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**Mike Irwin** · August 3, 2008, 12:14 PM

I posted a response from IMR regarding Trail Boss some months ago warning against using jacketed bullets.

I've also heard from several sources not related to IMR claiming significant pressure excursions while attempting to use jacketed bullets.

"If my aging memory serves, basic physics says pushing say a 300 grain bullet down a bore should not be different whether its lead or copper jacketed. The only difference is the coefficient of friction which should actually be less with a jacketed bullet."

Friction is higher with a jacketed bullet due to the jacket's hardness. Lead has a certain amount of natural lubricity associated with it, I guess is one way of putting it.

Then there's also the much greater amount of swaging force needed to push the jacketed bullet into the rifling in the first place.

I'm more than willing to take IMR's recommendation on this and use Trail Boss only with lead bullets.

After all, they're the guys with the ballistics laboratory set up that runs what, 50 million or more, the guys who test hundreds of thousands of rounds of ammunition a year, and when you think about it, the guys who have absolutely NO logical reason to shut off one of their products from a significant portion of the reloading community.

That would be like Ruger saying "Oh, we don't recomment that men over the age of 27 years purchase our revolvers."

August 3, 2008, 12:14 PM	#10
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	I posted a response from IMR regarding Trail Boss some months ago warning against using jacketed bullets. I've also heard from several sources not related to IMR claiming significant pressure excursions while attempting to use jacketed bullets. "If my aging memory serves, basic physics says pushing say a 300 grain bullet down a bore should not be different whether its lead or copper jacketed. The only difference is the coefficient of friction which should actually be less with a jacketed bullet." Friction is higher with a jacketed bullet due to the jacket's hardness. Lead has a certain amount of natural lubricity associated with it, I guess is one way of putting it. Then there's also the much greater amount of swaging force needed to push the jacketed bullet into the rifling in the first place. I'm more than willing to take IMR's recommendation on this and use Trail Boss only with lead bullets. After all, they're the guys with the ballistics laboratory set up that runs what, 50 million or more, the guys who test hundreds of thousands of rounds of ammunition a year, and when you think about it, the guys who have absolutely NO logical reason to shut off one of their products from a significant portion of the reloading community. That would be like Ruger saying "Oh, we don't recomment that men over the age of 27 years purchase our revolvers." __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.