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... :(