My understanding is that most of the guys in the top ranks are shooting 1911 varients, in .40S&W.

1) .40 is considered a "Major" caliber (power rating)
2) Capacity

JW

I shoot IDPA with a 9mm. It is much cheaper and follow up shots are quicker. On rare occasions, those with 9mm had to hit the popper twice for it to fall down. We use the popper maybe once every 3-4 months. I aim for the upper 1/3 of the popper and never had it not fall down.

The 40 punches cleaner holes and the 45 makes bigger ones. But if you're relying on near misses then you just need to shoot better.

Magazine capacity is not an issue with IDPA as the rules define how many rounds per magazine.

Shooting major is a definite advantage in IPSC scoring which requires .40 or greater for major.

If you can shoot all A's then the, minor, 9MM will suffice.

If you are concerned about ammo cost go 9MM.

It's fun either caliber.

For USPSA, which caliber you want really depends on how much you are willing to spend.

If you're thinking under $1k, I'd suggest one of two options
1) A 9mm semi to put yourself in the production class. There is no benefit in production class to have bigger bullets.
2) A 1911 in either 9mm or 45acp to compete in single stack. Here there can be a benefit to shooting bigger bullets.

If you've got around $2k, I'd suggest something with a high capacity in .40S&W. This will let you play in Limited.

If you've got $3k, then go for a high cap .38 super 1911 to play in open class with a gun that'll end up looking like something out of a Sci-fi movie.

I don't know much about IDPA, so I can't help you there.

Which ever one is the most affordable to you and which ever one you shoot the best

Starting out for USPSA... go Production Class, and shoot any good 9mm gun of your liking. The longer the barrel/sight radius the better. Everybody in production shoots 9mm. (The same gun can be used in IDPA, and a 3" barrel is nice for a "real" carry gun, but a liability in competition) I'm buying a M&P9 Pro Series (USPSA legal by Jan 1).

If you decide to move up, in the limited, and open classes, the new rage is a 9mm "Major" gun. The rounds are handloaded to EXTREME pressures with the newer powders, and the bullets are seated barely into the case mouth. They look funny... (A few are still shooting 38-Super, but you get more mag capacity with the 9mm-Major. I saw ZERO 40s in Open Class)

They are shooting 124 gr jacketed hollowpoints (the round noses have open bases to the bullet, which at extreme pressures leads the barrel badly). To make major (165 power factor= weight of the bullet X velocity / 1000), you have to push a 124 gr bullet over 1330 fps!!! That is a +P++ 9mm load, requiring a very strong chamber, a 7" barrel, 5" inside the slide, and a 2" heavy ported tip to control flip. The guns have 28-30 round magazines, custom built for the LOOONG 9mm rounds. They are HEAVY and all steel. They are all wearing red-dot optics, mostly "C-More" brand. Standing anywhere within 25 yards of these guns without good ear muffs will deafen you pretty fast!

I got to shoot one for half a dozen rounds. Felt like a 22 magnum... and tore ragged holes at 10 yards... I'm sure it's 1" capable at 30-40 yards in the owner's hands... It was a $4500 custom gun.

Fun stuff, for the cost of a decent used car...

A FEW traditionalists are shooting stock 1911s in Single-Stack class, but I think it's a dying breed in USPSA and IDPA.

Jeff

Caliber in IDPA, or IPSC dictates your major or minor category. Anything below 40S&W is minor, above is major. Production class with 9mm would be in your best interest to start out IMO. More experienced, go limited 10. get the experience no matter what. You;ve got to go and be a newbie at least once. Watch and learn. Most of the folks at my club are more than helpful. Be careful, you may get a new addiction.

Originally Posted by Ram Rod

...Be careful, you may get a new addiction.

No exaggeration here! Replace the word "may" with "will" and it will be a more accurate statement.

Unfortunately, there are a lot of factors in deciding what gun / caliber to go with.

Fortunately, the simple answer is '9mm and shoot in Production'

Production (in USPSA) is the entry level. The only caliber you'll see is 9mm because there's no bonus for shooting a larger caliber. Production also limits what modifications you can do to your gun, so you won't be shooting against people with optics and compensators. Both of these things mean that you can shoot ammo that's cheaper and use a gun that you didn't put hundreds of dollars of aftermarket parts into.

Unfortunately, I don't know about IDPA. There's only one IDPA match / month around me, but there are five USPSA matches / month. I'd recommend you check out the rulebooks and see how the equipment rules affect what you'd like to shoot and what you'd like to stay away from.

I am going to try IDPA with 45ACP because that is what I normally use.