The Jamaican duo of Dave and Ansil Collins had a brief fling with international fame when their single Double Barrel hit the charts in 1971.
This wasn't a brothers duo. Dave was Dave Barker, a session vocalist, while Ansil (or Ansel, as he was billed on the Double Barrel album) Collins was a keyboardist, usually playing a cheesy sounding organ.
The duo was shortlived. After an album based on the hit single, Barker and Collins went their separate ways.
You'll notice that the Double Barrel single above is labelled Version 2. This is an unadulterated instrumental, without Barker's shouted vocal interjections, and appeared only (as far as I know) on the flip side of the 45, which was issued on the Techniques label in Jamaica and the U.K. and on Big Tree in the U.S.
Double Barrel (Version 2)
This instrumental track did not appear on the Double Barrel LP which followed, although the album did include a track called Impossible Mission, a rejigged version of the title song.
Check out the difference in the album cover art between the U.K.-Jamaican release and the U.S. one.
Notice the naked women in the gun barrels. These were cut out of the U.S. release. Also "Ansel" is spelled with one "L" -- on the U.S. cover it has two "L's." On the single it was "Ansil" - "I" instead of "E" and with one "L."
There are a several options for obtaining Double Barrel and other tracks by Dave and Ansil Collins on either CD or as downloads. View them here. Many of the album tracks are instrumentals.
And finally here's the hit version of Double Barrel.