Leading problems - Taurus 24/7 Pro C DS in .45ACP

[Steve in KC]

ok, so I screwed up.

I'm a tester by trade and should've known better than to go with my initial measurement.

I replaced the battery in my calipers to ensure I had fresh juice. Cleaned them too, and zero'd out.

I then re-slugged from throat to muzzle and can now say that I was wrong.

I am slugging at .4515" The projectiles are also .4515" on average.

So I'm just a wee bit undersized, but not enough to cause gas cutting IMHO.

So, in short, I think these bullets are just too hard.

 

[918v]

.466"? Are you sure? Stick the small jaws of your dial caliper in the barrel to confirm.

 

[243winxb]

You could try tumble lubing your bullets with Lee Alox to see if lube is the problem. If you look at Lee's hardness chart to compare the hardness needed (BHN) to pressure. Max for 45acp is 21,000 PSI. You would need a BHN of 16.6 or more to keep from leading. If you believe Lee. Its possible that the alloy was not fluxed correctly also.

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[918v]

So, in short, I think these bullets are just too hard.

or the chamber throat is too large.

 

[rcmodel]

Or the bore is rough with microscopic burs from the rifling and needs lapping to make it slick & smooth. (See post #2)

rc

 

[918v]

Does Taurus have hammerforged barrels? Sig does and they lead too. In my experience, broach-cut barrels that have tool marks running in the direction of bullet travel do not lead. If you look at a hammerforged barrel through a borescope, you'll see tool marks running against the direction of bullet travel and those barrels tend to lead, unless you lap the hell out of them.

 

[243winxb]

Just finished my 200 round test with hard oven heat treated bullets. Accuracy is normal @25 yds with S&W 645 9 of 10 shots went into 2 7/8" One flyer inlarged the group to 4 13/16". These were rounds 191 to 200. Yes, the barrel does show more fouling compared to softer air cooled bullets. Accuracy is not affected.