I know this general subject has been addressed before:

https://www.milsurps.com/showthread.php?t=57996
https://www.milsurps.com/showthread.php?t=52657
https://www.milsurps.com/showthread.php?t=49858
https://www.milsurps.com/showthread.php?t=56696
Etc.

... however, for those of us who actually want to mount one on our Mk Vs, I finally figured out a way to get it done, and easily. Have done this on my own semi-auto Mk V and for a friend on his Mk II (his choice!).

This mod requires the following:
  • We used the foregrip from Sarco (in the US): (which is out of stock at Sarco as of this writing, but I've seen the same grip elsewhere). Note it has the thin-wall mounting tube rather than the very thick walls seen in one of the reference links above. I'm sure this is a repro, but the quality is excellent.
  • Two 4"x4" blocks of 2x4 pinewood, or equivalent.
  • A section of 1.5" ID galvanized fence pole (very common in the US; can't speak for the metric world). I bought a pole at my local Tractor Supply Co; also sold at Lowes & Home Depot, etc. I cut a 4" section out of the pole [A SQUARE CUT IS REQUIRED!] and filed the ends flat with no burrs.
  • Rubber mallet

The problem is the ID of the grip mounting tube is somewhat less than the (nominal) 1.5" OD of the Sten Nut Barrel. It's far too tight a fit to slide over the Nut Barrel, which makes sense because it's supposed to remain in position after mounting, and will uniformly be used to tighten the Nut Barrel against the main gun tube.

FWIW, here's my solution. I didn't take photos of the process, so the one below simply shows the galvanized tube in place after I'd already finished grip installation and also installed the foresight assembly:

  1. Typically you'd select a Nut Barrel that has the cooling/lightening holes only at the fore and aft ends (not in the middle). However, this mod will work with a typical "Mk II" Nut Barrel with three rings of holes too, although the grip strap will partially cover the center ring of holes.
  2. Thread the Nut Barrel fully tight on your gun and mark exact bottom dead center with a pencil or such. The BDC marks should be right at the sleeve/nut weld and also about 2/3 of the way from the back to the front. The upper mark ensures you align the strap when first placed, and the 2/3 point mark ensures you keep it aligned as you pound the grip ring down the Nut Barrel.
  3. Before mounting the sleeve, "dry fit" the wooden grip to the Nut Barrel and observe exactly where the sleeve must end up so the wooden grip is properly placed. It's easy to mount the sleeve too far forward or too far back (ask me how I know).
    [Start to mount the grip ring from the aft end of the Nut Barrel.
  4. Place the Nut Barrel open end down on a piece of fairly soft wood to protect the open end. You may find it easier to control by placing the open end on an anvil or other solid steel surface.
  5. Align the threaded hole in the sleeve with your mark at the Nut Barrel sleeve/barrel nut weld.
    [*
  6. Carefully place the 4" length of 1.5" ID galvanized fence pole on top of the grip sleeve, put a block of wood on top of the fence post section, and tap the grip sleeve down to the desired location.
  7. Start moving the grip sleeve into final position with gentle taps with the mallet. Ensure the center of the threaded grip mounting hole remains aligned with your pencil marks. Much stronger blows will be required once the grip sleeve starts moving, but DON'T use hard smacks to get the grip sleeve started onto the Nut Barrel (again, ask me how I know...).

Obviously Sten Nut Barrels are not particularly uniform in size, but luckily they are plentiful and cheap. You'll probably have to re-Parkerize or repaint the assembly after you're finished, but this is trivial.

Hope this is useful.
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