No second shot
No second shot
I took the original buffer spring that came with my parts kit, and trimmed it per suggestions I found in the forum. The bolt now seems to go into battery. My problem now, is that I can't get a second shot off. When I manually charge the first round, the gun fires. The second round is merely a click. I can manually cycle the gun and it does extract okay, it fires , and then the same thing happens. The unfired round has a slight dimple on it, so I'm assuming the firing pin is making contact, but not with enough force to detonate the primer. Don't know where to start. Initially I thought the firing pin might be binding, but why would the first round detonate and not the second? Another note, I have a little side to side wobble in my gripstick, would that be contributing to the problem. But again, wouldn't that cause problems on the first shot as well? Itching to correct this, I just don't know where to start.
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JBaum
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Re: No second shot
You should never trim the buffer spring. You probably mean the recoil spring?
If the grip is a bit sideways and the hammer is hitting on the bolt extension before it hits the firing pin, it might not have enough force to hit the primer hard enough to ignite it. See if you have marks on the bolt extension where the hammer has been hitting. If the hammer hits the firing pin at an angle, it can cause the firing pin to have friction going forward and not have enough force left to ignite the primer. Is the firing pin lubricated?
It's also possible the bolt isn't fully locked to the barrel extension for your second shot, and the firing pin isn't protruding far enough to hit the primer because there is a little bit of space between the rear of the cartridge and the bolt face, and if so, you'll get a light primer strike. Is the extractor properly in the cartridge extractor groove?
"The bolt now seems to go into battery." It either does or doesn't. Check it and make sure.
"The second round is merely a click." What does that mean? You hear the cartridge? Firing pin? Hammer? Does the hammer hit the firing pin? Is the hammer cocked?
There aren't many movements inside the gun when it functions properly. Check each one in order and see which one isn't right.
If the grip is a bit sideways and the hammer is hitting on the bolt extension before it hits the firing pin, it might not have enough force to hit the primer hard enough to ignite it. See if you have marks on the bolt extension where the hammer has been hitting. If the hammer hits the firing pin at an angle, it can cause the firing pin to have friction going forward and not have enough force left to ignite the primer. Is the firing pin lubricated?
It's also possible the bolt isn't fully locked to the barrel extension for your second shot, and the firing pin isn't protruding far enough to hit the primer because there is a little bit of space between the rear of the cartridge and the bolt face, and if so, you'll get a light primer strike. Is the extractor properly in the cartridge extractor groove?
"The bolt now seems to go into battery." It either does or doesn't. Check it and make sure.
"The second round is merely a click." What does that mean? You hear the cartridge? Firing pin? Hammer? Does the hammer hit the firing pin? Is the hammer cocked?
There aren't many movements inside the gun when it functions properly. Check each one in order and see which one isn't right.
Re: No second shot
My mistake, recoil spring. The click is the hammer, it sounds like it's functioning properly when I pull the trigger, just doesn't fire. The problem I had with the SA recoil spring I had purchased was that the bolt would not go all the way forward, the modified recoil spring took care of that issue, as well as my failure to feed issue I had mentioned in an earlier post. I'll try your suggestions. What I'm still confused about, is why does the first shot go off when I first charge the gun, and not from the action of the gun itself? Thanks jbaum.
Re: No second shot
John brought up many good points. If I may add a few...
Friction/binding is the worst enemy of a SA MG42 platform, be it rails, tight links, hammer contact with the bolt extention etc.
First is the hammer could be slightly scraping on the bolt extension scrubbing off it's impact on the F/P. I would cover the hammer with dye-chem and work it to see if its rubbing off. If the G/S is moving, this could be whats happening. I cut a window on the top of my bolt extension so that I can see the hammer/FP relationship when fitting.
The hammer could be clearing fine when hand cycling, but under pressure if the G/S is loose enough it could be tipping to one side just enough that the edge of the hammer could be dragging on the bolt extension...it doesn't take much to scrub off energy.
Sometimes too a heavy hammer spring can remedy this as well if you are using the AR type G/S, but eliminating any contact or binding is the key. The H/D spring IMO is best suited for hard primers.
Another thing is the bolt may not be going back fully into battery. A couple of things can cause this. The first two possibilities I would look into is if the gun is getting enough pressure to fully cycle. Going down one size with a booster nozzle could help this (adding pressure), this is how the gas pressure is set on this platform, be it a tight/loose gun, ammo differences, temps etc..
I keep several sizes in my tuning kit. The cones are getting harder to find in the smaller sizes like 10mm...most Yugo kits I've seen come with 11-13mm....which is usually fine for a broke-in 8mm FA, but a new rebuilt S/A can require more gas pressure.
A tight new gun sometimes works best with a 10mm nozzle (normally used in .308, but sometimes is needed in 8mm depending on a number of factors). If you don't have one Numrich sells a couple sizes bigger (I think they had 11 and 13mm left last I knew) and you can weld around the outside hole, then drill it out to 10mm. You probably have an 11 or 12mm in your Yugo kit. Once your gun breaks in move back up in size. Too small, too much pressure beats the guns unnecessarily and can cause other problems.
Another thing is the recoil spring could be cut too short, making it not strong enough now to push the bolt fully back into battery after stripping a round. If the rollers are not fully out you can get light primer strikes, which keeps the gun from firing OOB.
That said, I like using the new MG3 recoil springs RTG sells when kit building. It is apparent when you compare a new spring to an old kit spring how much set they have taken over 50 years or so if you compare them.
What I do is cut it on the long side, then with the cover off (hand cycling with no ammo of course), pull it back and watch to see if it bottoms out. You do not want the bolt carrier to bottom out on the recoil spring (thats what the buffer spring is for), you want as much spring as possible though without it bottoming on itself. Trim just a bit off at a time till you can see that when fully pulled back that the bolt is impacting the buffer...this is as much recoil spring length that you can run in your S/A.
FP protrusion can be another issue as well.
Friction/binding is the worst enemy of a SA MG42 platform, be it rails, tight links, hammer contact with the bolt extention etc.
First is the hammer could be slightly scraping on the bolt extension scrubbing off it's impact on the F/P. I would cover the hammer with dye-chem and work it to see if its rubbing off. If the G/S is moving, this could be whats happening. I cut a window on the top of my bolt extension so that I can see the hammer/FP relationship when fitting.
The hammer could be clearing fine when hand cycling, but under pressure if the G/S is loose enough it could be tipping to one side just enough that the edge of the hammer could be dragging on the bolt extension...it doesn't take much to scrub off energy.
Sometimes too a heavy hammer spring can remedy this as well if you are using the AR type G/S, but eliminating any contact or binding is the key. The H/D spring IMO is best suited for hard primers.
Another thing is the bolt may not be going back fully into battery. A couple of things can cause this. The first two possibilities I would look into is if the gun is getting enough pressure to fully cycle. Going down one size with a booster nozzle could help this (adding pressure), this is how the gas pressure is set on this platform, be it a tight/loose gun, ammo differences, temps etc..
I keep several sizes in my tuning kit. The cones are getting harder to find in the smaller sizes like 10mm...most Yugo kits I've seen come with 11-13mm....which is usually fine for a broke-in 8mm FA, but a new rebuilt S/A can require more gas pressure.
A tight new gun sometimes works best with a 10mm nozzle (normally used in .308, but sometimes is needed in 8mm depending on a number of factors). If you don't have one Numrich sells a couple sizes bigger (I think they had 11 and 13mm left last I knew) and you can weld around the outside hole, then drill it out to 10mm. You probably have an 11 or 12mm in your Yugo kit. Once your gun breaks in move back up in size. Too small, too much pressure beats the guns unnecessarily and can cause other problems.
Another thing is the recoil spring could be cut too short, making it not strong enough now to push the bolt fully back into battery after stripping a round. If the rollers are not fully out you can get light primer strikes, which keeps the gun from firing OOB.
That said, I like using the new MG3 recoil springs RTG sells when kit building. It is apparent when you compare a new spring to an old kit spring how much set they have taken over 50 years or so if you compare them.
What I do is cut it on the long side, then with the cover off (hand cycling with no ammo of course), pull it back and watch to see if it bottoms out. You do not want the bolt carrier to bottom out on the recoil spring (thats what the buffer spring is for), you want as much spring as possible though without it bottoming on itself. Trim just a bit off at a time till you can see that when fully pulled back that the bolt is impacting the buffer...this is as much recoil spring length that you can run in your S/A.
FP protrusion can be another issue as well.
Re: No second shot
Thanks Der Adler. I'm going to try and sit down tomorrow night and look at the areas you and John suggested. I think I have a new recoil spring laying around, so that's a plus. As far as the booster cone, I've got mine set up for 308, consequently I ordered the nozzle/ cone a while back, it's a one piece deal. Any suggestions should I have to replace it. Again, I really appreciate the input you both have given me.
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JBaum
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Re: No second shot
The advantage to the old style booster is that it's adjustable by using different nozzles. You might end up needing to use it.
Re: No second shot
I broke the gun down the other night, and found some possible trouble spots. I've noticed the firing pin tends to bind somewhat on the hole through the feed stud shaft. I had some problems inserting the BRP feed stud in the bolt and think I may have taken too much material off the stud to get it into the bolt, i.e stud was too big around. I believe the stud is working loose when I fire the gun, pinching the firing pin. I've ordered another stud assembly and plan on replacing the undersized one. My question is whether the stud needs to penetrate all the way through the bolt. Could I simply take the feed stud I initially removed from the bolt, cut off the shaft, and weld the remainder to the bolt? I'm talking about the feed stud that originally came with the bolt, not the BRP one. The other thing I noticed was that the end of the firing pin, where the hammer strikes, is peened on the bottom, like the hammer is not getting a full strike on the pin. I plan on drilling a hole in the top of the bolt extension, as per Der Adler's suggestion, to see what's going on there. I also plan on trying to eliminate the wobble in the grip stick. I may have made the slot where the gripstick locks in, a tad too wide. So, that's my progress so far. Again, I appreciate all the advice you guys have given me.
Re: No second shot
One of the functions of the stud is to capture the ejector button (the piston-like part at the rear of the bolt carrier), so the shaft is needed....(amusing you meant removing the lower shaft portion).
What I do when I install the BRP type roller pin (which uses a nice roller bearing in the head) is I ream out the hole *slightly* (because it is way too tight IMO), then I use a vise as a press to press the pin into place, along with some oil to help the process. You want it to be tight so that is does move as if it twists or get out of alignment with the FP is will cause binding on the rear of the FP.
What you could do is if its getting out of alignment (turning) is counter sink the bottom hole slightly (don't break all the way through the B/C body), them weld over it and smooth it with a dremel. There is no pressures on it other than holding the ejector button and rear of the semi F/P so this should be fine so long as it is secure.
I don't see why you could not use an original stud so long as it was drilled in the proper location, but thats the thing, when you drill it the hole has to be big enough for the FP, if you don't get the hole located correctly it will cause more F/P binding. BTW if the F/P is biding slightly even after the alignment issues are worked out, you could chuck it into a drill press and take a very slight amount off the rear where it passes through with a file, then smooth it with some emery cloth...basically a home builders way of turning it down.
On the F/P peening, it could be the hammer is hitting the F/P before its full stroke, which may be why the bottom edge of the F/P is peening. Like I had mentioned the best way to tell is with a window on the top of the B/C extension, that and some dye-chem on the hammer face may help. If thats the case you may need to make some adjustments...which there are a number of ways to deal with that depending on exactly whats happening (we can get into that once confirmed).
BTW I have noticed that many of the semi auto firing pins are somewhat soft and will peen from hammer strikes. I remedy that by home heat treating (hardening) the rear of them.
Here is a pic of a couple of my B/C's, the top is a Wiselite type, that had a window pre-cut, the bottom is a BRP "kit" type which I cut my own window in.
What I do when I install the BRP type roller pin (which uses a nice roller bearing in the head) is I ream out the hole *slightly* (because it is way too tight IMO), then I use a vise as a press to press the pin into place, along with some oil to help the process. You want it to be tight so that is does move as if it twists or get out of alignment with the FP is will cause binding on the rear of the FP.
What you could do is if its getting out of alignment (turning) is counter sink the bottom hole slightly (don't break all the way through the B/C body), them weld over it and smooth it with a dremel. There is no pressures on it other than holding the ejector button and rear of the semi F/P so this should be fine so long as it is secure.
I don't see why you could not use an original stud so long as it was drilled in the proper location, but thats the thing, when you drill it the hole has to be big enough for the FP, if you don't get the hole located correctly it will cause more F/P binding. BTW if the F/P is biding slightly even after the alignment issues are worked out, you could chuck it into a drill press and take a very slight amount off the rear where it passes through with a file, then smooth it with some emery cloth...basically a home builders way of turning it down.
On the F/P peening, it could be the hammer is hitting the F/P before its full stroke, which may be why the bottom edge of the F/P is peening. Like I had mentioned the best way to tell is with a window on the top of the B/C extension, that and some dye-chem on the hammer face may help. If thats the case you may need to make some adjustments...which there are a number of ways to deal with that depending on exactly whats happening (we can get into that once confirmed).
BTW I have noticed that many of the semi auto firing pins are somewhat soft and will peen from hammer strikes. I remedy that by home heat treating (hardening) the rear of them.
Here is a pic of a couple of my B/C's, the top is a Wiselite type, that had a window pre-cut, the bottom is a BRP "kit" type which I cut my own window in.
Re: No second shot
Good suggestions, thanks. Going to be spending some time on it tomorrow.
Re: No second shot
Alright, an update. Replaced the old recoil spring with a new, amazing how much more compressed the old spring was. Installed a new roller and stud, this time with a nice tight fit through the bolt. I also enlarged the hole in the stud to eliminate any binding on the firing pin. Created a window on the top of the bolt extension, and can see the hammer is striking nice and square with the meat of the hammer. Hardened the end of the firing pin, where the hammer strikes. Tightened up the wobble in the grip stick, and marked the hammer with blueing and found no place where the hammer is scraping on anything. I've got my fingers crossed, going to try to get up to the range tomorrow and see if I've eliminated the issue. Thanks again for all your suggestions.
Re: No second shot
Success! Got out to the range today and your suggestions did the trick. Didn't put a whole lot of rounds through it, enough to see if it was functioning properly. Was at one of our state ranges and they tend to frown on rapid fire past bursts of three. Next week I'll take it out to a private range and try to run a couple of belts through it.
Re: No second shot
Glad to hear you got it running.
Keep it lubed up good and run your loosest belts when you do further testing....run the same ammo too for a base line test.
You do know we like pics rights?
Oh and just so folks know in my above response I meant to say "assuming" rather than "amusing"...That's what I get for not proof reading my own post...lol. I just don't want to come off like I was acting rude, as it was my own dumb typo.
Good luck
Keep it lubed up good and run your loosest belts when you do further testing....run the same ammo too for a base line test.
You do know we like pics rights?
Oh and just so folks know in my above response I meant to say "assuming" rather than "amusing"...That's what I get for not proof reading my own post...lol. I just don't want to come off like I was acting rude, as it was my own dumb typo.
Good luck
Re: No second shot
No offense taken. And I will post some picks, especially now that I've got it running. Thanks again for your help.