Leading at forcing cone with large throats.

[justindad]

My Uberti .45 SAA Regulator (4.75” barrel) will sometimes leave lead stuck to the forcing cone - not just in the forcing cone but also on the face of the forcing cone. I have to chip the lead off with a nylon pick, even after letting Hoppes #9 sit on it for two days.
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I slugged the muzzle of the barrel, and measured a bore diameter between 0.4496” and 0.4507”, depending on which grooves I was measuring. The cylinder throats have a snug fit with a bullet measuring 0.4527” and a 0.4550” bullet does not fit.
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I shot about 100 rounds of 255 grain SWC with a modified Felix lube, moving between 750-800fps. The alloy was a 50/50 mix of COWW and SOWW, and fluxed with Root Kill to get about 0.2% Cu in there just for kicks. Powder was Ramshot True Blue. My sizing plug measures at 0.4496”.
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I do not get barrel leading with 96-2-2 alloy or harder, but I need at least 94-4-2 in order to keep my forcing cone clean after 50 rounds going 775fps. This 50/50 alloy is the only stuff that put lead in the barrel. Based on what I’ve read, I thought my 50/50 alloy would be fine, but I guess not.
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My biggest surprise is the 0.0011” roundness error in my barrel. Accuracy with this pistol is better than me, and sometimes I get 3 out of 5 holes touching each other at 15 yards.

[Messy bear]

Not sure if that out of roundness will hurt things but the soft alloy should be plenty adequate with mild loads. I would try some different components such as powder primer ect. True blue is undeterred and sometimes causes leading.
Hope ya get it

[725]

Of course, without your revolver in hand, there are a few areas I'd examine: Does it time up properly? Charge hole (cylinder / chamber) sit properly in front of the barrel. Gap between the cylinder and barrel correct? Forcing cone machined well & smooth? I re-cut my forcing cones with a hand tool from Brownell's (easy as pie) that gave a different angle and it did wonders for me. Good luck.

[justindad]

My forcing cone looks like a cheese grater. I’ve been looking out for an 11 degree chamfering kit on Brownells for a few years now. Every time I look I haven’t been able to get all the parts.

[DougGuy]

My Uberti (avatar) has a .451" groove and .4565" throats. I use 454190 cast in 50/50+2% and SPG or other soft lube, and size to .456" never have to clean the barrel, no leading that I have observed. I think I am loading 9,0gr Herco pretty much a standard pressure load. I did recut the forcing cone to 11° right off the bat as it was rather iffy.

[justindad]

Looks like I need to load some as-cast boolits into fired brass that wasn’t sized when the primer was removed.

[Outpost75]

Looks like I need to load some as-cast boolits into fired brass that wasn’t sized when the primer was removed.

That is exactly what I do. Redding Profile Crimp is final step. I load 6.5 grains of Bullseye with Accurate 45-264H. Lube is 60 beeswax to 40 olive oil. Bullet alloy is 1 to 30 tin-lead.

[mdi]

I don't care for "snug", "fall through", "push through" regarding cylinder throat measurements. I slug or use pin/plug gauges for accurate throat measurements. On all my revolvers I size my bullets to the same diameter as the throats regardless of BHN. I have eliminated nearly all of my revolver barrel leading. You mentioned "I slugged the muzzle of the barrel," and I would hope that you meant you slugged the whole barrel from the muzzle end and not just the barrel muzzle...

IIRC; and I'm old and it's been a couple decades, I experienced forcing cone, frame, and top strap leading from bullets larger than throats (more like lead spray from lead being swaged going through a tight throat?)...

[DougGuy]

I size my bullets to the same diameter as the throats regardless of BHN.

You've never loaded ammo and after it sits for a few months the antimony in the mix has caused the boolits to grow just a tad, but enough that they won't chamber? You NEED a little wiggle room in the throats .0005" works great,

The bigger the boolit, the more growth will happen as they sit and age harden, whether loaded in cases or not unless they are really soft alloy.

[justindad]

That is exactly what I do. Redding Profile Crimp is final step. I load 6.5 grains of Bullseye with Accurate 45-264H. Lube is 60 beeswax to 40 olive oil. Bullet alloy is 1 to 30 tin-lead.

Makes me wonder… for revolvers, should sizing only be done when needed for proper chambering? I imagine a slow powder that needs a tight crimp (e.g. H110 in .357 Mag) should be poured into a case that has been sized for maximum neck tension. I’m going to explore that.

[mdi]

You've never loaded ammo and after it sits for a few months the antimony in the mix has caused the boolits to grow just a tad, but enough that they won't chamber? You NEED a little wiggle room in the throats .0005" works great,

The bigger the boolit, the more growth will happen as they sit and age harden, whether loaded in cases or not unless they are really soft alloy.

Nope. Never experienced any problems from old cast bullets growing. I Normally don't process my cast to the point of being seated in the next step, can be from a few days, to a couple years. I often will cast a bunch and store them away waiting to be lubed, or PCed, sized and loaded. More often than not, sizing is just prior to seating. I have never needed five ten thousandths of an inch "wiggle room" (.0005". Ambient temperature can probably vary the diameter more than that). I have never needed to cast some bullets then measure the diameter, charting the change over a specific period of time and in my casting "career", never needed to even just for personal info.

[LabGuy]

I don’t know if they “grew” or changed hardness. I once took a 20 year sabbatical from shooting. Loads that were leading the barrel were not 20 years later. Same gun with 20+ year old reloads.