Breech Block Failure 1916/1920 Erfurt

[Allen Brett]

UPDATE:

I ordered and old "new stock" breech bolt that arrived in perfect condition. I swapped the breech out and put the firing pin and extractor from the original into the new block. The pistol will now cycle a new round with no problems (this was done manually and I did not fire the pistol). The next process was to check the headspace which is the current problem. I called all 3 gunsmiths where I live and they only do headspace work on bolt action rifles.

One of the three told me to pull the firing pin and extractor then use masking tape one layer at a time to see if the round would feed while slowly letting the toggle down. In short I ended up having to add 5 layers before the breech will not close when letting off the toggle slowly so the round is not being slammed in place. I used my calipers and the thickness of the 5 layers is 0.017. I found the following on a google search which took me to "LUGERFORUMS" and it stated the following "minimum headspace measurement from a SAAMI chart is 0.754" and the maximum headspace is 0.776", or 0.022" difference."

My question is using the factory round and having to add 0.017 before the shell would stop means I should be at 0.771 or slightly less which would put me under 0.776? If this is correct I should be within specifications to shoot factory loads?

Thanks,

[gunbugs]

The only way to actually check headspace in with the correct gauges. A cartridge is an unknown dimension, compared to a gauge. Tape is not an accurate way to gauge headspace. Bad idea. I would not take my firearm to said "gunsmith" for any work.

[Allen Brett]

No one around here want's to touch a 105 year old Luger. As you can see I live in central Wyoming and we have a lot of "custom rifle builders" along with a few older guys that work on revolvers and old lever action Winchesters. I have yet to see an all around smith
which of course concerns me.

[G.T.]

A normal commercial 9MM brass case runs approx. .010" under the "GO" or minimum, so you .017"+ addition puts you right about in the middle of the range?... Make sure you check your first shot, and maybe a few more for primer damage/... best, til....lat'r...GT

[G.T.]

BTW, Allen, send the top half complete to me, I'll check it for you, no problem, no charge.... best, GT

[Kiwi]

gunbugs, you may be a little harsh on the gunsmith. He probably has guages but will not loan them out. He just gave a suggestion on how Allen can make a rough check himself.
Much like the suggestion on the to use masking tape for excessive toggle slap
http://forum.lugerforum.com/showthre...le+slap&page=2

Unscientific, not an accurate measure, but gives one an idea whether there is a problem or not
In this case Allen's gun is on the edge and worth paying to have the headspace measured

[Allen Brett]

Thank you for all of the comments and especially to G.T. for his generous offer. I decided to try one last procedure and I think this the best so far short of an actual gauge. I took a piece of spent brass, removed the primer and put it through the sizer in my loading die then measured the case length at 0.747 and chambered it no issue. I then added a trimmed tape disc up until the bolt would not close with a light steady pressure. I measured the casing with the tape disk on it that would not allow it to go into battery with the noted light pressure and the length is 0.768. I also measured the factory loaded case I used prior and as G.T. stated it was exactly 0.744 which puts it .010 under the standard of 0.754. So I would think at 0.768 with the case not going into battery I should be within the "SAAMI chart is 0.754" and the maximum headspace is 0.776", or 0.022" difference."

[Mark1]

Hi Allen,
You are on the right track. If your measurements are accurate, a headspace of 0.768" is well within the SAAMI range, although a little over the CIP standard. Regardless, the pistol should be safe to test fire and then examine the fired cases for any problem. If there is an issue, I'd recommend you send the gun to GT for a close inspection.
Use of tape discs on a sized case head is an acceptable method of checking headspace, if the accuracy limitations are understood. I regularly use this method for obsolete calibres where any standard gauges are unavailable.
Mark

[Heinz]

Allen, a free check by G.T. could save you lots of problems later. I believe you can send it priority mail

[ithacaartist]

Originally Posted by Heinz

Allen, a free check by G.T. could save you lots of problems later. I believe you can send it priority mail

Unless I'm mistaken, only if you're an FFL holder. USPS regs make us plebeians use UPS or FedEx overnight at around $80.

[Doubs]

Originally Posted by ithacaartist

Unless I'm mistaken, only if you're an FFL holder. USPS regs make us plebeians use UPS or FedEx overnight at around $80.

The frame is the gun. The upper assembly - barrel, receiver & toggle system - can be legally mailed without an FFL.

[gunbugs]

Actual gauges are not that expensive, compared to any Luger. They can be had at reasonable prices, here,https://www.brownells.com/gunsmith-t...9%2bmm%2bLuger

[Allen Brett]

I think "gunbugs" is right on this. I paid $1,000 for the pistol along with $65.00 for the new breech block and planned on shooting it. By the time I pay to mail it both ways insurance, etc. I could order a "no go" gauge which is all I think I need at this point to confirm I don't have too much headspace.

Thanks again for all of the help on this project!

[schutzen-jager]

Originally Posted by Doubs

The frame is the gun. The upper assembly - barrel, receiver & toggle system - can be legally mailed without an FFL.

not true in all cases check ATF regulations - in some cases the upper receiver is the controlled part ! - IE Ruger standard .22 auto + many others - from old atf info booklet -

[DonVoigt]

Barreled receiver can be mailed in one box.
The toggle in a separate box.

I think the reference page shows/states that later on.

But I agree, just buy a no go gage!

[schutzen-jager]

Originally Posted by DonVoigt

Barreled receiver can be mailed in one box.
The toggle in a separate box.

I think the reference page shows/states that later on.

But I agree, just buy a no go gage!

correct - it is stated in attachment to my post that barrel + receiver does does not constitute a firearm , but barrel , receiver , + toggle does - but they can be mailed separately + be legal -

[Heinz]

Mail it to GT.. Get a gauge if you want it going forward, but a full professional check is well worth the USPS postage, two small flat rate priority mail boxes.

[gunbugs]

So, the way I see it, past "how do we fix it"...Begs the question,"what is the cause of the failure". Obviously, the extractor tried to beat its way through the slots in the breech block. Why?.... I can see a ruptured cartridge, or some other ammo failure trying to blow the extractor out of the top of the block, but our O.P. says the ammo functioned normally, and the brass looks good. I can't see the parts being so badly fitted by the boys at Erfurt that they sent out a pistol doomed to failure. It seems to me that the little "ears" on the extractor were being forced up into contact with the cuts in the block, and some type of overtravel situation occurred. But, it again begs the question, What is the cause? Too long of a hook on the extractor? Abnormally large diameter rims on the cartridge? What was forcing the extractor up so hard? A weak extractor spring, allowing the extractor to flail upwards without resistance? Without knowing the cause, we may not be fixing anything.

[Green57]

gunbugs,

I think you might be on to something with this statment "Abnormally large diameter rims on the cartridge?"

I have a S&W model 1917 that shoots .45 ACP utlizing moon clips. Normally I shot WWB or RGB ammo out of it. Went shooting one day and Wally world was out of the normal ammo so I bought some Blazer brass.

It was noticablly harder to snap this ammo into the moon clips, to the point that I decided it was not worth the effort. The only reason I could think of that would make the Blaser harder to load into the clips was if the extractor groove diameter was at the upper limits. It did shot fine through my Colt WWI reissue though.

I wonder if the Blazer 9mm cases are manufactured towards the upper limits like their .45 is? Might be worth breaking out the calipers to measure the groove and rim diameters on the case to find out if this could have been a contributing factor to the BB failure.

G57

[G.T.]

When a primer is pierced, the rapid occurrence of breechblock damage is from one thing only, and that is escaping high pressure gas going back, and going up! One has to remember, the breech is locked during the first few milliseconds after firing. The only mechanical movement is inertially back, with the complete top end involved, the damage is most likely done before the receiver ever even starts to move... I have seen this progression to failure with my own eyes, and three shots is about the max you get... correct the headspace issue, and the problem goes away! I am so paranoid about this that I always make sure the toggle train closes tight on the "GO" gauge, (yes, you need both gauges!) when installing new or old original barrels. Excessive head spacing can be a result, or combination of the following. Breechblock at one end or the other in tolerance, barrel chambered too deep, wear on any or all of the three main toggle train pins. It adds up fast! Good luck to all when shooting a loose gun! ... best to all, til.....lat'r....GT...