Leading-free load process- Where now?

[longfellow]

Well, I've taken the advice of folks here and from Cast Loading manuals and I think I've come as close to a lead-free load as possible, with this particular bullet style.
I say this because I am shooting about as close to an ideal load for one who desires a clean barrel. In summary I will try to answer the basics about the gun/load and then I am asking of I am left with nothing remaining if I am to get closer to a completely leading-free load, other than a different bullet/lube.

***Gun- New Blackhawk Flat top 44 Special
***Dimensions - Groove - .4294, throats are all consistently .4315-.4318
*** Bullet - Accurate (www.accuratemolds.com) #430-220. This is a design created specifically for me. Sized .432 in a hand honed Lee push through die before lubrication.
***Alloy - Lyman #2 recipe.
*** Lube - Lee LA tumble lube once after sizing(I've tried twice with no appreciable improvement).
*** Load - Unique 6.5 grains (moderate), bullet seated without crimping so that the front driving band is fully inthe throat. For this I neet to apply a fair amount of force to get th cartridge in the cylinder as I am overcomming about a .0005 interference (which is universally recommended here and by all serious cast shooters).

Results - slight leading at forcing cone and very small amount on a few lands but only sporadically and only about 1/8 inch down barrel. This is after ten rounds.
Request - Is this as good as I can expect? Would a different design or a traditionally lubricated bullet improve things (I have heard of much heavier loads being completely free of leading.) Would a gas checked design basically solve the leading? or a style with more lube-holding capacity?

I can help a little by listing other variables that I've altered with no better results;
***Slower Powder - tried 13 gr of 2400 - no better
*** seating bullets just shy of throat restriction - worse
*** softer alloy (To test the "obturation" theory) - tried soft lead as well as soft lead with even higher load of Unique (7.5 gr) - worse.
***even larger sized diameter - tried .433's with both alloys- worse.
***smaller diameter - tried .430's with both alloys - worse. NOTE: I can go all the way down to 4.9 grains and this is so light that many combinations leave the barrel fairly lead free but I'd like a more 'universally applicable' medium load of about 800 - 900 f/s.

Thanks all. Feel free to ask any questions not answered here. I am about ready to place a bulk order of jacketed bullets and hope that I've missed something important.
Ed

[Unclenick]

Some more odds and ends:

First, it sounds like you are getting quite normal results. Firelapping the bore smoother will help further if you have any trace of a bore constriction. But even my very smooth .45 ACP barrels usually pick up very small patches and streaks like you're describing (if I have that picture correctly in my head). The thing is, I can (and have) put several thousand rounds through it without cleaning, and the streaks never got worse. It's like the lead wipes off as fast as it deposits, so the system is in equilibrium. You can test to see if you have that situation by putting a couple hundred rounds through without cleaning, then see if it's getting worse.

Load: QuickLOAD puts you at just under 10,000 psi. Still pretty light. I don't think there's anything to be gained by fussing with the load level or bullet hardness further. You could try placing a tuft of polyester over the charge (knock it down and work back up to the same velocity if you try this). It may add enough of a small barrier between the hot gases and the bullet base to help a little.

In the same vein, you can try a card wad stuck to the bullet lube on the bullet base.

For more serious base protection, try poly-wads. NECO sells some (scroll down on this page) for a nickel apiece, which is fine for a trial, but you can get a die and cut them out of HDPE sheet for less than half a cent. Merrill Martin always reported zero leading by this method.

(Note: P-wads and card wads usually separate from the bullet on firing and can hit your chronograph, so hang some stiff cardboard on it with a hole in the middle to shoot through.

Try sizing .4310"-4315" just to cover the bases. Half a thousandth under to half a thousandth over is the range I am most familiar with seeing success with.

Try getting some motor mica powder and sprinkling it on the lube when it's tacky but not yet fully dried, and roll them around a bit. This adds dry lube to the surface that is completely heat resistant.

Try adding a bore lube. Sprinco Plate+ Silver and a rubber stopper. A three day soak will give a semi-permanent lube. Makes the gun act as if the bullets were moly plated. It lasts about 1000 rounds in a rifle if you don't replenish it. It should make it a little more difficult for the lead to stick to the bore surface. If, for some reason, you don't like it, just wait until you've shot some more and it will be gone.

[bigwrench]

Today I was checkeing some .40 loads using two differant powders. I was actually trying to see for my self what was the big deal about shooting cast in polyagonal barrels. Using 3.8, 4.2, 4.6, 5.0, and 5.3 grains of Universal under 175 grn. tc cast from WW. Loaded up 10 rounds of each powder weight. And wanted to check each load in two differant pistols, IWI baby eagle, and Taurus 840. Also had loaded 10 rounds each using 2.1, 2.8, 3.4, 4.1, and 4.8 grains Tightgroup. After just five rounds of the loads using Universal I began to get minor leading with the lightest loads in the Baby Eagle. And as the heavier loads where fired, leading began to increase. Thinking to myself that cast bullets realy would not work in the polyagonal barrel, I switched to the Taurus, but the result was the same. After only five shots with the lightest loads there was already noticable leading.
At this point I was thinking that my lube was not cutting it and that I was headed back to the drawing board. I decided to go ahead and shoot up what I had loaded rather than pull them all down, and began shooting the rounds loaded with tightgroup. Right away I noticed that my groups had tightened up, and upon checking barrel, was suprized to find that no leading. Shot all the tightgroup loads with Taurus and had zero leading, and only minor leading in the Baby Eagle with only the 4.8 grain tightgroup load.

[bigwrench]

Maybe I should have started a new thread to post these findings, but It seemed to be relivant to your post.

[PawPaw]

bullet seated without crimping so that the front driving band is fully inthe throat.

I've never heard anyone say to NOT crimp cast bullets in a revolver. I've had bullets move under the recoil impulse and tie up the cylinder. I like a good crimp on revolver loads.

Would a different design or a traditionally lubricated bullet improve things

No, at that velocity, one coat of LLA is all that's necessary. I don't use two coats unless I'm pushing a bullet over 1300 fps, and at that point, that's when I install a gas check.

What do the throats look like on that revolver? They should be lapped to 0.001 over your forcing cone diameter. Have you slugged your bore? Have you checked for a restriction at the barrel/frame junction? Sometimes, on some Blackhawks, there is a small restriction under the barrel threads, where it's screwed into the frame.

My go-to .44 Special load is a good 240 grain cast bullet, a standard primer, and 7.5 grains of Unique. I'm not sure if I'm getting leading because I don't clean that revolver that often. Accuracy is just fine. It sounds to me like you're on the right track.

[Unclenick]

Bigwrench,

Your topic is almost a new thread, but still relevant to the Blackhawk because it points out that bumping a bullet up enough is necessary to stop gas bypass that promotes leading. (Especially if your are trying to force the shape into the corners of a polygonal barrel.) Too little pressure at the beginning can cause as much trouble as too much in some instances. The slower burning Universal just wasn't creating enough early pressure for you. Also, the faster powder's peak pressure drop due to expansion is faster than for a slow powder after the bullet gets moving. Expansion in your .40 at your bullet weight could be over 2:1 just by the time the bullet base gets to the case mouth.

I bet you'll get the same result with Clays or Vihtavuori N310.