Receiver Measurements
 

When fake crests or dates are put on Luger receivers, I suspect that it would be necessary to remove the original date or crest, etc.

And this would involve the removal of some of the metal from the original surface of the top of the receiver where the barrel is screwed in. Thus the modified surface should result in a measurement that is slightly less than what is the case for a factory original piece.

I have seen a few photographs of Lugers which appear to have a slightly flat receiver surface which may have been the result of a minute amount of metal removal.

Precise measurements could be done, for example, by a machinist with a micrometer, measuring the distance from the bottom of the frame to the top "dead center" of the receiver.

Has anyone ever tried taking precise measurements this way?

Ron,

I believe Dwight Gruber and/or Gerben "vlim" have these recorded.

Ron

I know this has been discussed, unsure if measurements on many has been taken.

My gut feelings:

1. That there are differences in original manufacturing, enough so so that it is hard to tell if messed with.
2. It appears to me that differences are so slight that it would be hard to tell, but you could, to make a date disappear you would have to take off some hudnredths of an inch. And to make crown N dissappear, again measurable.


Ed

... :eek: ...

Post deleted because Ron is right and said it better than I did... :p

(Besides, I had it wrong and now I'm embarrassed!!!) :rolleyes:

Not trying to be a wise guy, but .100" is a "tenth", a "hundredth" would be .010 and would be less than 1/64".

Since you guys are engineer types and I'm a cop type (so don't know this stuff), how deep would a date stamping be?


Ed

...That may explain why my last barrel didn't turn out exactly the way I thought it would... :o

Well, since I've already stuck my foot in my mouth, a little more can't hurt...I'd guess ten-thousandths ( .010" )...I have a receiver with a date on it and it had some pits...so I used emery cloth to take out the pits...and about half the date is gone...Didn't take too much to get down to the base of the pitting...

Ron probably is...I'm just a blue collar worker... :D

It would be difficult to measure the depth of the stamping...because the metal around the stamp is displaced; raised slightly; making accurate measurement difficult...

One point: We all think in thousandths...Hundredths and even tenths are not common terms in the manufacturing/machine tools world...

For example...if you have a sheet of lined notebook paper, like schoolchildren use...it's ~.004" thick (four thousandths)...You'll never hear anyone say "About half a hundredth"...

Despite the fact that different manufacturers dimensions vary slightly, the differences would HAVE to be within the acceptable TOLERANCE for product acceptance. These tolerances are spelled out on the Blueprint CD that I sell. A variation in dimensions which falls outside these tolerances would mostly likely have occured AFTER manufacture, and AFTER acceptance by the government.

Anyone interested in owning a copy of the Luger Blueprint CD can find the ordering instructions in the "sticky" post at the top of the for sale forum.

I am wondering whether it might be possible to detect altered chambers in this manner.

I get the impression that German Luger manufacturing tolerances were quite rigid within certain parameters.

It ought to be possible to measure the chamber surface and compare it to known authentic examples, to detect whether it has had some of the surface removed.

In other words, with some experience, it might be possible to identify boosted Lugers in this manner.

Just a thought.

OK. I looked at the print for the receiver; it shows the chamber hood to base (other side) as 22.3mm = .877"...I don't know enough German to find the tolerance for that measurement...(There seems to be more than one tolerance on this part)...

But I miked my 5 receivers, and got these measurements...

comm, 86434: "A"--.872"; "B"--0.966"
1937, 3649: "A"--.885; "B"--.976" [S/42]
comm, 6782n: "A"--.878"; "B"--.972"
Finn?, 77z: "A"--.873"; "B"--.965"
1917, 8514: "A"--.874"; "B"--.970"

This only shows that this measurement is probably not the best to use for comparison...Although it is the easiest to measure... :(

Hi Postino -

You are definitely on the right track! I was hoping you would jump in on this topic since you are a machinist.

Now if I understand your measurements, of the five receivers you miked, the variation in the measurements from the thickest to the narrowest is only .084 of an inch. Right?

Now each one of these measurements is valuable, because it shows what was created at a certain time and for a certain purpose.

For example, suppose that someone shows up with a 1914 DWM LP08.

You have already shown that a typical Imperial Luger will have a measurement of .875 inch. (And you don't have to use inches, but for purposes of this discussion that's what we'll use.) Now if someone took a 1915, or 1916, or 1917 DWM and ground the date off somehow, it would have to remove some of the original metal and it would have to result in a reduced measurement too. Then the date 1914 would have to be stamped on it. In this example, regardless of how professionally the actual date was removed, and regardless of how professionally the new 1914 date was applied, you would still have a receiver measurement that was below what is "normal."

And this in combination with other factors, would be an aid to determining whether the gun had been boosted or was a fake, etc.

And the value of this technique might not be limited to just changed dates either. Any Luger which had a controversial crest applied to the receiver would be a candidate for this measurement, etc.

If someone is already using this measurement to evaluate Lugers, then I would be interested in hearing more about their experiences.

It would take someone like Postino who knows how to use a micrometer and has the patience to track down and record the measurements before we could begin to draw some conclusions. You would want to take a sufficient number of measurements so that you could have some confidence in the averages for a particular year, etc.

Unless someone is already doing this, then at this point it is just an idea that has yet to be developed.

Maybe this would be a good project to request data from others who are proficient with micrometers, or at least have micrometers--it's not that hard to do. You could then build a data base and perhaps key the measurements to particular variations. We all don't have the drawings, so if you can, post a drawing showing exactly where to measure. Interested?

Well, if as Ron Smith as suggested, Dwight Gruber and/or Gerben "vlim" have recorded some of these measurements, we probably should check with them first before we proceed.

I am sure I am not the only one who is interested in this data and if one of the Admistrators was willing, and if Dwight or Vlim were willing to share it, then it could even be posted as a "sticky" to this Forum.

Does this sound feasible?

Uh, no...(Hopefully, Ron will double-check me on this :rolleyes: )...It's only .013" of an inch variance from least to largest... :)

.885" [largest] minus .872" [smallest] equals .013"

How 'bout a pic showing where I measured??? ;)

"A" is the measurements in post # 12 above...

"B" are these measurements, taken from the barrel hood to the bottom of the receiver lug...

comm, 86434: "A"--.872"; "B"--0.966"
1937, 3649: "A"--.885; "B"--.976" [S/42]
comm, 6782n: "A"--.878"; "B"--.972"
Finn?, 77z: "A"--.873"; "B"--.965"
1917, 8514: "A"--.874"; "B"--.970"

This is a better area of measurement; I believe the lug is held to higher tolerances than that area under the hood...

...And the "B" variance from least to most is only .011"...

I used a Starrett dial verniers for this little test...here's pic of my measuring...

Hi,

Well, I did measure quite some bits and pieces, but I must admit I never measured the chamber height. The idea and initial results are interesting though.

I have several 1" micrometers (well, who doesn't? ;) ) but I prefer the dial verniers...they're easier to use... :p

If anyone is going to make up a database for these measurements, I'll do a better job with my 5...Serial # link to measurements at least...and measure 5 times & take the average...

Now...Why would anyone grind anything off the chamber hood??? I thought the idea of faking was to *add* characters to the receiver...crossed rifle, skull & bones, any date to a commercial...

What would you grind off??? A year date??? Why???

I don't think whipping out a mic at a gun show and measuring a Luger is a good idea...It's sure to get ugly...and will draw a crowd like blood draws sharks...Even if the guy you're talking to is agreeable, the guy two tables over with a boosted Luger will complain about it... :(

The difference in value of a 1914 DWM LP08 to any other date LP08 is at least $10,000. The date could be filled by welding it. Then filed/sanded down to the original surface. Welding is commonly used to fill pits during a restoration. Measuring the chamber height wouldn't matter in this case.

Postino -

When it comes to math, there are really only three kinds of people: Those who are good at it, and those who are not. I have no idea of how I arrived at a figure of .084 differences for your first set of figures. I see how it should have been .014.

Yes, I agree your second set of measurements are more reliable. And thank you for the picture of how and where the measurements were taken too.

With the variance of only .009 it is initially difficult to imagine that the removal of a date or a crest (for example) could not be detected in this manner.

The people who create Lugers to deliberately fool and defraud collectors do not always use high end examples to do it. Instead, they often buy up the junk and "shooter" examples, and it is these that they transform into highly desirable collectable examples.

So our effort to collect measurements does not (in my opinion) need to focus on the high end guns. Instead, it needs to focus on collecting measurements for the ordinary examples. And we can sort them by year and type.

There are already other ways to create an uproar at a gun show. Pull out your jeweler's loupe to look at a Luger. Ask if you can take it apart and look at the serial numbers. Ask if you can cycle some dummy cartridges through it, etc. Personally, I would only be concerned if a seller or dealer refuses to let you verify that what he is selling is authentic. If someone had a problem with you or I taking a reciever measurement, I would think it is time to walk away from their table. Know what I mean?

A few questions: Where did you get your Starrett dial vernier? Would that be the one you would recommend for a novice like me? Would Brownells be a good source?

Vlim - Once we feel like we have got this project beyond the conceptual stage and are actually collecting data, I would like to involve gunboards too.

Thank you!

I would tend to agree. Even if a date stamp was only .010" deep, it would still likely be outside the specs if it was removed...but remember to measure off the stamp itself, as the edges of the stamp will raise up...

Sounds cool. I'm in. :thumbup:

Those will arouse interest surely; as people will assume you are "on to something", and will linger to see what it is...but pulling out a mic and measuring the chamber hood can only mean that you suspect a fake...Danger Will Robinson!!! :eek:

I got my dial verniers some 28+ years ago; one like this will cost you ~$100 now...Mitutoyo makes good tools, too...as do Brown & Sharp, etc...I'd stay away from Sears...I'd check out eBay for a Starrett, as machinists are always upgrading (that's how I got this one!)...

I buy my tooling from Travers online; they send out a 3" thick catalog to me once a year. They list both Starrett and Mitutoyo...

But remember I am old-fashioned; I stick to what I learned with many years ago...Nowadays you can get digital readout verniers that eliminate any chance of your getting the main reading wrong (it happens)...

As I commented, I have mics...but if you are measuring a beautifully blued finish, then a mic may scratch that finish...You 'drag' a mic's anvil across the piece to be measured...and it takes a [very] little practice to get the tension "just right"...

I do know that Brownell's has verniers for reloading; I don't know how precise they are...

Postino -

Thanks for the advice on verniers.

I'm away now for Thanksgiving; however, when I get back, I'm going to buy a good vernier and will get back to you with measurements for the 8 or 10 Lugers I own. I have some cheap verniers, but for something like this I want to be as precise as possible and don't mind spending some money to get a good one.

I think while we are at it, we probably should keep track of serial numbers too. It may be better to keep track of them now then to have collected data and then realize too late that we wish we had kept serial numbers too.

MFC - Mike: Short-wave ultra violet light can be used to detect differences in patination in certain materials such as stone. This is not the same as Long-wave ultra violet light or "blacklight." And short-wave ultra violet light can also damage your eyes if you expose them directly to it. I have not had an opportunity to try this yet on a "suspicious" Luger; however, I suspect that short-wave ultra violet light will indeed reveal the use of welding to fill in a stamped date or a proof mark or modified crest, etc. I have and use these lights. Eventually I need to find someone who has a receiver that they would be willing to have me look at in this manner but for now Postino and I are just going to collect measurements.

Thank you for your insights.

I am wondering if you could "pad" the jaws of the caliper with thin electricians tape to preclude any possibility of scratching the gun, and then "zero out" the caliper before taking the measurements? I would not think that the tape would compress enough to affect the measurement. Just a thought.

Ron -

I would think that would only be a problem with a micrometer, not the caliper/vernier...The caliper/vernier will "zoom" in and out with thumb pressure on the travel wheel and you can read it while holding it against the receiver without moving it...while the mic needs to be moved in & out to get an accurate read...

A bit off topic, but here's another tipoff that someone has altered a serial...This is my Russian capture P38...You can see that the edge of the grip frame shows correct mill cutter tool marks, while the end of the slide and the base of the barrel show a fine ground surface...Someone has very painstakingly ground off a very shallow portion of these two surfaces...almost certainly to stamp the new serial...which is stamped very shallowly also...

BTW...Since some of us are cops, truckdrivers, accountants, and gourmet chefs...Here's a pic of a couple tools I use...my dial caliper (also called a dial vernier), two 1" micrometers, and a machinists spirit level (degree gradations are on other side)...The Brownie mic was my dads; the silver one I got at a flea market basically for pocket change...The mics are dusty and somewhat "patina'ed" from not being used for...decades...because of the dial vernier/caliper...The machinists level I got off eBay; I use it for installing barrels and front sights...

The micrometers work just like a "C" clamp; you hold the anvil against the work and twist the barrel down until the spindle hits the other side of the work...and slide it back and forth just putting very slight pressure against the work......

The dial caliper you can just push the jaws against the work and read the dial...and then release the jaws...

Disclaimer:...I am not a great machinist...At times I am a good machinist...Mostly I am a "good enough!" machinist... :p

(As in "Good enough for government work!") :D

Gentlemen:
My measurements are as follows:

"G" date, 7158a: "A"--0.875"; "B"--0.969".

BYF42, 3732f: "A"--0.871"; "B"--0.968".

Neil Young

OK: I went back and re-measured all five of mine...This time I made sure I was *not* measuring across a date, or a number on the lug, or across a dent or ding...and I got several different measurements...so the letters/numbers and any dings or dents will affect the accuracy of the measurements... :(

I also made sure I was as close as perpendicular to the horizontal plane as possible...I noticed that if I went just a bit off 90º that the measurement would change... :rolleyes:

The receivers are "fatter" on the sides than on the top/bottom...So the least measurement will be 90º from horizontal...or straight up & down...That's the one we want...

Neil Young - Thank you for the measurements. I've added them to our list.

QUESTION: Is there any member of this Forum who has education and experience as an OPERATIONS RESEARCH ANALYST?

If so, please send me a private message on this Forum, and I will explain what role you can play in this effort. Thank you!

:rolleyes: Just turned 73 today and my old brain gets kinda fuzzy at times, but if I remember correctly, the DWM "alphabet commercial" Lugers were made from war time Lugers, and the date was removed from the top of the reciever by DWM. If you look at one of them from the muzzle, you can see where the top of the receiver is thinner than on a dated Luger. I haven't measured one, and the receiver still stands proud of the bbl flange, but it definitely has a "flatter" contour than the dated guns.

So, couldn't you compare the measurements of an alphabet commercial to a dated Luger to determine how much metal has to be removed to remove the date?:cool:

Hugh, good idea.

A measurement of the depth of a typical year marking compared to the receiver thickness.

Hugh -

HAPPY BIRTHDAY!

Excellent idea. Thank you.