What parts are needed to be added/removed/changed to use a registered HK sear, currently set up in a pack for a 308 host, in a 9mm host gun?

Ejector? Hammer spring? Anything else?

Trigger housing

9mm ejector and 9mm hammer spring. That's it.

Thanks!

You'll probably want to use a hammer with the strut pinned to it (to avoid the strut bouncing off rarely).

Pinned struts are not normally found on 308 hammers, but the pinned strut can be used with all calibers.

It's also possible to shorten and stretch a 308 hammer spring where it's reliable with both calibers, although this requires some experimentation.

I used a pinned strut, rifle spring, a retimed hammer, so that the only change I made was the ejector. I each host had a empty trigger housing with the appropriate ejector in a ziplock bag.  When changing from 9mm to 308, remove the trigger pack, remove the 9mm ejector, place the 9mm ejector in a ziplock bag and put it in the empty trigger housing and put the 9mm host back together.

Open up the 308, take the ziplock bag out of the empty trigger housing, remove ejector and place it in the FA trigger pack, put 308 back together, done.

Worked on 9mm, 308, 762, 556 with just the ejector swap.

Attached File

I agree.  I regularly swap between a MM 23E, a PTR 32 shorty and an MP5 the same way.  I keep the timed hammer and rifle spring in place and just swap out the ejectors.  They all work fine and I suspect the rifle hammer spring helps slow down the cyclic rate on the MP5, although I haven't actually timed it.