I have a YHM R9 with a 3 lug adapter coming for my MP5 clones (Zenith MKE full size, and Zenith USA K model). I've been told I may need to swap out the locking mechanism, particularly on the K model.
Looking for advice from anyone who has been in this situation.
Will I probably have to swap some parts?  Will I be able to make them run with and without the can?
Should be getting it sometime this week, so I want to gather info ahead of time.

Thanks.

In my experience, the K is more sensitive to the locking piece used.

Is there a "middle of the road" where it will run with and without? Or is it pretty much dedicated to the can after changing the locking mech?

You don't need a new locking block for the full sized guns

I added the RCM 80* locking piece to my PTR 9 KT.
Had to change rollers to get the bolt gap back into spec.

It ran the same ammo just fine with or without the suppressor after the swap.

Supposedly the 80* locking piece slows down rearward movement so you don’t get roller dents in the upper.

HK recommends the locking piece upgrade if you are going to shoot full auto in a K gun with a stock.
Since I was using a brace and running a binary trigger, I added the RCM part as cheap insurance.

If you are not running NATO spec ammo in full auto, you will probably be fine.

I’m in the “better to have and not need camp”.