45ACP bullet weight vs perceived recoil

[GeoDudeFlorida]

I have never heard of a pistol bullet decelerating in the barrel. Commonly heard of an extra low expansion ratio setup like a .22 that can slow down after say 14" (CCI MiniMag in BBI) but in a pistol barrel with maybe 4" of rifling?

When the Limited shooters found that a 220 gr .40 and quant. suff. Clays FELT soft, they didn't realize chamber pressure was high and were beating up guns.

Isn't a squib a bullet which has decelerated inside the barrel to a constant velocity of zero?
Yes, deceleration happens. Even in a 5" 1911A1 barrel. Excessive deceleration is a stuck bullet.

The forces of expanding gas behind the bullet are acting against many other forces: the weight of the air column in front of the bullet, the frictional forces of the bullet in the barrel, the force of the bullet being swaged down by the chamber throat (remember, in America we call the groove the "bore" and forget all about the actual bore, which is 5-8 thousandths of an inch smaller in diameter than the groove)... The powder burns completely in microseconds and the resulting chemical reactions continue to create gas which expands rapidly - "burns" - forcing the bullet into the bore and groove and down the barrel; but, once the chemical reaction is exhausted, only the gases remain to push against all of those other forces. Once the gas stops expanding - again, all of this happens in milliseconds - deceleration begins immediately. The bullet lacks the mass to counter friction and push the air column in front of it forward.

The math works and so does practical experimentation. Just make sure if you do stick a bullet, you don't send another one after it.

 

[Mostly Lead]

My progression with loading 45 ACP 1911 was starting out with pc lead and FMJ 230 gr with either HP38 or tightgroup. My wife didn’t care for the 230 gr snap, so I switched to a 200 gr plated SWC and a 200 gr plated RN. After fine tuning I am very pleased with the recoil impulse from the lighter loads. )4.7gr HP38 YMMV)

Would I expect to see a similar result going from 200-185? I have standardized with HP38/Win 231 not that it should matter much.

In my loading experience with 9MM it always felt as if the lighter 115 gr had more recoil than 124’s. That doesn’t seem to be the case with 45.

Similar, but not as much. Going from 230 to 200 was a 13% reduction in weight, from 200 to 185 is only a 7.5% reduction...

 

[Jim Watson]

Yes, deceleration happens. Even in a 5" 1911A1 barrel. Excessive deceleration is a stuck bullet.

Can you provide quantitative examples in the realm of real shooting?
If my 200 gr bullet 3.6 gr Bullseye 670 fps at 10 feet is decelerating, what was its maximum velocity? I was not interested in marginals like a powder less stuck bullet.

remember, in America we call the groove the "bore" and forget all about the actual bore, which is 5-8 thousandths of an inch smaller in diameter than the groove)

THIS American doesn’t and neither does SAAMI. Annoys me like “clip” annoys the usual poster.

Once the gas stops expanding - again, all of this happens in milliseconds - deceleration begins immediately

It can’t stop expanding unless the bullet sticks in the barrel.
Maybe somebody with Quickload will calculate some velocity curves and muzzle pressure.

 

[Laphroaig]

I've been loading Hi-Tek coated 185 Buttons and 200 SWC's both with 4.5 gr. HP-38. Both loads barely spit the brass out to the side but function 100%. I like that because I easily find most of my brass. I'm thinking that is about as light as I can go with my pistol.

Note that I have a slide mounted Ultradot and am running a 13# recoil spring. When I had the Ultradot put on I had to experiment with recoil spring weights to compensate for the added weight and function with lighter loads. 13# seemed to work the best.

I feel a definite difference in recoil between the 2 bullets, the 185's obviously are a little bit softer.