huldra 5.45x39

[Blue Avenger]

picked up a huldra mark IV (adam arms) 5.45x39 piston upper long ago. Today I was looking at changing the barrel to a .223 variant. Gas/piston block is pined on and pins did not move. was tapping on the left side. did not try right. also noticed that there are threaded holes on bottom of block and marks on barrel from screws. that got me wondering if there had to be some preload needed to remove the pins or it was just used to hold during assembly.

[Blue Avenger]

It's apart now. Now do i drill new pin holes in a new barrel or dimple it. would like to recycle the piston system.

[Dave Hoback]

The Threaded holes on the bottom of the block are there for set screws to hold the block in place while drilling new taper pin holes in the barrel. Do the same. Don’t need to dimple the barrel. The set screws should hold fine to drill new taper pin holes. Check your pins. They should be Taper pins. Hard to tell with the naked eye. Use a caliper to measure for major/minor diameter.