Kahr K vs. MK, 9 vs. .40


April 13, 2012, 03:48 AM
Howdy all! I'm new here, so I'll give a quick background: I grew up in a relatively rural area, handled rifles and single-action revolvers. Purchased an HK P30 in .40 a couple years ago, and carry it regularly. It conceals well Inside-Waist-Band with most clothing, but during the summer I'd like something smaller; still planning for IWB, not pocket carry.

I've narrowed my sights down on the K9 (or 40), or possibly the MK9 (40). I've already ruled out the polymer Kahrs as the weight of the K isn't too much at all, and the grip is so much better. I would have considered a baby Glock, because I would love the way my friend's G20 shoots if the grip didn't feel like a rough brick -- that goes for every Glock I've held, so they're out, too. I really like the feel of Beretta's PX4 compact, and the rotating barrel intrigues me, but it's not enough smaller than the HK to justify it being my next purchase.

Lots of people say the .40 kicks too much in the small Kahr -- I had a chance to try out both a K40 as well as a P40, and while they were snappy, they certainly weren't painful or unmanageable. (I must admit, though, compared to them, shooting the HK felt like a gentle massage.:)) I haven't been able to try a Kahr in 9mm, nor have I shot many 9s. I've probably put 30 9mm bullets downrange in my life.
So I have two dilemmas:
1) K vs. MK. I'm pretty set on the K, because it's still tiny and the grip is so nice, but if anyone has compelling reasons why the MK is preferable please let me know. Is it really much less concealable or more comfortable for IWB in shorts and T-shirt? (I'm 5'11, 180 lbs, and the HK does well with at least 50% of my shirts.)

2) This is practically the 9 vs. .40 war, so skip this if you've had enough of it. Clearly, shot for shot, the 9mm is not more effective than the .40. That is, if e(x)= effectiveness of cartridge x, e(9mm)<= e(.40). If e(9mm) = e(.40), then 9mm is the obvious correct choice, as it is much cheaper to shoot, has less recoil, and allows higher capacity (in the Kahr, that is only 1 extra). But if e(9mm) < e(.40), which is very possible, I must ask by how much, and is it worth sacrificing the extra round? How to measure it?

Velocity doesn't mean everything, since heavier bullets penetrate better, even if slower. Energy and momentum are so miniscule, I ask myself whether they mean anything. Consider that 500 ft-lbs of energy (more than most semi-auto loads) is about enough to raise 1 cup of water by 1 degree Fahrenheit, or about as much energy as you use to take three walking steps. This is already such a small amount, I can't imagine 500 being meaningfully better than 400, or 200 (.380 ACP) for that matter. Momentum is obviously negligible, by Newton's third law.

I've spent hours researching ballistics charts for various calibers, read countless useless caliber war threads filled with lots of opinion and very little fact, studies that are mostly useless (*cough* Marshall/Sanow) and ultimately it seems the only objective, scientific data comes back to the FBI and penetration being the #1 most important factor in the elusive effectiveness equation, with expansion being a distant 2nd. If this is true, all the numbers boil down to penetration predictors, and it seems 9mm again is the best choice, for the reasons listed above, as the big three semi-auto calibers all have similar penetration/expansion in gelatin.

But defensive loads exist for the .380 that achieve almost as much penetration as the others, with good expansion, so why is the .380 not included as just as viable a choice? Perhaps because, even though ballistic gelatin approximates the body most accurately of substances that could be tested, it might still be marginal at best. Maybe, when striking bone for instance, the extra weight of a .40 makes a larger difference than the inches of gel suggest?

So this is the long thought process that has finally led me to strongly consider 9mm (even though it'd be convenient to have both my pistols shoot the same stuff), simply because it's cheap, with higher capacity than .40, and if the FBI's standards are to be believed, and ballistic gelatin is truly applicable to reality, modern 9mm is just as effective as .40, although I'm becoming agnostic about the quantifiability of projectile effectiveness.

Do any of you have knowledge of or links to sources that scientifically discuss the real basic elements of effectiveness? Penetration, expansion, mass, velocity? The correlation of gelatin with real shootings? After all my research, I'm pretty set on 9mm, but I still really like the .40, and more power does mean something (whatever that is), which makes me feel better. So I'm still open to being swayed back to .40.

Thanks in advance for any answers and information, and, if you made it this far, for bearing with me. This is my first post, so I figured I could make it a little longer. :)
Final thought: I like the DA/SA of the HK, and with the long, heavy pull for DA, I'm completely comfortable carrying as I should, with one in the chamber. I'm a little nervous about the light trigger pull on the Kahr -- any advice or stories about that? Thanks again!

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April 13, 2012, 07:34 AM
If the intent is carry, I'd also consider the polymer Kahrs, but for the purpose of picking one of the selections, I'd choose the black K9. It seems to have possibly the best reputation and black just looks right on a carry gun. Add a CT laser and night sights and there's not much more to ask for in a dedicated CCW, IMHO, (except lighter weight).

April 13, 2012, 07:51 AM
i am a Kahr fan , i carry a PM45 daily. the .45 acp snaps less and is more comfortable to shoot than the .40 S&W out of those tiny Kahrs. IMO i would consider the .45 acp.

April 13, 2012, 11:07 AM
I carry the K40 stainless and I absolutely love that gun to bits.
I shot a friend's K9 and the recoil was much softer than the K40. In fact, I'd go so far as to say that 9mm is a very soft shooting round out of the K9.

I carry the .40 because it's either going to be the same effectiveness as the 9mm, or posibly better. But there's nobody saying that the 9mm is more effective. So, if there is a chance I can give myself the edge, why not? I, like you, am agnostic about the quantifiability of ammo effectiveness. There are too many variables. So I thought I'd give myself that little bit of an edge because it's certainly not gonna hurt.

April 13, 2012, 12:40 PM
I owned both the MK9 and K9 and I would choose the MK9. For me the longer grip did make it more difficult to conceal. I guess I shouldn't say it was difficult to conceal but not as easy as the MK9. No matter what you choose your getting a great gun. I two would stick with the steel guns, much nicer IMO.

April 13, 2012, 02:21 PM
I have an MK40 Elite and love it.

April 13, 2012, 02:33 PM
The K9 gives a more solid feel in your hand, as it allows you to get all of your fingers around the grip. I prefer the 9mm over the .40, but that's entirely personal preference.

April 13, 2012, 02:50 PM
I have both the K9 and K40 when they first came out.I like both pistols alot.The K40 will have "snappier" recoil but stick to 180gr and its very controllable,the light weight 155 and 135s are nasty.The pistols are very accurate and have been extremely reliable with factory ammo.You have to be careful with reloads on OAL and smoothing out any guppy belly brass.

April 13, 2012, 03:43 PM
I went with the 9mm kahr simply so I can have more rounds. I carry the biggest 9mm mag kahr makes for a reload, which sticks out quite a bit...but if I need a reload, I want the biggest I can get. Plus, the biggest one they make is roughly the same size as a 1911 mag.

April 13, 2012, 03:50 PM

But if you get a chance check out the Walther PPS in 9mm

April 14, 2012, 02:21 AM
Thank you all for your responses. If nothing else, it feels good to know that I can't go wrong in this decision! :)

April 14, 2012, 03:42 PM
Owned the P9 and MK9. Great guns. I'd run the PM9.

The Lone Haranguer
April 15, 2012, 12:07 PM
I voted for the stainless K9, but the only real difference between it and the black K9 depends on your personal taste in its appearance. On a CCW pistol there is no real need for a non-reflecting finish, IMO. I don't like the bark and bite of .40 caliber in small guns like these, and the MK series is neither fish nor fowl - not substantially easier to carry belt holstered and a little heavy for pocket carry. I like the PM or the newer CM9 for that. While you're at it, get night sights. :)

April 15, 2012, 12:57 PM
I would (and did) choose the MK9. It will give you the option to pocket-carry if necessary given your summer clothing choices. (I don't particularly endorse it for every day pocket carry -- it does get a little heavy that way. But it can be done.)

If this will never be a factor (committed to ALWAYS IWB,) then K9 will probably be just fine.

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