an idea, not condemning anything. I've been happy with a button and cerrosafe until now but never felt a button alone was enough. Dutchman is pursuing the safety aspect, and yes, he is fastidious. Back to the topic:

Dutchman, as to the gauge: Since it is on a shaft with a threaded end, have you considered making an adjustable shoulder to measure depth instead of multiple gauges for that? If it adjusts, you won't need as many gauges. Just seams obvious to me. Hey, there's no black eye smilie anymore!
Dennis

 

[AMMOe]

I realize that. I was just trying to make sure that folks here don't think I'm a hard a**. My thing is this. Safety is regulated by the headspace in a rimmed cartridge. A Cerrosafe cast will do the job of any other gages when it comes to the exact dimensions of that chamber. That's all.~Andy

 

[Dutchman]

Dutchman, as to the gauge: Since it is on a shaft with a threaded end, have you considered making an adjustable shoulder to measure depth instead of multiple gauges for that?

hello Dennis

I am of the opinion that adjustable things get out of adjustment and that they usually do so at inopportune times. I do own a 12x36" lathe so making a 3 or 4 piece set is not a big deal. In the end I may well take Andy's advise and just use a simple rim gauge. The neck pilot was thought to be a prudent idea in order to ensure critial alignment but I may have been having crainial flatulence at the time. Bouncing ideas around is a good way to finalize a design. Simple is usually better.

As to oil hardening tool steel as opposed to water hardening.

I have a bunch of Starrett oil hardening chrome-vanadium tool steel in sizes from 1/8" round to 1" round and a bunch of rectangle and square sizes. Did some swapping a couple decades ago and ended up with 100 lbs of the Starrett 01. Its good stuff even in the annealed state so I tend to think of 01 when such applications come up. But it is also true as Andy says that 1018 carbon steel would work every dang bit as good in a home shop where it won't get banged around and nicked or burred. I believe some of the aftermarket throat erosion and muzzle gauges are left soft so as to not wear on a rifle barrel, though I'm a little dubious of that notion. You'd have to be sitting there daily shoving your throat erosion gauge in the breech end for it to hurt anything. Though from what I've seen of those heathen Garandophiles they probably do just that.

Dutchman

 

[kriggevaer]

Well, I think all of you have some good ideas about headspace and chamber measurement, and obviously some seasoned experience, so I appreciate the information. What Dutchman is doing should have been done a long time ago, but after a brief flurry of interest 40 years ago the 8x58RD was simply forgotten, until the last few years when the Swedish rollers started entering the market in relatively great numbers. There should be technical documentation in all three countries about the development, testing, and finalization of the cartridge. I know Rubin of Swiss firearms fame helped in a part of the development of the 8x58RD. Unfortunately there was a terrible explosion at the Hærens Laboratorium in København in the 1890s and many records may have been destroyed. The Nazi occupation of Denmark really stripped the country of K-J rifles, so even after the war the Danes had to rely on the Allies contributions and the use of the captured German Mausers.

Anyway, I'm glad to see Dutchman doing this and I will gladly volunteer to field test the prototype gauges whatever their final configuration.

Now, if we could just get some reliable pressure data -

 

[Dutchman]

The 28,000/29,000 psi as recommended maximum load level in the old Norma reloading data may be the best we get and as bullet weight & velocities for the known samples of factory ammunition support this general neighbhood I'm content for the time being to use this figure above as max for 8x58RD in rolling blocks. Its not beyond reason to think this figure is the one to adhere to. Its certainly not too high.

And concerning Accurate Powder in Montana and the ballistician, Johan Loubser, I did receive from him today a reply to the note I sent concerning his recommendation of load data to a person of this forum (much thanks!) that was grossly excessive based upon erroneous data and current CIP maximum chamber pressure for 8x58RD. Johan assured me that Accurate would "immediately" adjust their load data recommendation for 8x58RD to split the load data into two catagories with the lower one being the application for the 1889 Swedish rolling block using the chamber pressure data from Norma as a maximum recommendation. This is an excellent step with this situation. I explained to Johan that I was walking the ragged edge of what knowledge I have in this area. The support of you all in this has helped more than you know. Its not a lone crusade. I have a feeling I'll be learning far more than I could possibly imagine during the course of this all. This 8x58RD thing is becoming very fascinating to me. I'm going to review Hatcher's Notebook in the next week to bone up on what information I can glean from it about chamber pressure and the like.

Galen - anytime you see me make an error in figures or assumption I hope you won't hesitate to let me know. This goes for anybody else, too.

Dutchman

 

[kriggevaer]

Dutchman, I agree on the 28,000 psi "best educated guess that we can make at this time". At least for the m/67-89 rifles. When we look at similar rifles of that period with known pressure limits based on some repeatable type of testing with reliable instrumentation, we can extrapolate ranges of pressure that are safe in guns of good condition without flaws in the metal.
With a combination of testing with one of the excellent internal ballistics computer programs and the relatively inexpensive piezo strain gauges available now, we could develop a set of loading parameters that are known with certainty.
I have been looking at the RSI strain gauge setup and would love to glue sensors all over my rolling blocks to see what I can find. Since my funds are limited for that stuff, I've also been writing to the various companies and manufacturers trying to get someone interested in testing the cartridge to develop that knowledge. H.P. White labs used to test loads for individuals (or so I've been told), but I don't know the cost or if they will still do it. Need to find that out.
Dutchman with your knowledge of metalworking what are the possibilities of making a pressure test barrel? Then there would be a permanent fixture with bullet trap and permanently affixed sensors. No need to depend on the old rifles and fiddling around at the range when the weather is good. It could even be set up in a basement or a workshop. I know some of the die and reamer makers have chamber drawings that they will sell to individuals.
Wouldn't that be some setup! Load up a batch of test cartridges at the reloading bench, walk over to your own pressure test barrel, fire away, and then start analyzing the pressure curves and readings on the laptop computer sitting on the bench. I think it is do-able.

 

[Baribal]

Andy,

My first choice goes for a chamber cast!. But regarding the use of headspace gauge, for such "obscure" calibers and "unknown" or "in the dark" chamber condition, I do really prefer, and it's my own personal choice, to use at least, a shoulder locating gauge together with the rim headspace gauge. On pre-1920 (about that, it's not sutck in concrete and also depends on who was the manufacturer) the chambers are often longer than what they should, and base diameter is, quite often bigger than what it should be. This comes from my personal experience of older firearms, and you'll never see me shooting such a firearm before a chamber cast....

Regarding the pressure, since it's very hard to get the truth regarding pressure, we can only speculate about that. Pressure is not a simple thing in a gun; it depends on bore diameter, throat lenght, chamber measurement etc.... If let's say Norma says their loads are at XXXX bar (or PSI) they already added (generally 15%) extra to their data. So, you should never base your load on the velocity they announce; 1500 fps in their test rifle for XXXX pressure might be the same as 1275 fps in yours... for the same pressure. Also, and it's a personal choice, that's why I genrally keep my reloads, for older guns at no more than 85% of the maximum announced load, even if no pressure signs are presents.