Difference between 10mm and .40

[Clint007]

I am relatively new to loading 10 mm. I was looking at Longshot and the Hornady XTP bullet. That at least as I interpreted it, the 10 mm velocity's are only about 150 ft./s faster than the 40 Smith & Wesson, on the Hod Website...This is for near max load.I was under some general impression that 10 mm was considerably stronger than 40 Smith & Wesson I was expecting to see a different velocity difference at max load.

Does this ~150 FPS difference really translate into more impact oomph than it seems?

C

[The_Shadow]

Well all things considered yes 150 fps difference is probably on the lower end of performance gains between 40S&W & 10mm.  The case capacity is diminished by about 1/8" in length in the 40S&W.
You also have to consider the SAAMI max pressure values as well.
10mm being 37,500 psi and 40 S&W being 35,000 psi.

Barrel length can also play into the velocity performance.  For shorter barrels you might see the 40S&W loaded with faster burning powders, they peak their pressure sooner and work to complete their burn before bullet exits the bore.

When it comes to bullet & powder selection there are many that will yield awesome performance for each of the cartridges.  Then there are parameters such as subsonic that keep performance velocity below the sonic threshold.  That is because of possible close quarter performance which help minimize the pressures on ears during and encounter.

That being said 200 grain in 40S&W might get 900 or even 1000 fps where as the 10mm could push a 200 grain 1240-1260 fps
The commercial 40S&W 180's also are between 980-1010 fps but 10mm could be pushed over 1300 fps

[sqlbullet]

I looked at the 135, 155, 180 and 200 grain data for both cartridges.  When Hodgdon didn't have the data on their site, I used the updated Lee 2nd Edition since Lee sources most of their data from the powder maker.  This means it is an archive of data Hodgdon no longer has on the site for XTP bullets.

Average velocity FPS increase 147.75
Average velocity PCT increase 12.5%

Weight  |	Manufacturer  |	Style  |	40S&W Velocity  |	10mm Velocity  |	Difference  |	PCT Change  |
135	Nosler	JHP	1392	1551	159	11.42%
155	Hornady	XTP	1283	1409	126	9.82%
180	Hornady	XTP	1159	1295	136	11.73%
200	Hornady	XTP	987	1157	170	17.22%

If you expand this data you will note that 10mm has a greater advantage with heavier bullets than lighter ones.

But, velocity alone only tells part of the story.  Remember when looking at energy, velocity is squared, so any gain in velocity had a huge boost in energy:

Average energy increase lbs-ft:  138
Average energy increase PCT:  26.8%

Weight  |	Manufacturer  |	Style  |	40S&W Energy  |	10mm Energy  |	Difference  |	PCT Change  |
135	Nosler	JHP	581	721	140	24.15%
155	Hornady	XTP	567	683	117	20.61%
180	Hornady	XTP	537	670	133	24.85%
200	Hornady	XTP	433	595	162	37.41%

The final comment I have is to re-enforce The_Shadow's comments about 10mm data being not quite as hot as 40 S&W when compared to the velocities that commercial ammo makers load to.

[Clint007]

Thank you

C