Why is the .45 ACP more accurate than other duty calibers?

[BehindBlueI's]

SLG mentioned this in another thread, and instead of cluttering that up I figured I'd ask here. It jives with my own experience, but I just chalked it up to shooting single stack better or the general awesomeness of the 1911 and Sig P220.

So, why is the .45 ACP more inherently accurate than .40 S&W?

[JCS]

Is 9mm a duty caliber as well?


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[LtDave]

100 more years of load development?

There is quite a bit of interesting info on loading accurate 9mm match ammo at the Bullseye-L forum. The Enos forum probably has the most .40 S&W info.

[JCS]

100 more years of load development?

There is quite a bit of interesting info on loading accurate 9mm match ammo at the Bullseye-L forum. The Enos forum probably has the most .40 S&W info.

Thanks for sharing. Going to check out that forum for 9mm


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[Hauptmann]

SLG mentioned this in another thread, and instead of cluttering that up I figured I'd ask here. It jives with my own experience, but I just chalked it up to shooting single stack better or the general awesomeness of the 1911 and Sig P220.

So, why is the .45 ACP more inherently accurate than .40 S&W?

Pressure. In its standard config, the .45acp has a relatively low operating pressure. So, its brass case is thin and soft allowing for a good gas seal. Higher pressure cartridges like the .40S&W need a thicker case wall to contain the pressure, and that can result in an inconsistent gas seal. The second problem with the .40 is that at those higher operating pressures it can warp the bullet as it exits the barrel resulting in fliers and bigger groupings.

So the next question is, why do some higher pressure cartridges like the .357sig have good accuracy. Well, the case shoulder on the bottle neck helps to seal the gas a little better than a straight walled case, and the bullet is a smaller caliber. A .40 and a .357 have the same bullet jacket thickness.....whether it be FMJ, JHP, or copper plated. So, the .357sig bullet has a greater jacket to soft lead core ratio....making it a stronger bullet better capable of handling the higher pressures. The tapered case on the 9mm helps with gas seal, as does the good jacket to core ratio.......so it is a pretty accurate caliber too.

Some of the most accurate .40S&W loads I have shot have been either solid copper DPX bullets, or sinter fire copper frangible bullets. Neither of those bullets warp, so that eliminates an element of inconsistency for the caliber.

[45dotACP]

JMBs ghost nudges the bullets in flight so they go into the ten ring more often

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[Lon]

JMBs ghost nudges the bullets in flight so they go into the ten ring more often

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Yep. Because John Moses Browning was a frigging genius.

[Velo Dog]

According to Winchester's spec sheets, the 9mm is capable of the best 50 yard groups of their law enforcement offerings.
http://winchesterle.com/Lists%2FCata...2FRA9124TP.pdf
The .45ACP is more consistently accurate, however.
http://winchesterle.com/Lists%2FCata...15%2FRA45T.PDF

[Wheeler]

Pressure. In its standard config, the .45acp has a relatively low operating pressure. So, its brass case is thin and soft allowing for a good gas seal. Higher pressure cartridges like the .40S&W need a thicker case wall to contain the pressure, and that can result in an inconsistent gas seal. The second problem with the .40 is that at those higher operating pressures it can warp the bullet as it exits the barrel resulting in fliers and bigger groupings.

So the next question is, why do some higher pressure cartridges like the .357sig have good accuracy. Well, the case shoulder on the bottle neck helps to seal the gas a little better than a straight walled case, and the bullet is a smaller caliber. A .40 and a .357 have the same bullet jacket thickness.....whether it be FMJ, JHP, or copper plated. So, the .357sig bullet has a greater jacket to soft lead core ratio....making it a stronger bullet better capable of handling the higher pressures. The tapered case on the 9mm helps with gas seal, as does the good jacket to core ratio.......so it is a pretty accurate caliber too.

Some of the most accurate .40S&W loads I have shot have been either solid copper DPX bullets, or sinter fire copper frangible bullets. Neither of those bullets warp, so that eliminates an element of inconsistency for the caliber.

The .38 Special and .357 Mag are both straight wall cases and capable of excellent accuracy, as is the 10mm.

It's been my experience that heavier bullets require less velocity to acquire stabilization. They are also less prone to be affected by crosswinds. The biggest problem with the .40 is it was originally designed to be the 10mm lite load with a 180 grain bullet at 900-950fps out of a 1 in 16" twist barrel. The bullet doesn't stabilize well. Tests have shown that it performs much better out of a 1 in 14" twist rate barrel. The case volume is too small to safely increase the velocity out of the 1 in 16" barrels to achieve stability. The 165 grain loads pushed to 1050-1100fps have a much greater accuracy potential, less pressure fluctuations and are safer to shoot than the 180 grain loads.

Pressure seals in the chambers are not as important in pistol cartridges as in bottlenecked rifle cartridges. For instance, a 158 grain .38 Special running at 700-750 fps is a superbly accurate load and shows all the signs of low pressure or the case not expanding to completely seal against the chamber. The .32 S&W Long is another example of an extremely accurate cartridge that doesn't seal the case against the chamber walls.

[TiroFijo]

The gunsmiths that build super accurate competition 1911s report that the 9 mm has an edge in extreme accuracy.

In normal guns, I've never seen a difference between 9 mm/40/45. Perhaps because I reload 90% of my ammo.