Ive been pouring jigs and weights in a bismuth alloy for about 2 years now. Certainly more costly then lead but a whole lot less costly than tungsten.
I'm melting and pouring at about *500. You won't be twisting sprues off these items. You'll need gate shears to trim, and sandpaper or file to clean where you cut the sprue off.
As far as powder coating, I'll powdercoat the next day or even longer after I pour to allow the items to cool completely. The I heat them gently over an alcohol lamp and dip them. Plan on ruining a bunch due to heating to a too high temp.
I hang them once again to cool. And then finally heat them in an oven set at 275 for smaller stuff, and 290 for the bigger stuff. Jigs weights or whatever are hung in oven as it heats to temp, and once the set temp is reached I shut the oven off.
Not as perfect a finish as a lead jig, but not too bad. Instead of powder coating you can also spray paint them. If I spray them, I but a finish coat of clear.
Alloy I use is around $15 a pound. There is a learning curve to pouring the alloy as it behaves differently than lead. It expands as it cools, so at times it can be a botch to remove from the mold. No actually their always that way. Especially when pouring bullet type worm weights. For jigs I graphite coat the mold, and after pouring I give the mold a whack with a small hammer.
Bullet weights are the worst! The pull pins are a royal pain to remove. I've tried using WD 40, Pam, and I'll be pouring this weekend, and I'm going to experimant with Never Seize.
The items aren't as fragile as you might be led to believe. But are more fragile than lead. The way I test for lead vs alloy when I get sloppy on the work bench, I whack'em with a hammer. If it shatters- alloy. If it flattens- lead.
As far as weight. Iypically pour 1/4, 5/16, 3/8, and 1/2oz items. Using the same molds as one would use for lead. Weight difference is negligible.
Example... a 3/8oz jig should weigh .375 oz, where as an alloy jig will go roughly .355 to as close to.370oz. Density of course is different, so if you want a faster fall, just move up to the next 1/16 or 1/8 oz.