The rifle you refer to was a 1,000 yard HG. By the rules, they have to ride in two-piece rests, and the rests have to be sandbags (but both can be on a pedestal). The tube was 3" schedule 40 stainless pipe -- that's about 3.5 inches o.d. I have the material to build a new one, using 3.5 aluminum (6061 T-6). Joel has used his HG -- a picture of it also on 6mmBR.com -- to win a whole lot more than his share of matches with a similar tube. He has moved to a 5-in tube, using 6061 T-6 aluminum, and that gun is now shooting as well as the first. Jeff Rogers has set all kinds of Australian records with tensioned-barrels.
I have made several 1K light guns using tensioning tubes. Most have shot well (read: won); some have not.
I have made a PPC Sporter weight rifle with a tensioning tube. The first attempt was a disaster, it had water/antifreeze inside, but the barrel was so close to the tube that changes in heat during the first 10 shots made it string. When I re-did the tube & took the water out, it settled down.
In a way, the tensioned barreled rifles are like tuners. They show a lot of promise; I think they work better (more consistent) than tuners. But we don't know how to guarantee success yet -- no "cookbook formula." There are far fewer people using them than tuners, so information comes slowly.
People looking for a new, technical edge to success are usually out of luck. A lot more things fail than succeed. That there has been as much success with tensioned barreled rifles as we have seen does show something is there worth chasing. But we're not to the point where it is a quick fix; results are still as you would expect with experiments, some good, some bad.
If you want to join in the fun with a Sporter-weight PPC, I'd say find the best 6061 T-6 tubing you an get, probably 1.375 o.d. with .125 or less wall (.080 will work with a 1.25 barrel), a No. 5 taper barrel (that's a Shilen taper, whatever is similar from any maker would be fine), & have at it. If your forearm channel is not 1.5 inches (few are), reduce the o.d. of the tube proportionately. Simplest is to just butt the tube against the action. Watch out for marring the action if it it too is aluminum. Make a nut for the barrel so as to put tension on the tube -- I like a full 1-inch long nut. With aluminum tubing, you don't need too much tension. You'll distort the tube if you over-tighten it. Face off the tube as accuarately as you would a barrel, BTW, and the nut should have a shoulder & well-fit tenon.
Far as that goes, you could probably try the tensioning with three rods, a couple of plates, & the nut. Would solve the problem of getting even-walled tubing.
But in any event, you'll be off on an experiment, and if all you want is quick wins, there are likely better ways to get them.
