Breech Block Failure 1916/1920 Erfurt

[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...

[gunbugs]

I understand the operation on the locking/unlocking system on the Luger, and other firearms. However, the O.P. states that no pierced primers were evident in this occurrence. So, that being said, why would the extractor beat its way through the top of the block? Even with a couple thousandths excessive headspace, the cartridge should obturate, and seal the chamber from gas leakage. I deal with firearms that have excessive headspace on a fairly common basis, and the typical symptom is stretched brass, not gas leakage. Even a pierced primer should not leak enough gas to make an extractor try to leave the gun. Again, the O.P. states no pierced primer here.

[DonVoigt]

Gunbugs makes a great point about the OP; unfortunately many do not read or forget the statement of the problem, nor do they read all the subsequent comments.

I still say that for a 100 year old metal part, with unknown history of how many times or with what ammunition it was fired, to fail.

The thin areas that broke out, have "hidden" sharp corners on the underside, a favorite place for fatigue cracks to begin.

With no pierced primers and what is a fairly common failure mode- the cause for the failure will likely never be determined.

[Allen Brett]

I have ordered the "no go gauge" and will start there. The barrel was never changed out as noted all matching serial numbers up to the point of the breech block failure other than possibly the firing pin which I did not check for matching. I did note the firing pin is fluted which indicates the pin itself may have been changed at some point. The theory on the rim size is intriguing as I have an old "Star" 9mm that jams on the Blazer Brass and works flawless on Remington. I have 2 uneducated guesses on what may have caused the problem if that is even a possibility. I came across a factory cartridge one time where the bullet was set probably 1/3 deeper than the rest however, that should not have affected headspace? Needless to say I did not fire the round out of the Glock at the time and I disposed of the round. Is it possible as "Karl" suggested that for whatever reason the mechanism did not go into full battery? If this is the case could the pistol still fire and that be the cause of the problem? There is really not anything else I can think of as the rest of the parts are in good shape. I shoot a WWI DWM all matching that I have however, only on occasion and all I have ever used is Remington ammo with no problems.

[G.T.]

Hi gunbugs, a quick and easy indicator, for Allen, of what might, or might not have happened would be a quick look at the rear of the breechblock for firing pin and retainer damage at the rear of the block? With the ejector retainer broken out, it is almost certain that the retainer area at the rear of the breechblock is damaged severely as well... If no damage there, then the ejector area failed mechanically with something causing it to exceed it's yield strength??? Best, til....lat'r.....GT...

[Allen Brett]

G.T. here are some better photos of the damaged breech block.

Thanks again for all of the follow up from everyone.

[spangy]

Well you sure blew the lips off that one Allen.

[Allen Brett]

Yep..

[Allen Brett]

Thank you G.T. your help has been much appreciated. I will try the gauge first then a test shot and check the case/primer. If no go it will be on the way to you. I have a couple of P-38's and old Hi-Power and another Luger I have never checked so the $30.00 gauge will get some other use.

[G.T.]

Hi Allen, at least with the forum help, you have a lot more info than when you started! .... As for the gauges, once you have the "NO GO" you can use it as a base guide dimensionally and put scotch tape on the back of a regular empty and make your own "GO" gauge! I've done it many times, and even made incremental sets to see just where I was at when re-barreling?.. I pay a'lot of attention to where the toggle knob is in relation to the receiver rail when using gauges, both "GO" & "NO GO" on closing. You'll get a feel for the exactly right head spacing, more importantly, you'll have a baseline if ever a problem should arise... If possible, I like the action to close tightly on the "GO" .... seems to work out fine in the overall picture.... best to you Allen, til....lat'r.....GT...

[Allen Brett]

Thank you everyone for all of the guidance and comments! I will post back how it all works out in the next few weeks. The forum members here are so helpful and knowledgeable. I wouldn't have stood much of a chance without them and I have learned so much about the Luger pistol and the parts that make it work.

[mrerick]

Is that pitting corrosion around the axle pin engagement hole? Also some galling?

That would indicate moisture got inside the breech block and toggle train. Corrosion could generally weaken the entire block, as well as retard unlock and cycling by resisting rotation around the axle pin.

While the firing pin hole looks considerably enlarged (more possible evidence of corrosion inside the block), if there were no pierced primers the only path possible for high pressure exhaust gases is around the case, past the oblation ring and back into the face of the breech block before it unlocks and extracts.

That would imply that the cartridge might not be against the chamber case stop ring. Is the interior of the chamber pitted? Is there forward / rearward play in the toggle train?

Would resistance caused by friction and pitting at the breech block axle delay extraction enough to allow the blowback around the case into the breech block?

The "go" and "nogo" headspace gauges are useful when cutting a barrel's chamber, but you need a "field" gauge to verify that you don't have excessive headspace.

[Allen Brett]

Update:

I received the "Clymer No Go" gauge, pulled the firing pin and extractor from the pistol then inserted the gauge and let off slowly on the toggle until it stopped. I then checked to see if the pistol was in battery and it was not. I applied some pressure and it would not budge. There is no question that I do not have too much headspace. I then used a sized, de-primed factory casing and added layers of tape until it would just close with no added pressure required. I measured the case at 0.764 and as noted the Clymer gauge would not lock down or go into battery even with some moderate pressure no movement. So based on the Sammi headspace being 0.754 with up to 0.22 allowance for a max of 0.776 I should be good to go on a test fire?

The more I looked at the breech and where it failed up close there appears to be almost small bubbles in the metal or more what one would see in "pot metal" or cast iron. I think as many have said the failure may have been just due to age and wear. The only issue I could see now is if for some reason the firing pin pushes through too far on a primer? The rest of the parts are all in excellent shape and the replaced "old stock" breech block looks to be new other than the number does not match.

[Allen Brett]

...

[Allen Brett]

I sized a piece of brass, inserted a primer and test fired the empty casing to make sure the primer strike looked good. I inspected the primer after firing and it was right on the money, not too deep and not too light. I think we are ready for a test fire!

[Heinz]

we are waiting Allen :-)

[Allen Brett]

Hoping to try it out this weekend. Two weeks plus of below zero weather, snow and wind gusts of up to 80 mph before and after.

[Allen Brett]

I just returned from the range after completing all of the prior noted. The pistol functioned flawless through 2 magazines with no issues. Thanks again to everyone for all of your help!

[Fla.Mallard]

I have that exact model and this situation 'scared' me into retiring it as a shooter.

Thank you for posting.