Powder choice and leading?

[Old Ephraim]

Howdy all,


Some of you fellows were real helpful with some questions I've had in the past, so I though I'd come back for some more.

I have a 625-6 (45 ACP) that I've been playing with for about a year. (and wow!!, is there anything not to love about this revolver??)

I've been working on some target loads for the past month, and I've noticed that the chambers and barrel only lead under certain bullet/powder combinations. I'll try be clear in explaining this...

Using Oregon Trail 220 SWC, .452 bullets and 4.8 grains of Titegroup I get almost no leading. (I couldn't find info on the Brinell hardness of these, but I'm guessing there pretty durn hard) Same bullet with 5.5 of Unique...no leading.

I recently bought some Missouri Bullet Company 220 SWC, .452 bullets, advertised as 'Target', with a Brinell hardness listed on the box as '12'. With this bullet over 5.0 Unique, no leading. Same is true with 6.0 of Unique. But, when I load this bullet with the same 4.8 of Titegroup that worked so well with the Oregon Trail bullet, the barrel and chambers are a mess with lead.

Accuracy wasn't an issue with any of the loads mentioned, they all shot great. My question (finally!!), is...Is the leading caused by using a softer bullet with a faster burning powder? I noticed that Titegroup lands 12th on the burn rate chart, and Unique comes in at 23rd.

I'll wind up sticking with the MBC bullet and 5.0 of Unique, but if there's something to be learned here about lead hardness, powder burn rates and leading my pistolas, I sure would like to know.

[MtGun44]

Have you measured the actual (not box claim) boolit diameters? Typically, undersized
and too hard boolits, esp with the commercial hard lubes which are only moderately
decent lubes at best in my experience, are most likely to lead, not the most commonly
claimed 'too soft' boolit alloy.

At this point, not enough info to figure the prob, but it is not likely the particular
powder or too soft a boolit, these are rarely the root cause of leading. Leading
is usually a boolit fit and lube quality problem, with too hard being more often
a problem than too soft.

What are your throat diameters and the groove diam of the barrel?

Many S&W .45 ACP revolvers have way oversized throats, and this can be
the whole cause of throat leading with hot powders like Titegroup with the hot
gases blowing past the undersized boolit and melting the sides.

Read the sticky on revolver accy and then measure your throats and
groove diam (slugging or with gage pins for the throats) and report back, it will
be easier to figure out what is happening.

Bill

[Lloyd Smale]

yup faster burning powders can cause more leading. Using ball powders can increase leading in a gun that leads easily too. Fix the cause of the leading and you can run about any powder.

[Shuz]

A few of my .44 mag. revolvers have cylinder throats that are a thou or two SMALLER than the bbl. These revolvers tend to lead slightly with mid power, 950 to 1050 fps loads when using Green Dot, Unique or NM-04. However, when I stoke the cases with either WC820 or 2400 to achieve the same or slightly higher velocities, the leading is greatly minimized or is non-existant! I realize I could enlargen the throat diameters to be commensurate with the bbl diameter, but it just isn't worth the time. If I believe a certain revolver is starting to lead a little more than I like, I simply fire 5 gas checked boolits stoked by 18g of 2400 or WC820 and the bbls come out slick and clean.