I bought a Model 99 Savage Brush Gun .358 from a friend about 7 years ago, and put together some loads at the time with AA2460 powder, and the SAECO # 352 250 gr. GC, and the Lyman 358009 280 gr. GC. I decided to get it out and shoot it, but the weather has been wretched here, snow, sleet, and rain and back again and about 33 degrees. So I shot off my back deck at twenty-five yards. I can see into the woods to where the bullets will strike, with the leaves gone, so no hunters back there. My friend's 300 yard range is not usable in bad weather. The result with the SAECO 250 gr., 36.0 gr. 2460 - keyholing! a fiveshot group of 3". Looking in my records, I had a group of 4 shots in 2 1/2 " at 100 yds, with one shot lost (I thought a bad bullet) but it was in August, 80 degrees.
So, cogitating about this, I fired a group with the 35809 280 gr., 34.0 gr. 2460 - five shots into 0.8 ". So not the weight too great for the twist. Wrapped the nose portion of the #352 with teflon tape as used for pipe threads to center the round in the throat - better, 5 in 2.3", 4 0f those in 1.3" but high & low shots show slight yawing.
Bore ride problem? the 358009 measures .350, length measures .36 forward of the foremost band. the #352 also measures .350, but only for .12 forward of the foremost band to the turn of the ogive. The bullet is apparently not starting strait into the throat. I'm thinking it is not a mould problem, but perhaps if I crimp the bullet one groove back so as to it further forward into the throat to start with. That is what I will try next.