In yet another valient effort to get plain base bullets to shoot well in my 4" S&W M29 with the 0.4336" throats, today I tried using Rooster HVR lube, instead of the homemade lube EL#3 that was used in the previous experiment. Rooster HVR has been the cleanest lube tested to date in other cartridges.
All other components were the same as before, 250 gr. HTWW, deep seated plain base design, case necks turned to allow chambering the 0.434" bullets, 24 gr. H110, CCI 350 magnum primer.
After 5 shots, the barrel looked clean.
After 10 shots, I could see a few specks of fouling on one side of the barrel.
After 15 shots, one side of the barrel had a light but distinct coating of lead, while the other side of the barrel was perfectly clean.
The fouling wasn't that bad, and I would be willing to accept it if it were stable, but it seemed to be building up as more shots were fired.
Velocity was 1278 fps, 28 std dev, average group at 50 yards 4.8", all 15 shots in 6", the majority of them in a ragged hole. I am probably the limiting factor for accuracy because I haven't practiced with this gun for many years and it is not easy to shoot.
That compares to 1292 fps and 4.6" with my experimental lube EL#3, so Rooster didn't make any difference.
The sensible thing to do here is admit defeat and go back to shooting gas checks, but that would be too easy.