Because math

[YVK]

Saw this on another forum. I've got nothing, but the last sentence' conclusion is highlighted by me. I need to recheck my lead levels, I seem to unable to follow logical paths anymore.

I agree with the posts here. "Bore Axis" does contribute, but it is quite overrated. Unless the hand sits very low and/or the barrel sits high, then you will have appreciably more felt recoil as a "flip", but most high quality firearms are so well designed, it's not an issue. The weight of the slide vs the springs (reciprocating mass) and the height of the rails all contribute. And regarding the weight of the slide goes, that is also related to how that compares to the weight of the frame. I've heard of people selling quality guns because they had "too much recoil", only to shoot the same gun and have very little. There is an actual equation for how much a gun recoils as a total "recoil factor". The recoil is the SAME on a gun with a certain weight vs the velocity and weight of the bullet, but how it is felt is the issue. This is why GRIP is such an issue.

vgu = {(mp • vp) + ( mc • vc)} / mgu • 7000 → Etgu = mgu • vgu2 / 2 • gc

Where:
Etgu is the recoil energy expressed in foot-pounds (ft·lb).
mgu is the weight of the gun expressed in pounds (lb).
mp is the weight of the bullet expressed in grains (gr).
mc is the weight of the powder charge expressed in grains (gr).
vgu is the total forward velocity of the gun expressed in feet per second (ft/s).
vp is the velocity of the bullet expressed in feet per second (ft/s).
vc is the velocity of the powder charge expressed in feet per second (ft/s).
gc is the dimensional constant and is the numeral coefficient of 32.1739.
7000 is the conversion factor to set the equation equal to pounds.

HK p30 has a factor of: 5.23 ft-lb
HK VP9 has a factor of: 5.39
Glock 19 has a factor of: 6.54
Sig p226 has a factor of: 4.41
CZ P-01 has a factor of: 5.02
CZ SP-01 has a factor of: 3.68
M&P Shield has a factor of: 6.95

Sig p220 in .45ACP has a factor of: 8.29

This shows recoil is not that big of an issue for 9mm. The biggest difference in power factor between all these guns is 138,000 (shield) and 144,000 (SP-01). Which shows 9mm ammo is pretty effective from all barrel lengths.

[orionz06]

So the comment on grip is pretty key here. I feel like the recoil of the Shield isn't as bad as a P30 despite the 32% increase... How it's sprung matters, as well as how one is able to grip things. It looks like that equation only covers an energy, not how it is applied.

[ToddG]

Is "vgu is the total forward velocity of the gun expressed in feet per second (ft/s)" supposed to say ammunition or projectile?

If it is supposed to be gun then I assume he means slide, since the gun as a whole doesn't move forward.

I'm all for math, but this one looks like smoke and mirrors. While I'm not a huge believer in the monstrous importance of bore axis height angle chicken blood, I didn't see anything in the equation that takes any of that into consideration whatsoever. So I'm not sure how it proves that bore axis is unimportant.

Where does the equation account for the difference between wet, bloody, smooth wood grip panels versus heavily textured dry ones? Or does that not make a difference?

I'm confused.

How much does a gun recoil? Shoot it and find out.

[CCT125US]

Needs more math... what about the shooter's mass behind the gun, the relative percentage of how that mass is applied through grip? Why can top female shooters and those smaller statured men who shoot at a high level, out perform others? Is it because the choosen gun recoils less, or perhaps through the application of a better technique? How can that be measured? As TLG said, what about the texture and angle of the grip? So it either needs more math or the realization that individual perceptions and techniques shape one's reality.........

[GJM]

I found it interesting that HK said the following in the brochure introducing the VP9:

Higher grip saddle translates into lower effective bore axis; means quicker target acquistion, less felt recoil, and faster follow up shots

[JodyH]

I found it interesting that one of the H&K brochures had the bullets loaded backwards in the magazine.
Brochures aren't technical manuals... they're ad copy.

[CCT125US]

I found it interesting that HK said the following in the brochure introducing the VP9:

Higher grip saddle translates into lower effective bore axis; means quicker target acquistion, less felt recoil, and faster follow up shots

Because marketing.... did you find that to be true? FWIW I have not fired a VP9.

[PPGMD]

I see no where mentioned in that "equation" slide weight, cg of slide, cg of gun, spring rate, and gun type (striker guns slow the slide going forward, while hammer guns slow the slide going back).

There are so many factors in perceived recoil that it isn't funny. And bore axis is just one of them, and you would need a huge change for it to be noticeable ceteris paribus (yes that is commonly used in economics but I feel like using it).

[orionz06]

I'm no firearms engineer (is that a thing?), but dude is doing a conservation of momentum calculation to determine the velocity of the "gun". He then uses that to calculate the kinetic energy of the recoiling gun which he equates to "recoil". Too many many unstated and, most likely, incorrect assumptions going on there.

This is what happens when people use the internet to "learn" things like physics.

The equation looks similar, if not the same, to one I was looking at in a trusted reference to determine recoil forces for another project. It may not be wrong, just the assumptions and what not. Plus that whole omission of all sorts of other things that matter.

[MGW]