8mm Romanian surplus

[Sw1ngK1ng]

I recently finished building my first mg42 and was told to only run Romanian surplus or commercial ammo through it. It seems that there are two variants of the Romanian surplus and the kind I have is giving me issues. Powder and dimensions seem good but I am getting very inconsistent primer strikes. The firing pin will punch all the way through the primer one time and the next shot will be a light primer strike and fail to ignite. A second issue I am having is even with the booster removed and the flash hider backed as far out as it can be without falling off the action still cycles. It doesn't sound like an issue but it doesn't leave me with any room to adjust my gas pressure down. Lastly if anyone here knows exactly what steel the mg53 bolt carrier is made from I would love to know so I can re-heattreat it.

This is the Romanian surplus I have; http://www.sportsmansguide.com/product/ ... id=1522857

[JBaum]

Is your gun full or semi auto?

This isn't what you asked about, but I do have to ask. Why would you even try to run the gun with the muzzle booster partially unscrewed? It is not a gas pressure adjustment. If you've been reading the US government book on the MG34, it is totally wrong about saying that the speed of the gun is adjustable by unscrewing the booster. It's wrong about other stuff too. Out of 18 manuals I've translated for the MG34 and MG42, not once have I found anything about unscrewing the booster for any reason other than cleaning.

If you wanted to reduce the gas pressure, you'd put a bigger hole in the nozzle, but I don't know why you'd want to do that, unless you got one with a really small hole and the gun is recoiling violently. It is not a single shot that you have to recock/reload every time, and there's nothing other than taking off the booster that would achieve that goal. Even then, the bolt and barrel will recoil somewhat.

[Sw1ngK1ng]

It is semi-auto. If the flash hider is not meant to be unscrewed then why dose it have notches for that arm that comes from the front site to hold it inplace all around it? And as far as I know the booster has no threads to loosen or tighten. I did drill my booster to 12mm from 11.5mm but it made no difference. With the flash hider loosened as far as I can it operates very smoothly but when it is tightened as much as it can be it recoils very hard and even mashed one side of my ejector. I have not read any manuals, I have only done what mechanically makes sense.

Just to ensure I am not misnaming parts, this is what Im referring to as the booster;

And this is what Im calling the flash hider;

[JBaum]

flash hider = muzzle booster it's two components of a single part.

The other part is the nozzle.

Perhaps this exploded view with a list of all the names of the parts will help you:

viewtopic.php?f=39&t=3904

"If the flash hider is not meant to be unscrewed then why dose it have notches for that arm that comes from the front site to hold it inplace all around it?"

So that the threads on both parts don't have to be indexed so that when it's screwed on tight, the lever will fit in whatever slot is closest and the recoil booster won't unscrew. It is not an adjustable recoil system.

I never saw a gun recoil so hard it damaged an ejector. They're hardened steel.
Did you cut down your recoil spring just enough to where it allows the ejector button to hit the buffer without the coils being jammed together, or did you build it with the longer receiver?

[Sw1ngK1ng]

I used the new semi auto spring from brp. I also built it to the drawings that brp has but mine came out 1/8in. shorter. I was thinking about making a new ejector that is just short enough to not interfere with the casing until it ejects it and then trimming it down until Im happy with the ejection. I would making it out of something I can heat treat as well so its not soft.

So if the only adjustment is though drilling the nozzle, why dose it still recoil hard when the nozzle is removed with the booster tightened down all the way? Fyi Im naming the parts to what they are on the diagram now since I had them wrong.

[JBaum]

The ejector should not interfere with the cartridge now. If it does, you have a problem. The ejector button on the back of the bolt hits the buffer when the bolt recoils. That makes the button bump the ejector bar (inside the bolt housing), which pushes on the ejector to eject the empty shell downward. Until that happens, the front of the ejector should be flush with the recess at the front of the bolt head. It should not stick out at all.

I have no idea about what is going on with the recoil. I have a full auto MG42, and don't mess with the semi version. Someone else will have to join in here, but they'll want to know what receiver you're using, whose bolt, and whose trigger group as a start.

[Sw1ngK1ng]

I used the brp stamped sections and built it myself. Made my own trigger group because the brp one placed the hammer too high so i lowered the mount holes .07in. And I used the brp kit to make my own bolt carrier semi-auto.

Just checked my ejector and the center is flush with the bolt face when in battery but the top and bottom edge are rounded off pretty badly but before the hard recoil I had after tightening the booster it was flat, then I flipped it over after a few failed ejections and another hard recoil rounded off the other side. What I really don't understand is if the size of the hole in the nozzle is the only adjustment I have then why dose it recoil the same with the nozzle in as it dose when its removed?

My biggest question is in regards to the Romanian 8mm. Iv been told by many that it is some of the best ammo for these guns but Im worried there is more that one Romanian 8mm. The stuff I have was manufactured in 2013.

[Sw1ngK1ng]

Just checked my recoil spring. When the bolt is in the full rearward position there is 1.5 times the thickness of the spring wire left between the coils. Im not sure if this is correct but if it is supposed to be tighter I can make a spacer to go behind the spring. Again I am using a recoil spring from brp.

[JBaum]

I'm confident that Brian knows how to make a recoil spring with the correct specs. The fact that it doesn't look like the original when compressed would be irrelevant, as function and appearance are not necessarily related.

I'm not an engineer, so giving my thoughts on the recoil system and exactly why it works the way it does is not something I'll do. I don't BS or make stuff up about the way I THINK it might work. I share what I know, and admit what I don't.

[Sw1ngK1ng]

I don't doubt that the spring is wrong, if anything my receiver would be. Im not an engineer either but I think I can figure this out soon if nobody else can. Thanks for all your help!

[hakentt]

That ammo is junk. When people refer to Romanian ammo they mean this ammo http://www.aimsurplus.com/product.aspx?item=A8Rom

In fact just use newest stuff

http://www.aimsurplus.com/product.aspx?item=AP8FMJ198

[Sw1ngK1ng]

That ammo is junk. When people refer to Romanian ammo they mean this ammo http://www.aimsurplus.com/product.aspx?item=A8Rom

In fact just use newest stuff

http://www.aimsurplus.com/product.aspx?item=AP8FMJ198

What about it is bad? Is it hot, inconsistent primers or dimensions?

[hakentt]

Is it hot, inconsistent primers or dimensions?

all of the above, it is well known.

[Sw1ngK1ng]

all of the above, it is well known.

Well I guess I should have waited before drilling my nozzle to 13mm then lol. My mg is very smooth though so I think I will still be ok. still want to shoot the 200 rounds I have left though and keep an eye on a weld that Im not too confident in so if it survives another 200 rounds of this it should be ok to shoot better ammo. I don't want to pump more heat into the receiver if i don't have to.

Is there a current procedure for heat treating the bolt carrier? I don't feel like there is since I can't find any info on what steal it is made from.