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Hammer follow

Ask your build questions here. Welding, assembly, etc.
blackreichswehr
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Re: Hammer follow

Postby blackreichswehr » Mon Jan 16, 2017 10:14 am

that red circled area is ground down much to low. you moved your rails? look on this site for( pirates) bolt build.

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Der Alder
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Re: Hammer follow

Postby Der Alder » Mon Jan 16, 2017 6:08 pm

The below thread has a few pics of some of my semi hammers and B/C's related to what you are asking, showing both the hammer G/S mods and notice the semi bolt carriers I have pictured. The smoothest ones I have are the BRP type 2 (4th one on the right) and the modified BRP kit (3rd one) in which I scalloped the bottom of the bolt carrier...that one is smooth as butter charging. Which explains too why the BRP type 2 if you notice has the channel for the hammer which works well. The first 2 are older Wiselites BTW.

viewtopic.php?f=9&t=13480&p=96609#p96609

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Re: Hammer follow

Postby mtnlvr » Mon Jan 16, 2017 7:34 pm

Thanks for the replies guys.

Blackreichswehr...by "moved the rails" I mean put them where back where they should be. There was a few welds and a dent in the receiver keeping the recuperator from seating down in the receiver. This caused the left rail to be installed too high leading to top of the bolt carrier extension tube rubbing on the receiver. This has now been addressed by "moving the rails". The bolt now runs squarely through the receiver and no longer rubs.

The original lugs on the bottom of the bolt carrier had also been ground to that height when I got it. Looking around, it sounds like there is a lot of variation in terms of the height of the FCG and where the bottom of the bolt needs to be.

Der Alder, thanks for the link to your other post...very informative. Hopefully the OP got his anchor fixed.

It seems that I'm not that far off. It appears that my FCG is further away from the bolt carrier centerline and I need to bring the bottom of the bolt carrier down in the realm of ".060 further than the "bump" I already have.

What's the best way to add material to the bottom of the bolt carrier? Continue to build up a weld? Weld on a plate like Wiselite had done with some of theirs?

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Re: Hammer follow

Postby mtnlvr » Sun Jan 22, 2017 10:25 am

I reworked the bolt by welding a plate on the bottom towards the front of the bolt carrier and filing down the bump at the rear. The result is that the hammer, when held by the disconnector, only touches the bolt where this plate is, and has a lot more time to float and settle on the underside of the bolt before this raised surface has moved by. See pic.

Bolt-Bottom-Reworked.JPG


I went to the range yesterday morning and began loading single rounds into the belt. Fire, hold trigger, release trigger, listen for reset. I ran through a dozen or so rounds this way and not a single occurrence of hammer follow! :wnana:

Load 4 rounds into belt. First squeeze...bang. Second squeeze...bang, bang. :bang: Open top cover, eject forth round out of chamber. Notice a fairly generous indent in the primer of the ejected round. I look things over a bit and fire a couple more singles...no hammer follow. Load two rounds into belt. Squeeze trigger...bang, bang. :bang: :bang: Recover the two casings and one had a noticeably smaller primer indent.

So is this a firing pin bind condition or a firing pin inertia condition? Or just soft primers? I've been shooting PPU 8mm Mauser ammo (Serbian made by Prvi).

At one point I had added washers to increase the firing pin spring preload in steps until I didn't get ignition and I've been running with one less washer ever since so I woudn't think it's FP inertia.

I did notice some scuffing on the FP itself in the area of the wedge. Looking at the wedge, it looks like the hole was drilled out and there is a little mismatch in the hole like it was drilled a little off.

I also noticed that when I take just the bolt head and the FP, there seems to be a fair amount of FP wiggle up until the last ~.03" of fully seated which then it becomes pretty solid and doesn't take a lot of side load to bind. Should the FP be polished down a little on the first two diameters to increase clearance to the bolt?

How about the two piece firing pin? Is that something that can be retrofitted in the my existing single pin parts?

Baby steps. This rifle is awesome and has been a lot of fun to figure out!

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Re: Hammer follow

Postby Der Alder » Wed Jan 25, 2017 7:25 pm

Sounds like you are on the right track with the hammer follow.

The FP must move freely without any sort of bind. Sometimes taking emery cloth over it and polishing it helps...just don't get carried away and make it small as that will actually cause bind too...just go a little at a time and test. Make sure too it is well lubed.

These guns in semi can be very ammo specific in regards to primers. The type you are using, though I have not used so I can't comment on it as I still have a lot of surplus Romy. You could try too a heavy AR hammer spring from BRP which is needed for Yugo ammo due to hard primers.

My builds seem to be more temperamental in 8mm, but run reliably when using the .308 setup. If you don't have the .308 parts I recommend getting them if you can. NATO spec .308 is much more consistent IMO.

These guns in semi can be temperamental till you get them figured out. Everything from the tightness of the gun, to the booster size to the hammer spring, FP protrusion, bolt carrier smoothness, hammer profile, FP washers (sometimes), recoil spring lengths, etc... all combined with varied ammo types can make them a level 10 build...but if you take it one step at a time as you are doing you will get it.

Good luck...Keep us posted.

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Re: Hammer follow

Postby mtnlvr » Fri Jan 27, 2017 4:55 pm

Heading to the range tomorrow for another round.

As far as 8mm ammo, all I've got is current production PPU (which I'm beginning to think has thin brass and soft primers) and a case of Turkish ammo. I plan on trying some of both tomorrow even though the Turkish is said to be a no-no.

I do have the parts to run .308 and have some Lake City as well as some Russian steel case Wolf, TulAmmo and Silver Bear.

I polished the FP (and spare) also plan to try shimming / preloading the FP spring more along with the XP hammer spring to see if that stops the slamfires.

Are people lubing with oil? Or are there places that should have grease applied?

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Re: Hammer follow

Postby jbaum » Fri Jan 27, 2017 6:07 pm

PPU ammo is underpowered, so it likely won't give you enough recoil to operate the gun properly anyway. Turkish ammo is way overpowered, and is strongly recommended against using.

8mm has more power than .308, so use that (reloads, Winchester, Federal, etc.) instead of the PPU. This will give you the best chance of making the gun work reliably. Once that is accomplished, then you can tweak things to get it to work with PPU or others.

.308 works for some, and some never get it to work reliably. It will depend on the gun and how much friction there is. A light car chassis grease (in a tube) is what I use for rails. Other parts can use motor oil. The barrel extension only lightly lubed in the roller tracks. The bolt and trigger group ares lightly lubed with oil. The feed mechanism can be a combination of a few dabs of grease on the pivot points, and a few drops of oil elsewhere. Friction is your enemy with a semi, as there is very little extra power to lose to it before the gun won't work.
John@German<remove this>Manuals.com

http://www.GermanManuals.com

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Re: Hammer follow

Postby mtnlvr » Sun Jan 29, 2017 1:54 pm

Hammer follow arrears to be solved! This was the best outing with the semi MG42 to date. Not perfect, but got to run through a few different ammunitions and really begin to see how much a role ammo can play in reliability and safety.

From my last outing, I found another firing pin laying around that is around 28% lighter than the FP I have been using. I also clearanced another .015" off the bottom rear of the bolt carrier to give the hammer more clearance to the bolt carrier after the disconnector catches the hammer.

I took case measurements after firing (to the extent that I could...some cases were dented due to my bumper shifting) and compared to new ammo measuring in approx the same position.

Using 12.6mm nozzle, I started with some .308 or actual 7.62x51 NATO Lake City brass with a FMJ projectile. I'm unsure what exactly this stuff is or how old it is...my father has had it for some time. No functional issues. The only thing of concern was the cratered primers protruding .008" after firing. There's also a .003-.004" bend of the rim from the extractor and a fair amount of impression from the ejector. Shoulder diameter grew about .006" to .457". Case diameter near the head grew .004" to .473". I will discontinue the use of this ammo until I can chrono a round, maybe swap to a mil spec primer, and potentially reduce the charge if it seems like it's over pressured.

20170128_122425 (2).jpg


Next up, .308 Silver Bear 145 grn FMJ, zinc plated steel case, berdan primed. Again, no functional issues. Primer strike and flatness look good, no rim damage from the extractor, slight ejector impression. Shoulder diameter grew about .007" to .458". Case diameter near the head grew .013" to .473".

20170129_131728 (2).jpg


Next, swap bbl and feed tray to run 8mm.

First up, Turkish 8mm ammo. Like the Lake City stuff, I have no idea what this is, where it came from other than my Dad bought it some years ago. The round failed to fire...light primer strike. I may try this ammo again with an extra power hammer spring and the chrono as it has been mentioned that this stuff runs hot and inconsistent.

Next, The PPU 8mm 198 grn FMJ brass case, boxer primed ammo that I had been using. Slamfire! This stuff definitely seems to function the action well. The primer is well struck with an ever-so-slight bump in the bottom of the strike...possibly the beginnings of a crater. The rim is heavily damaged from the extractor, rim bend ~.010". There's also pretty significant ejector damage. Shoulder diameter grew .002" to .434". Case diameter near the head grew .006" to .466". I will likely try this ammo again with a heavier FP spring or increased preload on the FP spring and potentially extra power hammer spring.

20170129_131903 (2).jpg


Back to .308.

Loaded a round of Tula 308 150 grn FMJ steel case, berdan primed. The round fired but there was some smoke out of the action. Went to eject the spent round and all that came out was the case rim! The rim separated right at the forward edge of the extractor groove. I was able to extract the case using a tap and section of 1/4" dowel. Shoulder diameter grew .007" to .4575". Case diameter grew .008" to .471" after extraction. I don't think I'll be shooting this stuff again.

20170128_170858 (2).jpg


Bolt appears to be in good condition, extractor claw may have a slight crack in one of the "ears".

Does anyone have any feedback in regards to the common theme of extractor damage to the rim and rim separation? I did clean the chamber afterwords and it didn't seem all that dirty. Headspace? It wouldn't be a timing issue where the pressure is still high during extraction would it? Is it common to have rim damage in these rifles?

Would a larger nozzle for 8mm be wise since the 12.6mm nozzle cycles the 308 reliably?

Does anyone have a set of .308 and / or 8mm headspace gauges they'd be willing to rent out? If so, please PM me.

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Re: Hammer follow

Postby mtnlvr » Fri Feb 03, 2017 6:29 pm

Pretty quiet around here.

I checked headspace on the 7.62 x 51 barrel using .308 gauges. It checks good...the go gauge goes, the nogo gauge does not.

The 8mm is a different story. The nogo and field gauges both go in all three of my bolts. In fact, the field gauge goes with an additional .012" shim behind it with the bolt that I have been firing, and the other two both go with .010" shim behind it! It would seem that this barrel and extension is a bit long.

So the 8mm barrel will definitely be shelved for a while until I decide to pull the extension and correct the headspace.

But what about the hard extraction and resulting bent rims and separated heads on my .308 cases? Any ideas?

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Re: Hammer follow

Postby Der Alder » Thu Feb 09, 2017 4:38 pm

I've heard of Tula .308 doing that in these guns...I'd stay away from it in this platform. It may be fine in other guns, but not this one.

I'd try some different NATO spec .308 (7.62x51). If you find some South African or German NATO surplus, I'd try that. Stay clear of Indian .308 surplus. Oddly I've found Pakistani .308 to work well for me, at least the type that comes in belted cans as they still use the MG3. Here is a site that sells both Hirt and MEN in small quantities if you what to test it https://www.wideners.com/rifle/308-ammo Then what ever works you can stock up on.

Also you mention you have a chipped extractor, thats a cheap easy fix. You can use a .308 extractor as they are the same extractor as 8mm, but the extractor keeper and springs differ. If you don't have an extractor tool, get one as they make swapping them a breeze. Many times they come in M53 gunner kits.

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Re: Hammer follow

Postby mtnlvr » Fri Feb 10, 2017 9:15 pm

Thanks for the tips on the ammo. I will steer clear of the Tula...probably in all firearms, it's not worth it.

The extractor seems fine for now, I pulled it and cleaned it really well. I used a small vice grip to compress the keeper out of the way, seems to work well.

I dug out another 8mm barrel which seems to headspace well but the bore is heavily rusted. I soaked it and scrubbed it getting a lot of the rust out but the barrel looks pretty worn...almost looks like inverted rifling?

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Re: Hammer follow

Postby Der Alder » Sat Feb 11, 2017 3:01 pm

On the Tula ammo, just to be clear, I don't have a problem with Tula in *most* platforms. I use it as cheap 'blaster ammo' in AK's and even AR's...I just don't recommend Tula .308 in this platform as read many complaints from blown primers to head case separation as you have found. Seems Fals have issues with it too from what I've on other forums, but I have used it in my CETME's and HK91 without issue.

On your 8mm barrel, if it cleans up ok I'd use it so long as the chamber is decent and it headspaces ok and the rollers fully lock (you can read more about that in the stickies here). A lot of us use worn 8mm 'blaster barrels' now that good barrels are pricey with the 2005 ban.

Pitted and worn yugo 8mm barrels in these semi M53's may not be optimum or accurate, but again in this platform so long as it is safe I'd use it in semi beltfed as all I need it to do is go bang and poke holes in paper (even if it looks like a shotgun pattern...lol).

On the cratering of primers...I see that sometimes in my builds (ammo dependent) and it seems to be the nature of some ammo in these semi converted guns. I even see it my 9mm semi converted Uzi's and Sterling's sometimes. So long as its not blowing primers or piercing them I would not worry about it. Again, sometimes its just a matter of finding what ammo works best and once you find that, stock up on it. Which is why I'd try many types of surplus till you find what works best.


All that said, I really don't not think you have a problem with the gun so long as FP protrusion is correct (only you can check that), IMO it's more of an ammo issue from what I'm seeing in your pics IMO.


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