Loose rails and accuracy

Ron Harding · 11-29-2019, 10:24 AM

Hi. New guy here.

I have a 1938 S/42 VoPo that I bought for occasional shooting. It was rebarreled with a new Canada-legal barrel (don't even get me started...)

Lugers have a reputation for being very accurate pistols. But... I'm having trouble. Shots go all over the place. I get much, much better accuracy from my CZ-75. I've been trying to figure out why. It's all matching-numbers, by the way, not a Franken-Luger.

One thing I've been wondering about: Lugers were supposedly made with very tight tolerances. But on mine, the barrel extension/receiver has noticeable play on the frame. It rattles a bit when shaken. And the act of pulling the trigger will actually shift the entire barrel slightly to the right, when the linkage presses on the trigger bar.

Is that typical?

If not, are there any recommended methods for tightening it up? I know that smiths sometimes accurize 1911s by compressing the slide rails in a vice to eliminate side play. It looks like that could be done on the Luger (but compressing the frame rails instead.)

DonVoigt · 11-29-2019, 10:30 AM

It is not typical; I know of no reliable way to tighten it. A too tight fit is a more frequent problem.

Since the barrel with front sight , toggle with rear sight are contained in the receiver- they move together.
If you maintain your sight picture and sight alignment, the fit to the lower does not matter.

I would look elsewhere for the accuracy problem- what size group are you expecting?
Look to the crown and muzzle rifling, for damage or uneven wear from poor cleaning practice.

Ron Harding · 11-29-2019, 10:57 AM

As I said, it's a new barrel. Maybe needs breaking-in.

Doubs · 11-29-2019, 11:21 AM

Quote:

Originally Posted by Ron Harding

As I said, it's a new barrel. Maybe needs breaking-in.

Check bore diameter. I've slugged numerous 9mm bores back when I shot a lot of cast bullets and they can be quite large. Typical 9mm bullets are .354 ~ .355" in diameter. I've loaded .357" bullets for some of my 9mm pistols with oversize bores but never for a Luger with an original barrel.

DonVoigt · 11-29-2019, 02:31 PM

Quote:

Originally Posted by Ron Harding

As I said, it's a new barrel. Maybe needs breaking-in.

Sorry,
missed that tidbit.
Then it could be just a bad barrel.

4 Scale · 11-29-2019, 10:26 PM

I have a Luger that had play between the frame and barrel extension/receiver. Like yours, it rattled and depressing the trigger moved the upper to the right. So much so that the grip safety did not work. A weld to add metal to the upper coupled with careful filing/fitting by my gunsmith fixed the issue. However, before and after the fix the pistol was very accurate. As Don explained, even with play between upper and lower the Luger should be accurate.

You might test to see if the safety works.

I suspect the barrel is the issue and would inspect that first. If no issues are detected consider adding metal to remedy the play issue; I suppose at some point too much play might impact accuracy.

rolandtg · 11-29-2019, 11:01 PM

Wonder if they tweaked the receiver when the barrel was changed.

Mac Cat · 11-30-2019, 12:42 PM

Sorry that the barrel length is an issues, but exactly what barrel did you install ?

Eugen · 11-30-2019, 09:18 PM

Detailed photos are always helpful and appreciated.

Ron Harding · 11-30-2019, 09:32 PM

Quote:

Originally Posted by Mac Cat

Sorry that the barrel length is an issues, but exactly what barrel did you install ?

I didn't install the barrel myself. It was installed by the seller. Only legal way to handle it in Canada, since I don't have the license required to possess a "prohibited" pistol. Standard Luger barrels are a wee bit under the minimum length... the law here uses barrel-length as a half-assed way to prohibit concealable "pocket pistols". The Luger is unfortunately caught up in that, despite its overall size.

The new barrel is probably 110mm (just a bit longer.) Don't know the manufacturer. I know Lugerman sells them. So does Dlask Arms in Canada.

gunbugs · 11-30-2019, 10:18 PM

I would argue that a loose frame/receiver fit would very possibly affect accuracy. The shooter is holding the frame, and aligning the sights, which, of course, on a Luger are all on the upper receiver assembly. When you fire it, if the receiver is loose in the frame, it would allow the receiver to flail about, and put the bullet wherever it is pointed when the bullet leaves the barrel. The same can be said for a rifle that does not fit the action tightly in the stock.

G.T. · 12-01-2019, 04:18 PM

I think the loose receiver would have more of an effect on trigger pull then any other reason that might effect accuracy? But, if you're like me, I can't stand something to remain un-fixed, when it is desperately crying out to be fixed!

I would probably squeeze the frame, but only with a thin full length stop plate installed in the frame rail relief slots? And maybe a spacer block for the frame ears as well? I would cut it / them, about .005" under to start.. Try to squeeze it, and then check and see how much more is needed to removed from the plate to allow for adequate distance to be moved, and also to allow for spring back. Just me, on a random Sunday... OK, back to polishing drums.... best to all, til...lat'r.....GT....

4 Scale · 12-02-2019, 12:14 PM

I'm with GT, if a Luger is not functioning correctly the universe is out of balance.

Before bending, welding etc. I suggest careful analysis as to why the parts are loose, In my case both upper and lower had suffered corrosion which had been scrubbed away leaving a loose parts fit. Adding metal was therefore the apparent solution, and worked. If you cannot determine what caused the problem, I suggest contact an experienced Luger-fixer like GT or Lugerdoc.

IMO it is unwise to attempt a fix without first determining root cause.

Ron Harding · 12-05-2019, 12:41 PM

Quote:

Originally Posted by 4 Scale

Before bending, welding etc. I suggest careful analysis as to why the parts are loose

I wish there was a book about the Luger similar to Jerry Kuhnhausen's epic works about the 1911 and M1 Garand.

Most books about the Luger I've seen are not very technical. Mostly stuff of interest to historians and collectors.

4 Scale · 12-05-2019, 05:42 PM

I agree there is a shortage of technical/mechanical data on Luger function. Options to help learn mechanics are referencing a Luger known to function well, high quality Luger animations like this one https://www.youtube.com/watch?v=8DBYV6s1lvo or finding a local resource who knows the pistol. Most gunsmiths do not know Lugers. Careful searching of the forums as well. If you will tell your location perhaps there is a member nearby who could help. Also sending the pistol to experts such at GT or Tom Heller as noted already.

Eugen's suggestion of posting photos is an excellent one. Highest quality you can manage of the contact areas between upper and lower, the barrel, any that you think could help. We have had several people with malfunctioning Lugers post photos over the years and the issue and fix became obvious.

Normally the upper should not rattle on the frame at all, which makes me wonder if something odd has happened to the pistol. I would especially recommend photos here/comparing your pistol to one that is known to work.

11-29-2019, 10:24 AM	#1
Ron Harding New User Join Date: Nov 2019 Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Loose rails and accuracy Hi. New guy here. I have a 1938 S/42 VoPo that I bought for occasional shooting. It was rebarreled with a new Canada-legal barrel (don't even get me started...) Lugers have a reputation for being very accurate pistols. But... I'm having trouble. Shots go all over the place. I get much, much better accuracy from my CZ-75. I've been trying to figure out why. It's all matching-numbers, by the way, not a Franken-Luger. One thing I've been wondering about: Lugers were supposedly made with very tight tolerances. But on mine, the barrel extension/receiver has noticeable play on the frame. It rattles a bit when shaken. And the act of pulling the trigger will actually shift the entire barrel slightly to the right, when the linkage presses on the trigger bar. Is that typical? If not, are there any recommended methods for tightening it up? I know that smiths sometimes accurize 1911s by compressing the slide rails in a vice to eliminate side play. It looks like that could be done on the Luger (but compressing the frame rails instead.)

11-29-2019, 10:30 AM	#2
DonVoigt User Join Date: Apr 2015 Location: near Charlotte NC Posts: 4,681 Thanks: 1,441 Thanked 4,350 Times in 2,040 Posts	It is not typical; I know of no reliable way to tighten it. A too tight fit is a more frequent problem. Since the barrel with front sight , toggle with rear sight are contained in the receiver- they move together. If you maintain your sight picture and sight alignment, the fit to the lower does not matter. I would look elsewhere for the accuracy problem- what size group are you expecting? Look to the crown and muzzle rifling, for damage or uneven wear from poor cleaning practice. __________________ 03man(Don Voigt); Luger student and collector. Looking for DWM side plate: 69 ; Dreyse 1907 pistol K.S. Gendarmerie

11-29-2019, 10:26 PM	#6
4 Scale User Join Date: Nov 2014 Posts: 544 Thanks: 194 Thanked 489 Times in 251 Posts	I have a Luger that had play between the frame and barrel extension/receiver. Like yours, it rattled and depressing the trigger moved the upper to the right. So much so that the grip safety did not work. A weld to add metal to the upper coupled with careful filing/fitting by my gunsmith fixed the issue. However, before and after the fix the pistol was very accurate. As Don explained, even with play between upper and lower the Luger should be accurate. You might test to see if the safety works. I suspect the barrel is the issue and would inspect that first. If no issues are detected consider adding metal to remedy the play issue; I suppose at some point too much play might impact accuracy. Last edited by 4 Scale; 12-02-2019 at 12:06 PM.

11-30-2019, 09:18 PM	#9
Eugen User Join Date: Apr 2016 Location: Newburgh,IN Posts: 790 Thanks: 393 Thanked 631 Times in 334 Posts	Detailed photos are always helpful and appreciated. __________________ “God created war so that Americans would learn geography.” ― Mark Twain

12-01-2019, 04:18 PM	#12
G.T. Lifer Lifetime Forum Patron Join Date: Jun 2002 Location: Chandler Arizona Posts: 3,507 Thanks: 1,318 Thanked 3,653 Times in 1,004 Posts	loose receiver? I think the loose receiver would have more of an effect on trigger pull then any other reason that might effect accuracy? But, if you're like me, I can't stand something to remain un-fixed, when it is desperately crying out to be fixed! I would probably squeeze the frame, but only with a thin full length stop plate installed in the frame rail relief slots? And maybe a spacer block for the frame ears as well? I would cut it / them, about .005" under to start.. Try to squeeze it, and then check and see how much more is needed to removed from the plate to allow for adequate distance to be moved, and also to allow for spring back. Just me, on a random Sunday... OK, back to polishing drums.... best to all, til...lat'r.....GT....

11-29-2019, 10:57 AM	#3
Ron Harding New User Join Date: Nov 2019 Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	As I said, it's a new barrel. Maybe needs breaking-in.

11-29-2019, 11:01 PM	#7
rolandtg User Join Date: Mar 2007 Location: Texas Hill Country Posts: 477 Thanks: 378 Thanked 258 Times in 113 Posts	Wonder if they tweaked the receiver when the barrel was changed.

11-30-2019, 12:42 PM	#8
Mac Cat Lifer Lifetime Forum Patron Join Date: Apr 2015 Location: Austin, Texas Posts: 725 Thanks: 2,089 Thanked 606 Times in 327 Posts	Sorry that the barrel length is an issues, but exactly what barrel did you install ?

11-30-2019, 10:18 PM	#11
gunbugs Lifetime Forum Patron Join Date: Sep 2013 Location: Fairbanks, Alaska. Home of the best moose. Posts: 657 Thanks: 364 Thanked 1,175 Times in 393 Posts	I would argue that a loose frame/receiver fit would very possibly affect accuracy. The shooter is holding the frame, and aligning the sights, which, of course, on a Luger are all on the upper receiver assembly. When you fire it, if the receiver is loose in the frame, it would allow the receiver to flail about, and put the bullet wherever it is pointed when the bullet leaves the barrel. The same can be said for a rifle that does not fit the action tightly in the stock.

12-02-2019, 12:14 PM	#13
4 Scale User Join Date: Nov 2014 Posts: 544 Thanks: 194 Thanked 489 Times in 251 Posts	I'm with GT, if a Luger is not functioning correctly the universe is out of balance. Before bending, welding etc. I suggest careful analysis as to why the parts are loose, In my case both upper and lower had suffered corrosion which had been scrubbed away leaving a loose parts fit. Adding metal was therefore the apparent solution, and worked. If you cannot determine what caused the problem, I suggest contact an experienced Luger-fixer like GT or Lugerdoc. IMO it is unwise to attempt a fix without first determining root cause.

12-05-2019, 05:42 PM	#15
4 Scale User Join Date: Nov 2014 Posts: 544 Thanks: 194 Thanked 489 Times in 251 Posts	I agree there is a shortage of technical/mechanical data on Luger function. Options to help learn mechanics are referencing a Luger known to function well, high quality Luger animations like this one https://www.youtube.com/watch?v=8DBYV6s1lvo or finding a local resource who knows the pistol. Most gunsmiths do not know Lugers. Careful searching of the forums as well. If you will tell your location perhaps there is a member nearby who could help. Also sending the pistol to experts such at GT or Tom Heller as noted already. Eugen's suggestion of posting photos is an excellent one. Highest quality you can manage of the contact areas between upper and lower, the barrel, any that you think could help. We have had several people with malfunctioning Lugers post photos over the years and the issue and fix became obvious. Normally the upper should not rattle on the frame at all, which makes me wonder if something odd has happened to the pistol. I would especially recommend photos here/comparing your pistol to one that is known to work.