First, are the bullets you loaded cast or swaged? I ask only because some folks think that lead bullets are lead bullets. Cast bullets are usually harder than swaged and their loading characteristics can be different.
Second, preventing leading is not simply a matter of reducing the velocity of the load - it can be far more involved. (As a beginner the following may be more than you want to hear, but bear with me.) The most important factor is the fit of the bullet in your revolver. The bullet should be very close to the size of the cylinder throats, otherwise the powder gas will blow past the sides of the bullet and melt off droplets of lead - this is the primary cause of leading. Some revolvers will never shoot cast well because their dimensions are wrong - the throats can be smaller than the bore, guaranteeing leading. Veral Smith (see the LBT forum) was among the first to publicize this dirty little fact of life with cast bullets.
Next, your 6 grain load of Unique may not be the best choice....this depends on the hardness of the bullets you are loading. Alliant's web page shows 6.8 grains of Unique as maximum with a 158SWC at 1295 fps, so your load is close to max. If your bullet is very hard, then you will need a high pressure load to avoid leading - high pressures will expand the bullet and seal the bore against powder gas blow-by. Too-low pressures and hard bullets will cause leading.
Last, some leading will
always occur, just as some copper fouling will always occur with jacketed loads. A light wash of lead hurts nothing, but when visible lumps begin to show up you need to remove it and decide what about your load is the cause. One of the best ways to remove leading quickly is to buy a package of
ChoreBoy scouring pads at the local market - the copper variety, NOT the steel variety. Wrap a wad around a loose bore brush, wet with solvent and scrub the bore. This will remove the toughest leading quickly if you keep adding fresh, sharp pieces of pad, and will not damage the bore. I cringe at the use of steel wool in an accurate barrel.....
You may have no problems at all, time will tell. When you get things right you will love shooting cast. Let us know how your shooting goes.
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