K40 ammo

[JackRyan]

Was just wondering if anyone knew for certain that the K40 is made and advised to shoot hot heavy loads. Like Underwood and Buffalo Bore? My guess is that the K40 can handle these hot loads with ease. Also is the Kahr K40 barrel “fully supported” ? Thanks in advance

[JackRyan]

Guess not. I’ll call Kahr and report back.

[topgun1953]

Was just wondering if anyone knew for certain that the K40 is made and advised to shoot hot heavy loads. Like Underwood and Buffalo Bore? My guess is that the K40 can handle these hot loads with ease. Also is the Kahr K40 barrel “fully supported” ? Thanks in advance

I believe Kahr manuals say +p is fine. Don’t know what supported barrel is...but I’m not an expert and I didn’t google it yet. 😀

[Scott321]

Are you reloading? I don't know if it would make much difference otherwise.

Although it's not the fancier K barrel, comparing my CW40 chamber to my FS M&P40 2.0, the 2.0 has more chamber support, but the fit is tighter on the CW40 chamber. The CW40 has a slight crescent shaped reduction in chamber support from about 3:30 -5:30 position, with the widest part of that crescent at 4 o'clock is about 2/3 of a mm compared to the M&P. I don't notice any bulging on the cases at this point, and I'm pretty sure that Glock's have even more unsupported. However, the smaller you go, the more exact things tend to be, and you have limited space for things like slowing down a slide before it slams into the stop.

Although I know that Underwood has a reputation for hotter loads (particularly in the around 100 year old 9mm, 45 ACP, 357 magnum, etc.), I don't know how much more they offer in 40 S&W. For example, Remington's bonded GS line lists their 165gr 40 S&W at 1150 fps w/ a 4" barrel. Underwood lists it's 165gr JHP at 1200 fps (I didn't see a barrel length). That's only 50fps more. More, yes. How much more related to what one 40 vs another can handle, I don't know.

Buffalo Bore has a "40 +P line" as well as a standard pressure line. BB lists their 180gr "+P" 40 S&W loads at 1100 fps. This is about the same as the Remington 185gr +P GS 45 ACP which I use in my CW45. I don't know how much the difference the ~2oz difference in slide weight makes, but my CW45 seems to do fine with the +P GS's.

That being said, I would advise changing the recoil spring per manufacturer suggested intervals (I think it's around 2000 rounds), and although the metal frame might mitigate perceived recoil, that little gun is still going to be given a work out if you shoot a lot. I'd also keep an eye on the cases and look for any signs of wear over time. If you're looking for more velocity/power, I might suggest either a longer barrel, or different caliber, e.g. 10mm, 357 Mag, etc. I'll add, that although I don't have a K40, the T40 handles the 40 pretty well, IMO (as well as other FS 40's). The longer barrel might also help increase velocity and power if that's what you're going for.

[berettabone]

A steady diet of hot loads wil advance the age of your firearm regardless of manufacturer...…...………………...

[JackRyan]

I have a lot of Underwood 165 and 155 gr loads. i very rarely hear +p or +p+ when talking about the 40 S&W. saami specs usually are more related to chamber pressure. So 40 already being a higher pressure round, rarely gets the +p rating. I would rather the round be tighter fit vs completely inched and loose. i did load when I shot for exacting accuracy, but now I just want to shoot anything market based. I usually shoot everything but practice carry shooting with hot underwood 165 and 155. i get amazing results with my extended K40 barrel that are near 600 ftlb energy levels. i bought the Kahr because Glock chambers are loose spec and my PM9 was a real tack driver. I have come to love Kahr’s Thanks for the replies.

[JackRyan]

i have done a lot of research on the 40S&W. I love that round. It was never actually designed with forethought but to bail out ammo Mfg. The 10mm flopped. they all had tons of 180 boolits and no caliber/chamber to market sell. So they just mish mashed the 180 gr 40 S&W and promoted it. After years of development, it is still the number one used among police. BUT the secret is that the old 40 is more suited to 155-165 grain lead. Not the 180 gr that causes over pressure. I have always used the lighter boolits in the 40 and have found out why many pro/comp shooters use the 40 S&W.

[berettabone]

The .40 round has always been my favorite. It seems like 10mm is making a resurgence, at least in my area. Lots of requests on different gun sale sites to make trades for a 10mm.

[Bawanna]

The 40 is just a detuned 10mm. The FBI not happy with the 9 wanted the 10. At the time the guns of the era couldn't handle the pressures so a little detuning and you have a 40. It was also not fun for small statured and female agents.
Now days I believe the 10mm is coming back, the 40 seems on the way out. All the agencies in our area are now going back to the 9mm. More capacity. Kind of a large circle. Took me 15 years to get 45's in our officers holsters after starting with 9, then 40. Ours are still issued 45's but if they desire they can purchase a 9. Part of that is the sudden urge for red dot sights which can easily be installed on the 9 Glocks but not the 45's yet, that and holsters are always behind on the real caliber guns for some reason.
I like the 40 in a full size gun although I don't have one and probably won't get one. I have a K40 but it's a safe queen and will likely stay that way.

[KahrK40]

There is a wide range of support for chambers. Kahr chambers are considered unsupported. This means an amount of the casing is sticking out past the feed ramp, but just on the button of the casing, whereas the top and sides are supported. A fully supported chamber completely encapsulates the cashing after leaving the feed ramp, top, sides and bottom.

9mm and 40 S&W both have the same pressure of 35,000psi, and 9mm +P is rated at 38,500 psi. There is no true +P designation for .40 S&W except for a few companies that brand it as such. If the pressures of the ammo you're looking at exceed 38,500psi, "caution should be taken." I don't know what else to say except don't risk it, do research or just be careful.

This video of how effective regular .40 S&W 180 JHP might change your mind. The video is Hornady American Gunner which uses the XTP bullet. The velocity out of a K40 would be 50-75 fps less than in the video. This isn't necessarily the "best" self-defense round but as you can see it still performs.