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When I chamber a round in my XD Sub-40 I notice that it takes more time for the action to "catch the round" and slide it into the chamber than when it is empty. This is my first auto, is this common with all auto's?

Yes. The slide has to do work to strip off the round and chamber it.

make sure you lube your pistol good

CLP oil (lightoil) is fine..but an automatic works best with grease or heavy oil

Gun Butter a little dab will do ya!

Basic physics. The slide that has to strip a round from a magazine and seat it into the chamber, is going to be slower than one that encounters no resistance.

Something else to keep in mind...

This is going to occur much faster when it's loading from recoil than when you're loading a chamber by racking the slide (or releasing the slide lock). As others have mentioned, there's simply more work for the springs to do when chambering a round, so you're going to notice a little bit of slowing when compared to racking the slide empty.

Congrats on the XD you will love it. But be careful they have a habit of multiplying in your gun safe when your not looking.

Wouldn't it be safe to say that, as friction against the feed lips decreases due to decreasing spring tension on the magazine spring as the follower gets nearer and nearer to the top of the magazine, the amount of spring tension on the recoil spring required to strip the round also decreases, and consequently, the speed of the slide forward into battery increases marginally?

Don't forget... since this is your first auto ... when you chamber a round do it 1 of 2 ways:
1. Lock the slide back, put mag in & hit the slide release
2. Insert mag, grab back of slide pull it all the way back and LET GO

Do not follow the slide forward or 'ease' it forward. This may lead to improper feeding of rounds & generally not a good idea.

Good luck ... congrats on your purchase ... now get a Glock! j/k

The Annoyed Man wrote:Wouldn't it be safe to say that, as friction against the feed lips decreases due to decreasing spring tension on the magazine spring as the follower gets nearer and nearer to the top of the magazine, the amount of spring tension on the recoil spring required to strip the round also decreases, and consequently, the speed of the slide forward into battery increases marginally?

Yup.

flintknapper wrote:

The Annoyed Man wrote:Wouldn't it be safe to say that, as friction against the feed lips decreases due to decreasing spring tension on the magazine spring as the follower gets nearer and nearer to the top of the magazine, the amount of spring tension on the recoil spring required to strip the round also decreases, and consequently, the speed of the slide forward into battery increases marginally?

Yup.

And this is inversely proportional to the quality of the magazine. A magazine with better springs will hold the tension at a more constant rate than a magazine with a cheap spring. Also, the surface of the lips of the magazine play a key factor here as well. The smoother and slicker the surface of the magazine lips, the less resistance it offers when pushing a round forward. This means a magazine with very smooth lips will be more consistent in its feeding because there is less friction (and therefore less resistance to forward motion) created when the round is traveling forward against them. The better the surface, the less the magazine spring tension factors in.

Also something to note is the material the cases are made of. Steel and aluminum cases are going to offer up considerably more resistance to feeding than a brass case will. Even between manufacturers of brass-cased ammo, you'll find a difference. In my personal experience, Hornady seems to make the slickest brass I've tried, and I can certainly tell the difference in the smoothness of the action when I run it through my pistols.

NcongruNt wrote:

flintknapper wrote:

The Annoyed Man wrote:Wouldn't it be safe to say that, as friction against the feed lips decreases due to decreasing spring tension on the magazine spring as the follower gets nearer and nearer to the top of the magazine, the amount of spring tension on the recoil spring required to strip the round also decreases, and consequently, the speed of the slide forward into battery increases marginally?

Yup.

And this is inversely proportional to the quality of the magazine. A magazine with better springs will hold the tension at a more constant rate than a magazine with a cheap spring. Also, the surface of the lips of the magazine play a key factor here as well. The smoother and slicker the surface of the magazine lips, the less resistance it offers when pushing a round forward. This means a magazine with very smooth lips will be more consistent in its feeding because there is less friction (and therefore less resistance to forward motion) created when the round is traveling forward against them. The better the surface, the less the magazine spring tension factors in.

Also something to note is the material the cases are made of. Steel and aluminum cases are going to offer up considerably more resistance to feeding than a brass case will. Even between manufacturers of brass-cased ammo, you'll find a difference. In my personal experience, Hornady seems to make the slickest brass I've tried, and I can certainly tell the difference in the smoothness of the action when I run it through my pistols.

The long way of saying "Yup".

And this is inversely proportional to the quality of the magazine. A magazine with better springs will hold the tension at a more constant rate than a magazine with a cheap spring.

Not theoretically. An ideal spring, as it is compressed, always offers resistance to further compression in linear relation to the percentage of its length at rest that it has already been compressed. A 15-pound, 6-inch spring will offer 5 pounds when you compress it 2 inches and 10 pounds at 4 inches. Real springs aren't ideal, but pretty close, and this behavior cannot be modified. A "constant tension" spring is a myth.

Now, regardless, you can reduce, but not eliminate, the percentage change in tension by designing the system such that the spring is always under some tension; it is always partially compressed. Take that 6-inch spring and put it in a 4-inch magazine, and there will always be at least two pounds of force pressing a round against the magazine lips. That offers a far lower percentage change in tension than starting at an infinitesimal force.