Originally Posted by RogerThat

... I have a hypothesis that the smaller round ... is the least likely to jam...

Actually, no. If this were true the 22's would be the most reliable semi autos (next to the 17's). But nothing could be further from the truth. If anything, the opposite might be true. I find the most problematic calibers to be the small calibers, such as 22, 25, 32.

But more important than caliber is the quality of the gun.

Originally Posted by RogerThat

I know which caliber to use is very controversial, but what I've been wondering is which caliber is least likely to failure to feed. I have a hypothesis that the smaller round (being the round it self would be responsible for the failure) is the least likely to jam. Than again this is just that a hypothesis. I was wondering if anybody has some insight that they could share on the issue. Thanks in advance guys

Your hypothesis is flawed, I've seen more jams from .380 that a .45, it's not the cartridge, it's the gun in question. It's not even a make/model thing as I've seen same makes and models where one will run like a champ and others won't.

My Kimber .45s ran super, my Kimber .40s were horrible, My 5" 1911s have been flawless, my Llama MiniMax .45 was a jam-o-matic. All of my Paras ran ultra reliably in three differnent sizes in .45 and .40...

I could go on and on (too late) but to reiterate "the smaller round (being the round it self would be responsible for the failure) is the least likely to jam" is incorrect.

What's your hypothesis based on?

I have had more FTF's with a 22 than any 9mm or 40 that I have used.

Also VAMarine and JamesNM make a good point - I purchased a new black rifle 6.8mm and tried to run some rounds through it standard Remington and FTF's. Come to find out the rifle was set up to fire military rounds which is OK, a little hotter than commercial stuff - I changed out the buffer spring, reduced the buffer from an H3 to an H2, and no more problems.

Point is it is not always the ammo or the caliber that can lead to FTF's.

FTF's can also happen if you're not used to a gun's recoil. For example, the first gun my girlfriend ever shot was a Sig. First shot was fine, next shot the gun jammed. Cleared it, fired, first shot good then another jam. This went on a few times...she figured it was the gun, so she switched out to the Beretta 92 I was shooting, which was bigger so the recoil was not quite as great. She didn't have any issues with it.

What happened was as the Sig was kicking back, it kicked so much that the slide was being prevented from going all the way back (due to being tilted back and hitting her wrist), therefore it wasn't charging the weapon properly and the next round jammed. So, it wasn't anything to do with the ammo or the gun itself, it was just that she couldn't handle the recoil.

Hopefully I explained that good enough that y'all understand what I'm talking about

Ok, so I'm wrong. I never said I was right. If I thought I was right I wouldn't have asked for insight. I wanted to know what you all thought. Thanks Thanatos

I don't think there is a size vs. reliability equation that will stand up. Other than most all 22 pistols are picky about what they like to shoot and even that wont stand up by brand of weapon or ammo.
The type of weapon will though. Any weapon built to really tight tolerances will have reliability issues. This is why target models make bad carry weapons. Tighter fit means less places doe dust, dirt to go and that will more often than not cause a problem. Combat weapons are built more loose and therefore can be more reliable.

So when looking for less FTF type issues it's much smarter to look at the type of weapon and what it was built for. Where caliber comes into play is more of a what you as the shooter are comfortable shooting. Or what you shoot best. Some don't like the snappy 40 round because..well..it's kind of a snappy recoil. It's a higher pressure round and it gets moving pretty quick. A 9mm is also higher pressure but not as snappy. The 45ACP is not a high pressure round and moves pretty slow in comparison and it's recoil is a good bit different than the 9mm or 40. I think the 357 Sig round was built more for better feed being it's bottle necked case. But is is a bit more to hold on to than any of the other three mentioned.

So find the caliber you like best. Then look for the model of weapon that will suit your needs. If you want it to work no matter what then you will be looking for a combat weapon. If you want to make raged holes at 50 yards then a target model is more up your alley. But that target model will not be able to push as many wounds through it in one outing than the combat model will. There's just more places for the crap to get into.

It's neither size nor platform... it's both. I'll break it down.

Size
If it were simply that smaller was better, try threading a needle someday with speed and repeatability. The size is just part of the problem. There's the little bugger of a problem that arises call GEOMETRY. Take something that has a small diameter but is long in comparison to that diameter, like a broomstick. Now, take the broomstick by the end (like the base of a bullet is pushed into the chamber) and try to poke that broomstick into a hole in the wall that is juuuuust a little bigger than the broomstick. If you have a steady arm and plenty of distance available between you and the wall to maneuver the broomstick, you shouldn't have a problem. If you shorten the distance available between you and the wall, you have more change for error.

Same thing goes for large diameters in comparison to their overall length. Once you try to move something long and skinny or fat and short, the geometry becomes more on an issue. 9mm is about in the middle, it feeds well in longer actions, shorter actions, pretty much anything (why did Glock have so much initial success with the 9mm still viewed as the pinacle of their pistols).

Platform
Sure, size matters, the radio reminds us all of that every day. On the other hand, the platform has a whole lot to do with the issue as well. Mainly on the length of the action. Longer action pistols have less worries as the rounds are stripped from the magazine at nearly parallel to the bore, whereas shorter action pistols have to get 4 monkeys and a girl with small hands to get a round into the chamber. The rounds come out of the magazines at such a steep angle that they have to have a lot of force behind them (recoil spring) in order to heave them into the chamber. So a big fat .45 round in a short action pistol (3") is going to have to do some serious geometric gymnastics to get those rounds into the chamber. That's why people who train defensive pistols don't recommend the 1911 pistol in anything but 5" for the most part. Sure, other can be made to work, but the 5" works best. Same goes for Kahr's. You wanna carry a Kahr, get it in 9mm, they got that one correct right out of the box. Their .45's seems to be too short to reliably feed with hard use.

I hope I didn't cause more confusion there, but it has more to do with geometry AND size than it does just size alone... ask your wife.

Originally Posted by RogerThat

Ok, so I'm wrong. I never said I was right. If I thought I was right I wouldn't have asked for insight. I wanted to know what you all thought. Thanks Thanatos

Quick, someone grab the tar and feathers!