Problem with bolt hold open on 1918 DMW
 

I have a 1918 DMW which is in excellent condition, except that someone reblued it. They did a fine blue job, but there goes any collector's value. When I bought it, I replaced all the springs, except mainspring - just could not get the Wolff spring into the pistol.

Of late, I have had trouble with the bolt not locking to the rear on an empty magazine. The bolt hold open goes up and down just fine with the pistol field stripped and an empty magazine in the pistol. The hold open clearly functions.

But when I put the pistol back together, it won't work. New hold open spring and a little light dressing of the hold open arm didn't help. The hold open recess in the frame is clean and looks to be OK. I did notice that the cut out on the bottom of the bolt that presumably catches the hold open is a little nicked. But it was that way when I got the pistol, so I don't know if that is the problem.

Any ideas?

Thanks,

Jim

Was it ever working properly?
Did problem occurred only after you replaced all of the springs including magazine spring?
Is this happening only when live firing?

It did work fine originally. I failed to mention that the hold open issues occurs with both WWII era magazine that comes with it and 2 new Mec-Gar I bought.

One of the only problems the pistol had when I bought is was a broken hold open spring. I replaced that with a new SARCO spring.

Hold open spring is still "rubbing" somewhere, I've experienced the same problem in replacing the spring. Look harder!
HO spring may just be too strong too.

Thanks. I'll continue polishing the spring area.

If it is too strong you will have to change it again, or thin it.

Do you have another HO to switch in to test?

Just curious. What kind of ammo are you using? Reloads or factory?

I wondered if the SARCO spring may be too "heavy" since it's new manufacture. I'll try thinning it a bit when I polish the HO.

I was shooting all kinds of ammo in it - both reloads of various bullet weight and some Russian factory 115gr FMJ. I chronographed the reloads in my CZ 85 to make sure I had velocities comparable with factory loads of the same bullet weight. I don't "hot-load" although I have read in several sources that Lugers like stiff loads.

Ignore those sources.
Ron

Before polishing the HO spring too much, try removing the spring to see if it locks open. If it doesn't it's not related to the spring.

what is the statis so far??

Have you tried different mags? I have seen this problem in a few guns, and it was related to the insertion depth of the mag. If it doesn't sit deep enough, it won't push up the hold open far enough to catch the bolt. I have fixed a few by simply swapping mags and hold opens (could possibly be related to the mag release as well), but you may not want to do that if the gun is matching.

You could take the mag out, then work the latch with a screwdriver to see if it catches the bolt. It will probably be a three hand operation, but it should be possible. If it does catch, I'd say the mag is just not pushing it far enough.

In replacing the HO spring purchased from Sarco, I found the spring to be WAY too thick...I had to reduce the thickness by polishing it down a lot with a Dremel and a rubberized polish wheel...I do know that it does not need to be that strong...Just enough to drop the HO down when you pull up on the toggle...The stronger it is the more the mag spring has to push it up anyway...
Hope this helps...

The mag spring is (or at least should be) way stronger than the latch spring, so it should push up easily as long as the mag follower can hit it and move it far enough. You may be on the right track, but I really think your problem is in the movement of the parts.

It is not all in the strength of the spring; if the thickness and shape and length, combine to bind when the receiver is in place, the HO cannot move up sufficiently.

It was the Sarco spring, it was too heavy. A little polishing of the spring and the HO works fine now.

Thanks to everyone for the suggestions.

I thought as much...I had same problem...Glad it is fixed...

The spring was "too heavy" so "a little polishing" fixed it? I need help in understanding what you did to the spring and what was corrected. Could you elaborate? By heavy do you mean too large or strong? How did you polish it, how much and with what? :confused:

To lighten a spring by polishing can be accomplished with a Dremel tool. You just need to:

Never let the spring overheat, have a water container handy, you grind it a bit and when you feel it heating you stop and dip into the water to cool. This will prevent the spring to loose it's temper.

Also, you grind it/polish it length wise.

That's the basics. Hope some expert comes along and explains it better.

I didn't use a dremel; my oldest some chewed up all the abrasive bits working on his 1966 Mustang.

So, on the initial premise that the sides of the HO may be binding, I used an Arkansas stone to polish the edges of the HO. This would also hit the spring where it is inserted into the HO. That didn't work.

Next, I took a pair of end-cutters and lopped off about 1/32" from the skinny end of the spring. That didn't work.

Finally, I used the Arkansas stone to lightly remove material from all four sides of the spring end that sticks beyond the HO. And I mean lightly. I kept stoning and testing until the HO worked.

In fact, I removed very little metal. You couldn't tell it had been touched except that the bluing on the spring end rubbed off.

I think what finally did the trick is that I got the thickness of the spring down just enough to have it's pressure be compatible with the pressure the magazine follower and its button put on the HO. They are in balance now, I believe. Time will tell.