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Discussion Starter #1 (Edited)
Hey guys.

For starters, I did try to search on here for this. I found some info, but not any details or anything like that. All I could find was a few "they are the same" and a few "No, they are different, something about cocking tube relief" but no pics or anything showing any differences. To be honest and upfront, these are relatively new to me.

I have a few barrels and trunnions here, and ultimately would like to build one MP5 reverse stretch. I'd just like to know what exactly these parts are, and would love some opinions on which would be the better one to use.

* Neither trunnion is marked.

* One appears to be "new" (Right), the other was previously built/used (Left).

* There are notable differences between the two;

> (left) One has what Im guessing is some kind of "magazine" tab/relief there

> The (right) one appears to be beveled(?) on the inside part where it looks like the rollers enter, the (left) one is not

> The (left) one has raised "ears" where the cocking tube would go, the (right) one does not.

Here's some pics;







Would either of them be suitable for a MP5K/Reverse stretch build? Or is one better suited vs the other? Im seeing some pretty noticeable differences in the machining and angles of certain areas on the trunnions etc.

I have collected some "K" front end parts and a Speshul Wepunz receiver. I can see that I will have cut some of the top portion of the receiver off for the cocking tube, but wanted to get the trunnion figured out so I can start moving forward on it.

Any help/info is appreciated. Sorry if its a noob question.

NK
 

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Discussion Starter #3
I do not have a BCG yet.

Was really just more curious as to the differences in machining between the parts, and if one is "better" than the other. Or if maybe some of the differences (the "ears" where the cocking tube goes) are the difference between a MP5 and a "K".
 

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Neither one or what you would say MP5K trunnion that was the issue with the special weapons parts it wasn't till Rim country developed and put out a true copy of the MP5K trunnion. In the past before the MP5K trunnion was made
Manufacturers would just remove the bottom side of the cocking tube sleeve. If you're seriously looking at building a K gun or reverse stretch. I would suggest getting one of Rim countries k trunnions and start out the right way so then you can use Factory cocking tubes without any modification and everything will fit properly.
 

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Discussion Starter #5 (Edited)
Neither one or what you would say MP5K trunnion that was the issue with the special weapons parts it wasn't till Rim country developed and put out a true copy of the MP5K trunnion. In the past before the MP5K trunnion was made
Manufacturers would just remove the bottom side of the cocking tube sleeve. If you're seriously looking at building a K gun or reverse stretch. I would suggest getting one of Rim countries k trunnions and start out the right way so then you can use Factory cocking tubes without any modification and everything will fit properly.
K, Thanks! If neither is ideal I will look into the right one.

I am just curious though, what the physical difference is between a regular and a K trunnion. The ones shown on HKparts I was looking at do not show the "top" parts of the trunnions, only the bottoms. So there really is no reference to actually "see" the difference in the parts. For learnings sake.

Ill be grabbing a new trunnion then. Thanks all!

(Edited to add)

Found a pic of the MP5K trunnion online, and now see the difference. Understood. Thanks all!
 

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Discussion Starter #6
After looking at the options there, I have one more thing that I gave a little thought to.

I have several barrels and trunnions here, none of the trunnions are MP5K type though.

It appears to me anyway that I could machine/modify the "channel", for lack of better term, on the top of the trunnion to better accept the proper cocking tube parts.







Would opening up the area to allow better cocking tube fit be good enough? It looks like slowly removing material and checking fit could work out.

It seems to me that it would better than molesting the cocking tube assembly. I have enough trunnions on hand that I won't be sad if I mess one or two up trying. At that point I'd just buy another (proper) one.

Otherwise I have a handful of trunnions with no purpose.
 

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Honestly something you can do with a Dremel.. Other option is use a special weapons type cocking tube, my first home build has this.
 
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