Peter,
I'll drink to your proposal but it might take me a little while to get to your favorite pub.
Vincent,
That link to 1919a4 was great. I read about the HA Bren in Small Arms Review. Everything was wonderful. Wiselite and head-spacing OMG. When I first decided to build semi Bren I found a tutorial by "Pirate", another so-called professional builder. At that time the IO cut receivers were available so that there was one cut to weld between the locking shoulder and the barrel socket. He, probably like Wiselite, set up the weld by fitting the magazine, not setting the headspace. I couldn't believe it. I set the headspace first then checked the mag fit. If the mag didn't fit then there was something very wrong.
Wally G.
Thanks for your details of the HA build. I had read about what Len had to go through to meet ATF specs. The latest ATF approval letters are far less restrictive.
Gary,
Yes my Brens run better on .303, but they also run without any problems on 54R. If you are building your own and are willing to take care of all the small details they can be made to work with 54R both semi and FA (see post from C310 pilot about FA 54R Bren). The details being headspace, timing and the magazine. The ZB39 mag was not made for the 54R round and although it can be made to feed that doesn't mean it will work properly without modifications. There are no other reasonable magazine options.
For most people what I stated above is not the case.
My 2 cents
Djandj,
It's impossible to tell how the wood plug affects mag capacity and feeding. As far as I know this issue has never come up. I guess there are not many people with Brens in California.
Joe