Is my semi MG42 supposed to be making this noise?

[ScottD]

Hola amigos, its been a LONG time since Ive posted here. I built my MG42 almost 10 years ago and it doesnt get much use. The other day I took it apart to touch up some bluing on the receiver. When I put it back together the bbl gate was a little harder to close than I remember. (It now takes a firm SMACK)...but heres what I DONT remember it doing.....when I charge the weapon, as soon as the bolt head pulls away from the bbl, the recuperateor (think thats what its called) smacks the bbl forward with a very audible noise. Its a lot more violent and louder than I remember. Is this normal for a semi gun? (Again I apologize, but its been 10 years or so since I built this gun......semi plans were still in their infancy back then)

[HKARAK]

Mine does same, so have to say yes

[JBaum]

I'd check the front barrel bushing for sticking. The recuperator should slap the barrel forward, as it has to immediately after the bolt head releases. But, if the barrel is sticking somewhat, the recuperator is pushing until it overcomes the sticking and then the barrel slaps fully forward after a slight delay. That would explain the barrel gate difficulty too.

You've noticed a change, it's time to look for the cause.

Check the front end of the barrel area for rust/corrosion/fouling.

[ScottD]

Everything looks fine, everything moves freely. Ill take another look again tonight.

I dont see what all could have shifted from a simple disassembly, but stranger things have happened.

[www.Prussia.us]

Okay here is a super stupid thought, if all was fine before-and since these parts develop their own unique wear spots, could it be possible that your barrel is re-installed upside down so the barrel block side is facing up which was previously facing down?

This is not a functional issue, but on a re-welded custom-fitted semi, might it become an operational issue??

[DARIVS ARCHITECTVS]

YES, this sound is NORMAL. As you draw the bolt back, you are also drawing the barrel back until the rollers encounter the camming piece, whereupon they are forced inwards, unlocking the bolt from the barrel locking piece. Once free, the barrel can return to the forward position under the force of the recuperator while you continue pulling the bolt rearwards.

Ever notice how the charging handle is designed for maximum leverage during the first 1/4" of drawing the bolt back? That's because you need such a large force to pull the barrel AND bolt against the force of the recoil spring AND the recuperator, until the barrel is released. Then you only have to pull against the recoil spring.

Once you understand how ALL the parts inter-relate and what they do, you can appreciate how truly elegant and simple the MG-42 is. It's a marvel of engineering.