The reason I posted the question about the 40 s&w is because the handgun I decided to purchase(hk usp compact) comes in both the 40 and 45acp calibers. I have owned 45's before so I don't think recoil would be much of a factor. Which do I choose?? I also think you can get magazines for either caliber that hold about the same number of cartriges. I know the 45 acp comes in p+, does this lead to a dramatic increase in stopping power?? Once again, your assistance is needed.

First of all let me congratulate you on your choice of what I consider the best carry weapon ever made. The USP is slightly too large for my hand, but the USPC fits me like a glove. Either will feed any type of ammo you care to throw at it and you won't need a trigger job or any other work to make it 100% reliable with anything you care to shoot. I carry the .45 ACP and with 2000+ rounds through it of every type you can imagine, I've yet to have that first failure of any kind. Of the 4 HK pistols that get shot regularly, we have over 7,000 round and still not that first failure of any kind. Next, with either round you will have an excellent self-defense weapon. I like the .45 ACP round and I am not ashamed to admit an extreme prejudice toward it. It carries the same energy levels as the .40 with +P .45 loads and it shoots a bigger, heavier bullet. Now, there are two things the .40 can do the .45 cannot. One, the .40 holds ten rounds, the .45 ACP only holds 8 (magazine), but be honest, how long a gun fight you plan on being in? Also, with the .40, if you want, you can buy either a HK or Jarvis .357 SIG barrel and have two guns with only a 30 second barrel change. The same mags work perfectly in the USPC for both calibers, as does the recoil spring/guide assembly. To me, those are the only advantages the .40 USPC has over the .45 USPC. The .45's ammo is cheaper too and is available in a wider range of weights from 165 gr. to 230 gr. Accuracy is equal in both, that is, more than likely more accurate than most shooters. My compacts (6) turn in 5 shot 25-yard groups that usually go 1.5 inch (from a good rest), but quite often less. That tells me it is not the gun that is the limiting factor, but my tired old eyes.

Check in over at HKPRO (hkpro.com) for more information. Doc-Rat designs is getting ready to market a +2 base pad for the .45 ACP USPC that will bring up the mag count to 10 rounds. As I am sure you know, standard USP mags will not fit the USPC.

Got an easier rule. IF two calibers are offered in the same size platform, will take the larger.

If they make it in 10mm that would be a better choice then the 40 caliber. IMHO

Not yet. Hk has not entered the 10mm field except for a limited amount of MP5/10 smgs. If interested in a 10mm sub machine gun you can read about it here. (http://www.hkpro.com/MP5-10.htm)

hk guns should stand up fine. i don't own them, but i have shot them before at the rental place. i remember shooting 500 rounds of walmart cheapy in a 9 mm hk a few years ago. i just shot it and shot it and shot it some more without resting or anything. the gun just shot and shot and shot like battle guns suppose to do.

i don't know many semiauto pistols can do that for more than 100 rounds without a malfunction. i have heard many kimber malfunctions, which i think are either false claims or very very very poor manufacturing flaws. guns should not malfunction in this day in time, especially when they are 1911 model. people had almost 100 years to fine tune what sir browning produced, and his production is pretty close to perfect.