Interesting day at the range

[gunslingerdoc]

Yesterday, I managed to escape the grasp of pregnant women at noon. Grabed the mg-34 and the mg-42 with repostioned FAL FCG and Pirate inspired fp design. 308 for the 42 and 8mm for the 34.

Previously, I had no problem poping primers in the shop, but no success with live ammo since I 'imporved' my extension and FP set up using the wedge with a hole in the back and stock FP (copy of Pirates set up). I decided to use a stock FP, but I would drill the wedge all the way thru, letting the stock FP float and using my FP to strike its base for ignition. It worked like a champ with primers only. I did keep a spring to hold the FP off the base of the wedge. OFF to the range - I was pretty psyched.

My FP conisted of a 3/16 drill rod and I found some nice aluminium tubes about 3/8 ling to use as spacers - I drilled 1/16 holes and used roll pins to secure them. After 2 rounds, the aluminium crapped out on the rear spacer so I turned down some other drill rod and migged it in place of the rear spacer.

So the first 2 rounds went well. the second 2, I had to convince the bolt to move forward a bit but then 2 shots went off with out a hitch. Now on to 4 rounds in the belt.

THings got exciting here, I had all 4 go off rapidly. I ended up with 2 split cases, an hand full of hot powder, a bullet stuck in the barrel, the back half of a case flatened (like those exploding cigars in th cartoons) stuck to the bolt face, and a new sense of security in my welds (nothing broke). The barrel gate had come open and my 'new' firing pin was bent.

I went into my partners shop and restraitend it and discovered the front spacer (I left the aluminum one since it only had to retain the spring from sliding rearward) had moved and hence allowed it to impinge on the rear of the stock FP --- welcome to slam fire out of battery central. I then pulled out FP #2 and had to shorten the tip to keep it off the stock FP. I fired 10 rounds singley, then I got a double. I decided temping fate again would be stupid, so here ended the 42's day.

The 34 ran pretty well except for a few FTF's, but I hadnt cleaned it since I got it and it was a touch dry lubrication wise.

Im waiting on my partner in crime to email me the pics he took of the 42 implusion - I think I was very lucky! I'll post them for your amusement when I get them.

I had no issues with the FAL FCG - it runs, even full of metal /grinder dust and unburnt powder. I need to get a safe FP set up to really torture it. I added weld to the inside of the grip stick before I drilled the hammer and trigger holes, so Id like see how they hold up to extended firing. At least Im back to a gun that goes bang. I think Im going to weld a stock FP on to an extension and call that good. I know its not 'cool' but I think it will be reliable, and we know its a proven design. While Pirate is having good luck with his extension/FP/wedge design - Im not.

I may try using a 45 ACP firing pin type spring on the front side of the stock FP and an extension thats spring loaded rearward, but I think Im just adding more parts - which generally aint a good thing with respect to reliability.

Will see, right now I just want to get to Pirates point of several belt testing!

[Pirate]

GSD,
some suggestions:
mark the bottom of the gun with magic marker for a refrence point to show the bolt is
fully home, check this before every shot during inital testing to prevent firing from a
bolt that is not fully closed.

the length of the striker is critical, with the bolt in the gun check to see where the hammer
face is and cut the striker to that length. if it is to long even by a little it will fail to work
properly

the spacers should not touch the ejector bar, it will cause binding.

the striker I am using goes through the wedge. if you copy it exactly and fit it properly
it will work.

lube the bolt parts well, I use GI LSA

[panaceabeachbum]

So the first 2 rounds went well. the second 2, I had to convince the bolt to move forward a bit but then 2 shots went off with out a hitch. Now on to 4 rounds in the belt.

I wonder if the pressure needed to get the bolt into battery was the firing pin sticking out of the bolt face slightly, bieng pushed back into place ? just curious. Have you relieved the buffer screw so it doesnt contact the firing pin at the end of the recoil stroke?

[gunslingerdoc]

Well, I finally finished stage one of the master bathroom remodel and was allowed to escape - unfortunitely it was close to dark and the new rules prohibit firing after dark so I had little time.

I was using a new FP where I welded a stock FP onto a length of 3/16 drill rod. I have a rear spacer the bears against the feed stud and a front spacer that just serves as a base for a spring that keeps the FP loaded rearward.

10 rounds single - no prob. Then I moved onto 2 round groups in the belt. I got thru 12 more rounds and had a double. Since it was dark and didnt want the sheriff called on me again...I decide better stop for the night.

But I think I figured out a new problem (or one I may have had earlier, but didnt know).

Im not using a feed stud with a hole for the FP. Im using the top half that I broke when I tried to drill thru it. I added a bead of weld to the bottom and dremmelled a concaved groove on the bottom for the FP. I also welded the feed stud to the bolt extension after I dropped, lost, and found it 400 times.

Interesting enough if the spacer moves in front of the ejector collar and jams itself there you get a fixed firing pin.

So I need to better secure the FP at the rear. I really dont want to play with another harder than diamond frigging feed stud, nor do I want to scavenge one from an otherwise complete bolt. I think I'll turn down some rod, drill a hole and weld it in for the bottom.

Yes, I know its crude, but this is my prototype bolt and I'll redo it after Im sure I have a working gun.

Im half way to the pirate testing benchmark - a whole belt! And I still have all my parts..

[gunslingerdoc]

Here are the pics of the of the results of both an out of battery explosion and I suspect a firing pin sticking.

[TOM R]

you are real lucky, i hope you wear heavy leather gloves and a leather smock when doin these trial shots,would suck for a doctor to blow off his own fingers

[gunslingerdoc]

Yeah, real lucky came to mind after I verified finger/hand integrity! Actually I was using a small hammer to pull the trigger. Funny how my buddies kept getting farther and farther away as we tested it. I think they were flinching worse than I was after the little explosion!

I noticed today that my barrel latch was popping open. Closer inspection revelled it is bulged outward.

I did get 27 rounds at lunch with only one double, so Im getting closer. Seems the minute you fix one thing there's another problem you discover.

[Pirate]

GSD, that was a bad explosion, personally I would deem the gun unsafe to shoot untill it has been
properly repaired and inspected. you are putting your safetey and those around you at risk trying
to shoot a gun that is not ready to be fired. the true definition of a "working" gun is one that not only
functions but is safe to shoot. by rushing the build you may wind up at the local er with a bloody towel
wrapped around your hand and 2 or 3 of your fingers in a baggie in your hip pocket.
when working with the bolt / firing pin, the parts need to be perfect, a bodge it to work
approach will only lead to disaster.
if the striker firing pin binds it will cause an out of battery detonation. a welded together
fp is dangerous a it will not be totally concentric and straight, causing binding. that was one of the
reasons I went to a 2 piece striker arrangement. a one piece pin has proven to be reliably
unreliable. at this point in time I have fired oaver 500 rds of .308 with no problems, and 2-3 hundred
rounds of 8mm, with a few misfires. at this point I have made a few changes and should have eliminated
the problem with 8mm
This build is not like an ak or ar 15 that you can put together in a few hours and shoot. It
is a complicated restoration project with modifications to the bolt and gripstick that need
to be done precisely and properly to work. as a professional machinist / welder / fabricator I can't
stresss enough the importance of taking your time and doing it right.

[gunslingerdoc]

Pirate,

I cant agree more. I did xray the receiver when I finished welding it - Then I went over a few spots and re x-rayed it. I x-rayed it again Saturday and there was no change. From a weld standpoint I think Im Ok.

Now from a Firing pin - whether floating factory with extension (like yours) or a one piece - standpoint, Im at a dangerous spot. I can design it, model it, and get it to work dry. Even creating conditions that seem impossible I cant induce a malfunction - when I have I fix it. However the reality is Im still getting slamfires. I tried again tonight using your system and I got another double. THe second case looks good (ie not blown out or overly out of shape) so I think it must have happened with the bolt very close to fully closed.

Im doing all my testing of the 'pod now and using a stick to hit activate the remote fire, but its still scary when it doubles. Im concerned I may be getting a bump fire type situation. Truthfully, after tonights testing using an even heavier spring behind the wedge, Im stumped. I may try a new wedge and feed stud and see where that leads.

At this point I have a working FCG and welds that are good. My bolt extension seems to be getting the job done even if its ugly - like you I want to get the wrinkles worked out before I spend time on pretty - but my firing pin situation and its interaction with the bolt, feed stud and or extension is an accident waiting to happen. Bad part is Im now at a point where I dont know where the problem is and that really makes me nervious.

I realize this is not an AR or an AK - but then again, I have gotten lots of $ from folks that cant build sub 1/2 moa AR's or m1A's which takes some time and some skill. Granted Im not working with old parts, from different countries and converting an open bolt gun to a closed bolt gun with no good dimensionally referenced drawings (bothers the enginerd in me). I think the Mg-42 is going to be put on hold for a bit until I think about for a while (the wife will be happy, I can get the batheroom tile done!) and hopefully see some other sucesses.

[Pirate]

GSD, check your fcg, you said you cut the sear spg, it may not be working properly.
lube the inside of the bolt and firing pin. with the gun assembled, ,and gs out push
fp forward and seee if it returns by itself. if it binds polish it down till it moves freely.
look for rub marks on the parts.
After I had my out of battery detonation I marked the receiver with a magic marker
to show the bolt is home and locked. and checked before every shot. the event you
had was the worst I have ever seen in 40 years of shooting, you are really lucky
you didn't get hurt.
I have been doing this a long time and when I got lax and in a hurry I had a problem.
it was a wake up call to be more carefull.
basically it all boils down to a part being a few thousandths off that will give you
problems, keep checking how parts fit and suddenly you will discover the problem, solve it
and it will all fall into place.

[gunslingerdoc]

Pirate,

I think you may have the right idea with the FCG. Im going to check that out tonight/tomorrow. I really cant find anything wrong with the mechanics of the FP set up. Of course since I have yet another bent pin/extension I'll be making another. I did manage to get the one piece welded perfectly straight on to the extension rod though with crazy clamping, small wire, and lots of luck - just for the reason you mentioned. I really wasnt too enthused about it though because I know I would have trouble getting another that straight.

On my last range trip, I was using the 2 piece method because I was worried about the longer one piece pin binding. For the life of me I cant fathom how the the 2 piece set up I have will cause an out of battery explosion - mechanically, it just cant be. No matter how much I twist, push or torgue the parts I have no binding that will cause the firing bind to stick and create a slam fire. There is NO way I can see for the extension to bind and fix the factory FP.

Ive been in the mode of find one problem, fix it, correct whatever side effect of that fix , etc. I think you suggestion about the FCG being another place to look is a good plan. I do have a bar welded across the rear of the trigger to keep it from moving too far and that is intact, but a sear engagement issue is certainly in the realm of possibilites. Best part is this is my 'improved' grip stick and I spent much more time being extra careful - Murphy's law is that will be where the problem lies.

Too bad I have a soccer game and a welding class tonight - maybe Thursday.....