Awful leading was always something that happened to other people...until now.
My recently-purchased New Century (TL) has a bore that runs from about .4315" in front of the forcing cone down to .431" at the muzzle and throats of .432". Timing looks to be extremely close, I cut a brass rod at a slip-fit for land diameter and felt no hitting or binding on the throats when locked-up, even when pressing the cylinder against it's stops.
It leads like crazy using the .430" bullets I bought before measuring throats and bores.
Yes, I *could* buy some molds and fool about with casting projectiles, but I have enough trouble finding time to go to the range and reload as it is, so I'd just as soon throw a little money at it and move on with my life.
It's a target-sighted gun, so bullet weight isn't a critical factor. In a perfect world I think I'd like to find a Keith-style SWC in the 200-220 grain weight, but really I'll take anything that fits and groups.

Only ones sized .432 that IMHO are quality cast with good alloy & good lube are : Matt's Bullets has a 250gr RN LY 429251 for $22/100 , 500 /$ 105 . Montana Bullet Works hand casts & are more expensive but quality is first class has an LBT design Ogival Wadcutter Plain Base 240gr $34.85/100 , $174 / 500 & 255gr Keith SWC for $36.40 / 100 , $182 / 500 .
FWIW I've bought from both & been more than happy . Both offer a quality product for a fair price . Before I buy a mold I'll buy from these guys & if it works out then I'll buy a mold .

I have been very happy with the product from Matt's Bullets as well.

Beartooth Bullets offer .44 cal bullets up to .432". Beartooth Bullets Secure Online Shopping

Just the ticket for Marlin 44mag microgroove leverguns .

+1 for Montana. Also, be sure to get the correct BHN (bullet hardness) for the load used. You can also find that on the Montana site.

Dang, that's well into JHP bullet price. My own fault for buying an expensive gun I guess. I'll place a few orders and see how it works out for me. Considering I usually like to ladder several different powders for any given bullet, it's not hard to burn a few hundred fully working up a load. Luckily my LPP situation isn't too dire yet or I'd really be crying about component costs!

I'm finding it frustrating that there are so many casting houses but none of them manage to be a one-stop shop for me. Even before I was looking for these .432" slugs, it seemed to take a few different outfits to cover my needs. Well, it's that or cast I guess. I can't even imagine how non-reloaders manage! Just buy boring guns I guess.

I'm sure there are some good cast bullets available commercially, but searching to find the best for your purpose may be a chore, especially now. You may prefer not to cast your own, but casting gives a flexibility in bullet selection unavailable elsewhere.

The drawback is learning the process. It does take time, but well worth the effort if you're interested in the best in handgun accuracy and prefer not to have to settle for a bullet that's a lesser product or a good product that's not exactly what you want.

Penn Bullets will size to whatever you need.

Granted, between alloy mix and diameter, diameter is often the more critical of the two, but the alloy mix remains important for best results. If they'll also provide a choice of alloy mix or at least something that's not too hard, then that would be a good place to start if you're going to stick with a commercial source.

I don't know anything about Penn bullets, but there are always exceptions and a sample of what they have available would certainly be worth trying.

How much do you care about that gun???

I realize you don't cast or powder coat, but an easy way to add girth to a boolit is to PC it, and carefully lift the bullet out of the powder instead of shaking off the excess. This method easily adds several thousandths to a bullet.
You have a gun. It needs bullets. You could buy some lead bullets and soak off the lube, then PC them yourself. Or maybe they would sell you some without lube on them.
Powder coating is a very simple operation. Go over to CastBoolits.com. They will get you everything you need.

Or you could sell it and get something else. Or you could turn it into a safe queen.
Your choice.

I've used him before, he's local to me. It's a small operation at his home. I think he has 2 standard alloys to choose from.

if you have a lathe, you can make a lead bullet sizer, any size.

I know you can buy unsized, unlubed from Missouri Bullet Company. Then tumble lube them yourself. That is going to be the cheapest route. They do offer a 240gr SWC as well as other weights and profiles.

If you can find a quality shop with...........
sample packs, it will cut your time down in finding what your weapon likes.

Most have Grs & Dia. as an option.

Good shopping.

Not in stock at the moment but Roze sells a .431 JSP. Worth a try .

I think he's gone exclusively to coated bullets at this time. How that effects leading I don't know.
I've bought 432 44's from him for my lever gun.

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To cannon, all men are equal

I'd suggest measuring the cylinder throats for two reasons; first to make sure they are all larger in diameter than the groove diameter of the barrel, and second to give you the best diameter for your cast bullets. For my 7 revolvers I size all cast bullets to the same diameter as the cylinder throat diameter (bullet diameter is waaaaaaay more important than BHN!)...

All throats are a nice but slightly firm sliding fit on a .432"- gauge pin, hence the desire for .432" bullets.

Well, it's hard to find a nice clean New Century so while I'm open to find another specimen, I can't afford to get too excited about replacement. I'm trying to avoid safe queens and it's not the end of the world if I do wind up paying close to $.40 per.

Bear Creek offers an "oversized" 205 gr rnfp powder coated bullet for older .44 guns, check out the website but you'll have to call in your order--no online ordering at this time.

I use Steve's bullets almost exclusively in .38, .44 and .45 and I've been very pleased with the accuracy and cost of BC bullets.

If you shoot anything but sedate lead loads out of a Triple Lock you're nuts . That older barrel is soft & you can enjoy it the rest of your life & then some with mild cast loads . Matt's also casts a bunch of different bullets but does size most to .429 , worth a phone call to see what he has that'll drop @ .432 or more . Mild loads unsized as cast & tumble lubed with White Label 45-45-10 . 44 special with wadcutters.........old gal might take the 10 ring out .

Try GT Bullets. They have .432.

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S&WCA 1729

Montana...

I use Brazos TEK coated for all of my stuff. I was having leading problem and got some bigger bullets from them and he suggested I use a slower powder. I went to Unique with a larger bullet and they shoot very clean now. They also have the best price too. They might even be able to go larger if you talk to them. They offer 431 as an option and show bullets in stock.

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Ron
Southern IL

I try to match cast bullet diameter to cylinder throats as well. It is the single most important thing for good accuracy and minimal leading. Many cast bullet makers supply hard cast +-20 BHN bullets which isn't needed for low pressure loads.
To determine the proper bullet hardness for a given load, simply divide the chamber pressure (usually given in most reloading manuals) by 1400. So as an example lets say a particular load has a chamber pressure of 17,000psi. Simply divide 17,000 by 1400 to get the optimum BHN. In this example, a BHN of 12 is optimum for that load. If the bullet is too hard, it will not seal the bore and cause leading.
Matching the bullet to the throat diameter is a big part of the equation. However you will still have a leading problem if the bullet hardness is not somewhat matched to the load.