.40 loaded to same as .45 acp = same power?

RickB said:
If they were sturdy, the power factor for major wouldn't have been reduced from 175 to 165?
Though I doubt there was ever a public announcement to the effect, there was an "understanding" among the membership that major was reduced to 165 because 175 was too hard on .40 guns.
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On Glocks and M&Ps. Yes. But it was more for the 9mm Comp guns in open to be able to make major than it was for the .40s.
 
A bit of drifting around in the thread, but the simple answer to the OP's question is

Equal masses at equal speeds will have the same amount of calculated energy. (both ways).

Shape and size (longer and pointed vs. short and blunt) plays a part when the bullet penetrates material but does not change the calculated energy.
 
Has anyone taken a 45ACP case and necked it down to 40, (ala similar to the 357 SIG). I wonder how well that might do.
 
200 grain bullets are not recommended for the 40 because of the taper inside the case. You may get rounds that can't chamber and you may be more likely to spike pressures due to limited case capacity. I would just load the 180s in 40 to the same speeds as 180s in a 45 if you want to match power. 40s operate at a much higher pressure as well. Something like 17000psi vs 33000psi.
 
And why push it, what is a 200gr .40 cal going to do that a 180 won’t do, especially considering the extra velocity.
 
Give the same bullet weight and velocity they would have the sane energy. Recoil might be slightly different due to the increased bearing surface of the 40cal bullet. And due to the oncreased sectional density the 40cal would penetrate better.
 
Shadow9mm said:
Recoil might be slightly different due to the increased bearing surface of the 40cal bullet.
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Does this mean the 40 would have more or less recoil than the 45?

And how does bearing surface contribute to recoil?
 
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74A95 said:
Does this mean the 40 would have more or less recoil than the 45?

And how does bearing surface contribute to recoil?
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In theory, as i understand it, my thought process is this. increased bearing surface would mean increased friction, both in starting and while traveling down the barrel. Increased friction means you need a harder push, more energy, to get the bullet to the same velocity. More energy means more recoil. Would it be noticeable to the average shooter? Somehow i doubt it. But as i understand it, yes there would be more recoil.

However i made an oversight in assumingthe bearing surface area on the 40cal would be larger. While the 40 cal would most likely have a longer bearing surface, the over all area of the bearing surface could be the same or less than the 45 based on the reduced diameter of the 40cal bullet.
 
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Yes, I was going to bring that up, that the bearing surface would not necessarily be larger because although maybe a longer surface as to the bullet length, the circumference of the larger .45 would make the bearing surfaces pretty close in size.
Not a math wizard, so I didn't take the time to calculate this.
 
I found an article that compared recoil of same weight bullets (200 grain) in the 40 and 45. When using the same gunpowder, which is critical for a same-to-same comparison, it shows the 40 produced less recoil than the 45. The reason is the 40 requires less powder to push the 200 grain bullet to the same speed.

https://www.1911addicts.com/threads/recoil-comparison-pistol-cartridges.25116/

It's in post #2, click on "see more". Look for Table 5 and the figure just above it.

"The 200-grain bullets in .40 S&W produced 5.3% less movement than the same weight in the .45 ACP (pictured below)."

"Why does the same weight bullet produce different amounts of recoil in different calibers? Once again, a major player is the amount of gunpowder required to reach the same velocity. In this case, the larger caliber required more gunpowder to reach the same velocity."


Also, a similar comparison was made between 38 Super and 45 Auto with the same weight bullets. The smaller diameter 38 Super required less of the same powder and therefore produced less recoil than the 45. Look for the "160 grain Accurate #7 No Compensator" figure.

https://www.shootingtimes.com/editorial/compensated-45-vs-compensated-38/99515
 
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excellent, thanks for doing that research.
Wonder what powder they were using in post 2 for the 200 grain tests of the .45 and .40
That seemed like quite a difference in the amount of powder needed for each to push the same weight bullet.
But there you go. Smaller pistol, same recoil essentially, same power factor, and less powder in the .40 to .45 comparison.
 
In post #1 they say handloads were done with Ramshot Silhouette.

"Handloads
The limitation of comparing factory ammunition (unknown gunpowder) can be solved by using the same gunpowder in handloads. Ramshot Silhouette gunpowder was loaded with the same bullet weights as the factory ammunition (Table 3). Three different charge weights were loaded for each bullet to allow analysis for a specified velocity with linear regression. For this analysis, the Ransom Rest movement was calculated for the same velocities produced by the factory ammunition."
 
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