actual bore size if .38 cal vs 9mm bullets ?

preventec47 · January 6, 2010, 08:13 AM

years ago my friend cast his bullets for 38 cal and 9mm out
of the same mold. I always thusly thought they were
the same size ( his of course were )
But recently I find that 9mm bullets are .355 and .38 are
.357 caliber. There is two thousandths difference.

My reason for asking is I want to shoot a 90gr speer "9mm"
(.355) bullet in a 38 or 357 magnum.

I wouldnt think that just 2 thousandths would cause
the bullet to rattle down the barrel but i could possibly
see lower pressures being generated because of
a lesser tight fit etc. Anyone ever used .355 jacketed
bullets in 38 or 357 pistols ?

SL1 · January 6, 2010, 08:38 AM

A couple of things:

First, cast lead bullets are typically made about 0.001" larger in diameter than the jacketed versions for a particular caliber. So, 9mm cast are typically 0.356" and 38s are typically 0.358". Cast bullets are often run through a "sizer" to make them a particular diameter (and improve their roundness, in some cases). It would be easy to use the same mold to cast bullets around .0.358 or larger and size some to 0.356" for the 9mm. however, sizing bullets more than about 0.002" can adversely affect accuracy. It is best to cast or size bullets to match or barrel groove diameter or exceed it by 0.001" in pistols. For revolvers, it is best to match the cylinder throat instead of the barrel grooves.

With repsect to shooting 9mm jacketed bullets in a .357 barrel, I have shot 90 grain 9mm bullets from a .357 Magnum revolver. With fairly hot loads, they were suprisingly accurate at 25 yards. If the pressure is high enough, it causes the bullet's base to expand until it fills the chamber throats and that improves accuracy.

SL1

res45 · January 6, 2010, 11:34 AM

I shoot a Ruger BH convertible in 357/9mm so your results may vary. I shoot jacketed,plated and my own cast bullets in both calibers with excellent results. I use the Lee tumble lube designs for all my cast bullets and shoot as cast,the 38/357 cast at .359 and the 9mm cast at .357 using straight WW aloy I don't resize either one and have no leading problems.

I water drop my 357 bullets to harden them for max velocity and let my 9mm air cool so there softer this allow the 9mm to obsturate or swell more under pressure to seal the bore when fired. I also tumble lube my bullets with two light coats of Lee Alox thinned with mineral spirits.

The Tumble lube mold is designed to be shot as cast, while the traditional grease groove mold can be sized as needed and gas checks applied if the mold is designed for those

January 6, 2010, 08:13 AM	#1
preventec47 Junior member Join Date: October 13, 2008 Posts: 104	actual bore size if .38 cal vs 9mm bullets ? years ago my friend cast his bullets for 38 cal and 9mm out of the same mold. I always thusly thought they were the same size ( his of course were ) But recently I find that 9mm bullets are .355 and .38 are .357 caliber. There is two thousandths difference. My reason for asking is I want to shoot a 90gr speer "9mm" (.355) bullet in a 38 or 357 magnum. I wouldnt think that just 2 thousandths would cause the bullet to rattle down the barrel but i could possibly see lower pressures being generated because of a lesser tight fit etc. Anyone ever used .355 jacketed bullets in 38 or 357 pistols ?

January 6, 2010, 11:34 AM	#3
res45 Senior Member Join Date: September 15, 2007 Location: NC Posts: 753	I shoot a Ruger BH convertible in 357/9mm so your results may vary. I shoot jacketed,plated and my own cast bullets in both calibers with excellent results. I use the Lee tumble lube designs for all my cast bullets and shoot as cast,the 38/357 cast at .359 and the 9mm cast at .357 using straight WW aloy I don't resize either one and have no leading problems. I water drop my 357 bullets to harden them for max velocity and let my 9mm air cool so there softer this allow the 9mm to obsturate or swell more under pressure to seal the bore when fired. I also tumble lube my bullets with two light coats of Lee Alox thinned with mineral spirits. The Tumble lube mold is designed to be shot as cast, while the traditional grease groove mold can be sized as needed and gas checks applied if the mold is designed for those __________________ The Reloaders Network discord Channel https://discord.gg/Nafuzht

January 6, 2010, 08:38 AM	#2
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	A couple of things: First, cast lead bullets are typically made about 0.001" larger in diameter than the jacketed versions for a particular caliber. So, 9mm cast are typically 0.356" and 38s are typically 0.358". Cast bullets are often run through a "sizer" to make them a particular diameter (and improve their roundness, in some cases). It would be easy to use the same mold to cast bullets around .0.358 or larger and size some to 0.356" for the 9mm. however, sizing bullets more than about 0.002" can adversely affect accuracy. It is best to cast or size bullets to match or barrel groove diameter or exceed it by 0.001" in pistols. For revolvers, it is best to match the cylinder throat instead of the barrel grooves. With repsect to shooting 9mm jacketed bullets in a .357 barrel, I have shot 90 grain 9mm bullets from a .357 Magnum revolver. With fairly hot loads, they were suprisingly accurate at 25 yards. If the pressure is high enough, it causes the bullet's base to expand until it fills the chamber throats and that improves accuracy. SL1