Interesting thread Buffdog. Could they have been built for some type of testing as Peter stated thouigh. I have a No.4, sn. EX2 in caliber 7.62 as done at Enfield. Skennertonicon thinks it's one of several built to test barrel twists for the L7 GPMG. It's a lovely rifle and has a .303 magazine cleverly modified internally to feed 7.62 rounds.

Charlie is right about the PH 5C and AJP 4/47. They don't foul the forend and I stand corrected. EX11 is definitely shaved for a Central or possibly the PH 5A configured for the No.4. I have one here and got it out to look. I've never installed it for that very reason.