No plans to conceal any 6" anything. I brought up 6" simply because that's a common barrel length between them (6" revolver, 6" 10mm and 6" 40). I wouldn't carry a .41 Mag 265gr/1450fps in a populated area, the only purpose for that is essentially to represent full power loads in each.
You speak of SAAMI specs, but I can tell you this that 1400-1450 fps 10mm 180gr is overpressure. Is a 180gr .40 at 1300+? According to Hodgdon, Longshot will do 1150 from a .40 S&W with several K psi to spare. That load from a 4" G23 averages just over 1150, from a 5.3" G35 it's above 1250 fps and from a 6" barrel it is indeed above 1300 fps in a .40 S&W.
I agree that 1300 fps is about the most .40 cal JHP's should be driven...well at least 180gr-200gr. Some of the more shallow cavity Gold Dots like the 155gr and 165gr will hold up to more, but not a whole lot more, 1400-1450 fps for them IMHO.
Not sure where to begin. Handloaded 10mm/180gr JHPs 1400fps+ doesn't necessarily put it it in the over pressure category, but XTPs and Gold Dots certainly fragment at those velocities. Going back about seven years and using Hornady, IMR 800X, load data for a 175gr Silvertip, I got 1398fps, ES 37fps, SD 13fps through a 6" KKM barrel. The Silvertip fragmented so much that I stopped developing the load.
I don't see 6" barrels in 10mm or .40 as being common. I've tested .40 cal JHPs through a CX-4 Storm and found the increased velocity through the 16" barrel overwhelmed JHP designs.
The 155gr/165gr Gold Dots you thought were shallow cavity designs are in fact deep cavity designs. At this time, Speer does not make a shallow cavity Gold Dot in .40 cal. If you look in the upper right corner of the yellow boxes you'll notice the bullet and cavity outline, deep cavity for the 165gr Gold Dot and shallow cavity 125gr GD.
Visually, it's very easy to compare the cavity size differences. Bullet designers increase the hollow cavity area to get hollow point bullets to reliably expand at lower velocities. The blued magazine on the left is loaded with .40 S&W 165gr Gold Dots, a visit to the ATK website will give you all the FBI protocol data for this LE ammunition. The .38 Super, single stack magazine on the right is loaded with 125gr GDs ~mid 1400s.
Since this thread is about using the 10mm for self defense, we'll compare the 10mm with the 357 mag and 38 Super, all running bullets in the 1400s, as close as I could match them.
Shallow cavity 125gr GD @1436fps, 38 Super;
Text book symmetrical expansion, good for about 16" of soft tissue penetration.
10mm is often compared to the .357 mag as having more power, however one describes power. Old tech, exposed lead tip 158gr Winchester JHP, 1437fps;
Another text book symmetrical expansion, slight weight loss, but good for about 20" of penetration. Sectional density of this bullet is about the same as the 10mm 200gr.
Now, 10mm 155gr Gold Dot, 1420fps;
Deep cavity Gold Dots don't perform well at velocities designed for shallow cavities, in this test, recovered weight was only 132.9grs. Bullet also over expanded, think opening a parachute, plus, the loss of one petal would likely cause the bullet to tumble. Penetration good for ~8.6".
For 10mm handloading, I target JHPs to 1250-1265fps for reliable expansion at personal defense distances. The exception to this being the 125gr/155gr Barnes bullet, I'll be testing Double Tap ammunition soon.