I ran the numbers thru the barrel wear spreadsheet (barrellife.xls) and for use with Varget the 6mmBR was calculated to be good for 2000 rounds and the 22BR at 1800 rounds. They look to be pretty close with each other as far as wear goes but real world data would be better than the calculations!
Ian,
I agree with your last sentence. I find it difficult to believe that .22BR will be so close to the 6mm version. That's a fair bit smaller bore size to be shoving 30gn's worth of hot gas from a load of Varget, Re15 or H4350 down.
Anyway, we're back to how you define 'barrel life'. Kevin Thomas formerly of Sierra, quotes 6BR barrel life figure from his work with that company in a post on 'Barrel Life' dated April 2009:
I'd call it 1200-1500 rounds at best, based on the 1/2 MOA figure mentioned earlier. That's about the point that I expected to see accuracy drop off with SMK 107s from our test barrels, and I was actually running loads a bit slower than those cited here. The problem here isn't so much one of capacity or speed, but bullet weight; heavier bullets wash out throats faster than do the lighter bullets at higher velocities.
That rather shocked me at the time, but as a long-time benchrest shooting friend put it, few 6PPC barrels hold BR accuracy much beyond 1,300 rounds, and the PPC case capacity and charges are smaller than the BR's. (Also, 6PPC is all 65-68gn bullets in competition, while 6BR is often running 40gn heavier at that end. As Kevin T says, heavy bullets are barrel killers thanks to the extended period that high pressure and temperature gasses afflict the throat area due to a heavy bullet's greater inertia.)
I've just got my .223R F/TR rifle up and running with 90s, and I doubt if I'll get much over 2,000 rounds of F-Class grade accuracy out of this combination. We'll see - I hope it's more, but have my doubts. 4,000 rounds of mixed 69s, 73s, 75s and 80s (mostly the heaviest weight) in a previous .223 saw 110 thou' erosion of the leade in a Lilja barrel, despite modest loads - 2,700-2,750 fps with 80s, 2.950-3,000 fps with 69s.
Laurie,
York, England