Light Primer Strike Issue

[natertot]

I recently picked up a non firing H&K HK4 with one mag. Looked it over and performed the pencil test, which it failed. Everything else seemed to be in order so figured it was firing pin related. Bought it, took it home, and disassembled. I found that the firing pin had broken, but everything else looked good. I ordered a new firing pin and another mag (never can have too many, right?) from Numrich. I got the new FP and installed it. I put a spent casing with marker over the primer into the chamber and test functioned it. The FP hit the spent primer, scratching off marker. I then inserted a cartridge and had a failed to fire. I tap racked, and had another fail to fire. I inspected the primers, and they had been hit, although it was too light to detonate the primer.

Looking at the schematic (found on Numrich website), it appears that the mainspring in the handle causes the force on the hammer to push the firing pin into the primer. After firing, the firing pin spring pushes the firing pin rearward to keep it in place with the hammer and everything ready for the next shot.

If this is true, the light primer strike should be caused be one of two things: 1) weak mainspring or 2) I got an "out of spec" firing pin.

I am not all that experienced with pistol repairs, so I would like to get some advice, input and guidance from those that are and how I should proceed. Thanks for the help.

[hunter63]

I'm gonna say "spring"....and the reason is a recent project with an older H&R 929 that would fire 7 out of 9 positions non firing were light strikes.
Problem was the positions weren't the same ones in the cylinder each time.

Main spring appeared to have been cut form a longer spring so the ends were not finished (flat) but cut mid coil.
Ordered the main spring assembly replace the home made spring....and work fine.

[Rick]

Don't over look the obvious such as bad ammo or lack of lubrication. I've been known to over think a problem or two.

[kyratshooter]

Nate, first thing is disassemble and clean the firing pin channel thoroughly.

Press on the FP at the back and make sure it has proper protrusion. It is an inertia type pin so you will need to push well into the back of the slide. Just make sure that in the fully forward position the tip protrudes a good 20-30 thousandths.

Remove any burrs from the FP and the FP channel.

Check the firing pin spring. Make sure it is not binding on the firing pin or in the FP channel.

Also check the breechface plate where the FP protrudes. This is removable for changing between rimfire and centerfire and may not be seated properly and might be binding against the FP tip or be burred from use.

Check the barrel where it attaches to the frame for "play". This was the HK interchangeable barrel gun and the barrel had to be changed between calibers and there may be some play that has the barrel seating a fraction forward, or there may be play allowing the barrel to move forward, moving the primer away from the FP when it falls. Make sure there is no battering or peening of the barrel seat that is keeping the barrel in a forward position.

Check and see if your buffer pad at the front of the recoil block is in place. They get chewed up rapidly and if the gun was fired without the rubber buffer in place there may be peening at the barrel seat that is causing you a problem.

Contrary to popular belief, not everything the Germans make is perfection.

[natertot]

Check and see if your buffer pad at the front of the recoil block is in place. They get chewed up rapidly and if the gun was fired without the rubber buffer in place there may be peening at the barrel seat that is causing you a problem.

Bingo! The buffer and buffer plate are both missing! Numrich's is out, the search begins!!!!!!

Thanks kyrat!

[kyratshooter]

Also check the screw that holds the breech plate to the slide. If that screw is too long and protrudes, or has a burr that protrudes it can keep the breech away from the cartridge face. The head of that screw is aligned with the top of the barrel hood and ot not being completely seated in its recess could cause a problem.

You also need to make sure your pistol has the proper recoil spring for the caliber. Most of these guns came with a CF and a .22 barrel, and some came as 4 barrel sets. Each barrel had a spring calibrated for the cartridge it shot.

If you ever get this thing shooting I suggest super gluing everything solid and never touching it again except to shoot WD40 into it and run a patch down the bore!

You are probably not going to find a buffer for that pistol. Might as well resign yourself to making one. I would recommend using neoprene from a piece of water well pipe. Or you could scarf a 1911 slide buffer insert and cut it to fit. They are tough as nails and made for the same purpose as the HK4 buffer. I have a couple of those extra and will bring one next time I see you.

[natertot]

Also check the screw that holds the breech plate to the slide. If that screw is too long and protrudes, or has a burr that protrudes it can keep the breech away from the cartridge face. The head of that screw is aligned with the top of the barrel hood and ot not being completely seated in its recess could cause a problem.

You also need to make sure your pistol has the proper recoil spring for the caliber. Most of these guns came with a CF and a .22 barrel, and some came as 4 barrel sets. Each barrel had a spring calibrated for the cartridge it shot.

If you ever get this thing shooting I suggest super gluing everything solid and never touching it again except to shoot WD40 into it and run a patch down the bore!

You are probably not going to find a buffer for that pistol. Might as well resign yourself to making one. I would recommend using neoprene from a piece of water well pipe. Or you could scarf a 1911 slide buffer insert and cut it to fit. They are tough as nails and made for the same purpose as the HK4 buffer. I have a couple of those extra and will bring one next time I see you.

Thanks, Kyrat.

All screws are good to go. Springs seem in good order, including the recoil spring. I found a guy on the HKPro forums that make these buffers and sells them in sets of 2 for $30. I am ordering them and installing one. If this fixes it, the gun will be for sell. I bought this as a project gun and for what I have into everything, it would be beneficial to sell it in working order. As hard and expensive parts are for this thing, I do not want to keep it. I like to keep guns that can be repaired easily.

[kyratshooter]

That particular gun was the HK entry into the pistol market, 1967.

They had been providing the G3 to the German army and much of the rest of the world, but had never produced a pistol.

This one might have been a bit much for their first effort.

The 2 gun and 4 gun boxed sets are serious collector items.

I am sure you will be able to sell it and make some profit. People go cross eyed over anything HK related.

[natertot]

People go cross eyed over anything HK related.

Exactly why I didn't mind buying a broken one for next to nothing. I figured worse case scenario, I could part the thing out and still quadruple my investment. But, now that this thing is sooo close to working, I'd really like to get it there and sell it off. I'll have to wait for the buffer to come in and go from there. It is kind of an interesting pistol and concept. Almost like the H&R Handi Rifle or Rossi SS interchangeable barrel stuff, except in the pistol realm. Too bad they couldn't get the thing on track and discontinued it. Oh well......

[DaddyOh]

If you insert the firing pin without the spring how far does it penetrate the bolt face? If you get a good fit here then it is a spring. Possibly the main spring, or the firing pin spring may be bad and does not hold the pin ready for impact.

[natertot]

If you insert the firing pin without the spring how far does it penetrate the bolt face? If you get a good fit here then it is a spring. Possibly the main spring, or the firing pin spring may be bad and does not hold the pin ready for impact.

If you knew how the firing mechanisms worked on this pistol (or read post #1), you would know that the firing pin spring does not have anything to with the actual firing. The firing pin spring applies rearward pressure on the firing pin to keep it held against the hammer. Without the spring, it wouldn't even penetrate the bolt face because it would not be inserted in a way that the hammer could do it's job.

Between this post and the post on Rick's S&W .38 revolver bluing thread, I am starting to wonder if you are a troll trying to be a gun saboteur. I hope you input on firearms doesn't hurt or kill someone, but then again, that might be your mission.

[Rick]

He's not. He's just focused on end of the world stuff and clearly ticked at me and Crash. The fact you posted that you found the problem might have been a clue though.

[hunter63]

He's not. He's just focused on end of the world stuff and clearly ticked at me and Crash. The fact you posted that you found the problem might have been a clue though.

That's kinda my impression.....there seemed to be an echo, echo, echo,

[crashdive123]

Why is it that those who plan for the end of the world seem so disappointed when either you don't agree with them or they are shown to be wrong.


Sent from my iPhone using Tapatalk

[crashdive123]

And I should add.....

or if the world doesn't end?

[kyratshooter]

That reminds me, I need to get my flu shot!

Got guns, got ammo, got food and water,

But what will get us all is probably going to be a microscopic bug.

What size shot and what is the best gauge to use use for germs?

[hunter63]

Honeeeeeey, gonna be needin' a bug gun.....Kyrat saiiiiiid.

.17 HMR do it for bugs..........

[Rick]

22-25 gauge is recommended. Honest.

http://www.immunize.org/catg.d/p3084.pdf

[finallyME]

Man, I have been having somewhat similar problems with my nylon 66 .22 LR. It fires maybe 10 out of the 13, and won't fire the other 3. At first I thought bad ammo, but I can usually take that one that didn't fire, and put it in another rifle or handgun and get it to work. Now I am thinking spring. Anyways, sorry about the derail.

[DaddyOh]

[QUOTE=natertot;443614]If you knew how the firing mechanisms worked on this pistol (or read post #1), you would know that the firing pin spring does not have anything to with the actual firing. The firing pin spring applies rearward pressure on the firing pin to keep it held against the hammer. Without the spring, it wouldn't even penetrate the bolt face because it would not be inserted in a way that the hammer could do it's job.


Yes. If you remove the firingpin spring and insert it into the slide, you will be able to see if the pin will protrude thru the hole far enough for a good contact with the primer. This is a standard step with fp problems, and shoulda been the first thing tested on a weapon that didnt work when you bought it.

Rick and his alts...