Recoil Nozzle play

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Breakout703
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Recoil Nozzle play

Postby Breakout703 » Tue Feb 13, 2018 10:07 am

I finally bought and received my parts kit and I received my new front receiver bushing from BRP. When I screw the flash hider onto the new bushing (with the recoil nozzle) the flash hider bottoms out on the threads before it touches the shoulder and the recoil nozzle is loose. It probably has about 1/16" to an 1/8" of play.
Recoil_Nozzle_play.jpg

Dimension "A" is the play I'm describing. with the flash hider screwed on the recoil nozzle rattles back and forth. Also the flash hider is about the same distance from the shoulder, Dimension "B". the 13mm dimension is one I have from a build tutorial. So my question is should the recoil nozzle have any play? I feel like I have to turn back the face of the threads to take out that play and also turn down the face of the shoulder so that the flash hider indexes properly with the flash hider locking detent. My next question is does that flash hider contact the shoulder face or do I just need to worry about taking out the recoil nozzle play and indexing the lock detent. Thanks in advance for your help. Also, I HAVE searched forums and could not find any posts that describe this same problem. So if you tell me to search the forums then please tell me the search term to use.

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Re: Recoil Nozzle play

Postby oakrodent » Tue Feb 13, 2018 8:27 pm

sound like there isn't enough threads exposed for the booster. Is your overall length correct? M53 is also longer than a MG42. You are also putting to much thought on the booster. There should not be any play in recoil nozzle. Once everything is correct, you screw on the booster until the recoil nozzle touches and loosen it a little. Too tight will cause issues when everything heats up while shooting. I acually had some very intresting chats with WW2 German MG42 gunner. He told me the first time he saw combat was against the Russians. They were already defending. The Russians attacked their line early one morning. He opened up his 42. Shortly after the first can the gun stopped firing. He noticed the booster lock had been damaged and the booster assy had unscrewed and blown off. He got out of his trench & had to crawl around to find that damb booster! He found it down range , quickly screwed it back on and and smashed the lock down! Just amagine this poor kid crawling around in the dark, under attack & trying to find these parts in the snow! I have accualy had a booster unscrew its' self while shooting a MG34. It was supprising how far it went and I found it still all together. The beauty of the 42 is it's simplicity.
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Re: Recoil Nozzle play

Postby JBaum » Tue Feb 13, 2018 11:37 pm

According to the manuals, the booster gets screwed on tight, then backed off just enough for the detent lever to drop into the first available slot.
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Breakout703
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Re: Recoil Nozzle play

Postby Breakout703 » Wed Feb 14, 2018 8:09 am

Oak, you asked me if my overall length was correct, what length are you asking about? The length of the bushing? I don't have the aft part of the receiver welded up yet. I was just checking fitment with the bushing and the booster (flash hider) doesn't screw tight against the nozzle and the play seemed a bit much, it rattles around if you shake it. So it sounds like there should be less play than my parts have. Here is a pic I took when I was playing with it
20180212_180450.jpg

In the picture you can see the booster is around 3/16" from the shoulder, you can almost see the threads on the bushing. I COULD chase the female threads on the booster a little deeper if I had any idea where I could find a tap this size. So long as no one else rattles loosely, then I'll turn those threads down till I can take most of the play out.

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Re: Recoil Nozzle play

Postby robertmcw » Wed Feb 14, 2018 9:15 am

I just saw your front receiving bushing and I would not use it. It just looks wrong.
That looks it is the US made not the Rheinmetall one.
I think I remember reading one of the posts, one guy used the US part with his build and it was not in spec and he said it was not heat treated as well so he would swapping it out with a Rheinmetall one.
Did plan to use a MG3 Barrel Bushing of plan you use an 8mm Barrel Bushing? If you decide to put a new Rheinmetall front receiving bushing in, I think the barrel bushings have different lengths. I would think you want to build it so you could use both caliber ammo.

I would call the guys at BRP an ask what they guys think.

Event. I would not be a happy camper.
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Last edited by robertmcw on Wed Feb 14, 2018 9:43 am, edited 1 time in total.

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Re: Recoil Nozzle play

Postby JBaum » Wed Feb 14, 2018 9:37 am

If you got the part the booster screws onto from BRP, what did they say about the fit?
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Re: Recoil Nozzle play

Postby Breakout703 » Wed Feb 14, 2018 10:23 am

I sent a message to BRP (where I bought it) we'll see what they say. RTG has new and used rhinemetal bushings, maybe I should have just gotten those. I didn't see any complaints about BRP parts though. I could put the calipers to it but I haven't seen any dimensional data or drawings for it. Here is a pic of the parts before I put them together. Does that bushing look wrong?
20180212_180401.jpg

I was looking at the rhinemetal versions and I noticed (other than the different shape of the rear end of), there is a notch in the threads mine does not have. Is this important? Oh and yes, I would like to be able to shoot this in 7.62 and 8mm, but I have not found any conversion kits available right now so it will be 8mm at first. If it ends up not shooting 7.62 then oh well, not that big of a deal for me since I mostly reload.
rtg_rhinemetal_bushing.jpg

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Re: Recoil Nozzle play

Postby Breakout703 » Wed Feb 14, 2018 6:04 pm

So the issue was thread erosion. I think the flash hider was just indexed a little different from my bushing and the gases did a number on the exposed threads. It stopped pretty solid so originally I thought it was stopping against a shoulder in the flash hider. After a little inspection I saw that wasn't the case so I worked the damage threads into submission with the bushing. No mods necessary. Thanks for you replies.

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Re: Recoil Nozzle play

Postby JBaum » Wed Feb 14, 2018 7:55 pm

rather than erosion, it sounds more like the threads were packed full of crud and it just needed cleaned. Glad it worked out, and the little notch showing on the front of the threaded end in the picture is irrelevant to anything.
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Re: Recoil Nozzle play

Postby Breakout703 » Thu Feb 15, 2018 8:53 am

If it was just crud, it was baked on hard, I let those parts soak in mineral spirits before taking a brass brush to them. Thanks again for answering my question.


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