MP5K-SD

Legalese: It is perfectly legal to build a gun for personal use as long as it is legal for you to own.  There are caveats to building deactivated formerly fully automatic firearms.  I will try to outline them as best I can.

 

Somewhere in late 2017, after many months playing with a DI 9mm AR-15 it still was not at the level I was happy with.  I began researching other semiauto action types again and circled back to the venerable roller lock action.  I like most had at least a passing interest in the MP5 but could never justify the pricetag.  However, if I could build it myself that changed things!

For Christmas, I received a copy of Full Circle – A Treatise on Roller Locking and that really started the gears turning.  It is an excellent book with hundreds of original documents along with the history of development for the roller locked action.  Quite an interesting story if you’re interested in such things.  Don’t let the pricetag fool you either it is a limited printing and books like these tend to go up in value over time not down.

I did what I normally do next and start scouring the web for information.  Unfortunately, the general attitude of a large number of HK enthusiasts is if it didn’t come from Germany, it is probably shit.  If it has to come from the states, you’re not smart enough/skilled enough to do it yourself and should pay one of the licensed clone distributors or experienced builders to build you something.  Now these aren’t the Lego like AR-15 but they aren’t THAT complicated either.  The following is information I have found, reversed engineered from other deactivated roller locked guns, or just plain things that worked.  It may not be the best way, it definitely isn’t the only way but it is my way.

 

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For starters, let’s define a list of all the parts we need in order to have a functioning roller locked firearm

Receiver: For HK this is the sheetmetal portion that is folded and welded

Trigger Housing

Trigger Group:  Includes the ejector as well

Bolt Carrier: Holds the bolt head, firing pin, and locking piece

Bolt Head: Holds the rollers and extractor as well

Recoil Assembly:  Recoil spring and Rod

Barrel

Trunion

Cocking Tube

Cocking Tube Support

Cocking Handle

Stock/Rear Plate

Front Sight

Rear Sight