Marushin MP40 - Loose Trunnion???

My ABS Marushin MP40 (bought used) has a loose trunnion...The barrel screws in fully & locks up OK, but I can see the trunnion wobbling around a bit...

I can see what appears to be a pin going through the magazine housing, receiver tube, and trunnion...Does it drive out or is it cast into the plastic???

I was thinking that if the pin drove out that I could epoxy the trunnion into the receiver tube...And then pin the rest together...

Thanks for your reply, Cerwyn!

Can you suggest a source for the parts??? I have had limited success communicating with TTD...The upper with trunnion seems to be all I need for that one...

I also need an upper receiver for my Nakata MP40. It has a zinc upper receiver, and for whatever reason, the previous owner ground the three locking lugs (on the rear of the tube) away...Possibly because the lower seems to be oribinal MP40 [marked BNZ 43]...Which means I may also need the lower receiver for the Nakata...

Your nakata to my knowledge has no locking lugs on the rear it is held in place by the locking pin, at least on my nakata there there are no lugs on the rear of the upper, if your lower is from a real 40 then you will have problems as they are a totally different size.As for the marushin i would take cerwyn up on his offer and get a new upper and perhaps the lower but does this wobbly trunnion cause any problems in firing it? if not is it a real problem to you if not i would not worry too much there are few modelguns that have wobbly parts on them but as long as they fire well we put up with it.

claymore wrote:

Your nakata to my knowledge has no locking lugs on the rear it is held in place by the locking pin, at least on my nakata there there are no lugs on the rear of the upper, if your lower is from a real 40 then you will have problems as they are a totally different size...

Here's a pic of the Nakata -





My Nakata upper has definitely been ground, and squeezed as well...



Lower looks original/'real', is steel, not zinc, and has period markings plus waffenamt -



Unfortunately, the previous owner (supposedly a prop company) has cut approximately 1/4 inch off the front of the lower...And it now secures with a screw instead of twisting under the magazine housing...



It had sawed-off pieces of drill rod [inch sizes, not Metric] in the trigger mechanism, which made it very sloppy; I have replaced those with Metric pins. Much better, but the zinc sear and bolt have worn engagement surfaces making it 'hair trigger' (if it engages at all). I'm working on a new sear [steel].

The screw securing the lower makes field-stripping a chore, as the knob for the lock has to be removed to remove the one-piece Bakelite foregrip before that can be removed to get at the screw...I'm debating on whether to weld a curved section to the lower to extend it under the magazine housing as was originally intended...

Edit: Forgot to mention, boltface is heavily indented where bolt has been banging into the chamber insert...But the insert/chamber and detonator look unused...

Cerwyn wrote:

I can help you out with an ABS Marushin MP40 Upper Receiver. It's worth checking the locking lugs that hold the receiver and retaining ring of the lower for wear. If yours show signs of wear it's worth replacing Lower and Upper Receivers as a set (I've Lowers too if you need one)

Cerwyn -

Got your PM; thinking about it now...My upper & lower locking lugs look excellent; no discernible wear. I have to wonder about the upper; rear sight seems glued on, magazine housing looks separate but I don't see any way to separate it (I can slide a slip of paper under the curved section of the housing so I know it was a separate piece). I can't see anything holding the trunnion in place...but it is definitely loose, I can wiggle it all around...I can slip a .002" feeler gauge around the trunnion except where that plastic 'pin' is in the front of the magazine housing; there is *something* where a real pin would be, on each side...there also seems to be a lip at the top and a ridge at one side...Possibly it was inserted from the rear??? Down the tube and maybe snaps into the front end???

Just broke the feeler gauge, but I can insert it around the magazine housing and the upper receiver in most all areas; but there are a couple areas where it hits something...I'm thinking it was snapped into place as well...And not readily removable...

BTW: The Marushin came with what appears to be a 'real' MP40 magazine...All steel; spot welded follower; manufacturer markings...I don't think a modelgun manufacturer would put waffenamts on the side of the follower or the underside of the baseplate, where they can't be seen unless disassembled...





The Nakata came with what appears to be a 'real' Sten gun magazine...(No picture, as it has no markings)...

Cerwyn wrote:

I believe that STEN magazines fit Nakata MP40 models nicely and work well, possibly after the same spring and feedlips mods'. It's a gun/mag combination I've seen here before.

Here's the magazine that came with the Nakata -

Quote :

Marushin supplied new spare upper receivers as one piece with the trunnion and magazine well fixed in place. It certainly looks like they're intended to be removeable. My own ABS Marushin '40 has no gap between the well and receiver. I don't know for sure but wonder if the older versions did have removeable parts

Here's the Marushin magazing housing & receiver w/feeler gauge, and trunnion w/feeler gauge -





I'm hesitant to try to force them apart from the receiver tube...I don't think there's any glue involved, but this old plastic/ABS may be brittle...

Has anyone broken an upper receiver and posted pics???

Edit: The Sten magazine is a poor fit in the Nakata - It barely goes in all the way, and the catch doesn't quite engage...The German magazine has the cut for the catch .058" deep; the Sten cut is only .030" deep...