Are they packed completely like air-tight full inside?  Or is there a little open air?  I'm wondering if some brands have more or less than others for the same caliber.

Since we're in the handgun forum...  I've never seen a compressed load for a pistol cartridge, however I'm far from an experienced reloader.  Not saying they don't exist, I've just never heard or seen one.

I have seen and loaded compressed loads for rifle rounds.  It's been years but I believe Varget has a compressed .223 load that I'd use for a Rem 700.

To answer your question, it will vary depending on the type of powder used and the type of projectile.  The 2 loads I use for 9mm using Titegroup powder is 4.8gr of powder for a 115gr round nose or 5.0gr of powder for a 147gr round nose bullet.  For .223, I used AA2230 powder and it was 25.0gr for a 55gr FMJ bullet.

It depends on the burn rate and the fill density of the powder.

Some medium to slow burning powders with low fill density can completely fill the case. Unique in 9mm loads for example, are sometimes compressed.

On the other side you have things like red dot or bullseye that don't take much and those are likely not even 50% filled.

Then you have powder puff loads for things like 38spl and 357 (for instance, a mild 38spl load in a 357 case), that use under a quarter of case capacity.

It all just depends.

No gunpowder in any of the bullets. That would be illegal to make exploding bullets. It can be done, but you don't want to do it. Cartridges have "gunpowder"  Although "gunpowder" to some people means black powder.

Modern ammunition is loaded with a propellant called  smokeless powder. But that is a nitpick, and you can call it gunpowder if you want. There are thousands of different powders, historic and current. These charges of powder are carefully weighed, and carefully chosen for each load. They are loaded into the cartridge case, usually from a carefully adjusted metering powder measure. The correct sized and type of primer is inserted into the cartridge case before this charge of powder is metered and dumped into the case. Then the bullet is seated to the correct depth in the case, and usually done but not always done in a different step the bullet receives the correct type of crimp into the case. Usually a different type of crimp for revolvers vs. auto pistols and/or rifle cartridges.

Terms:  Cartridge or "round of ammunition" is the complete package of primer, cartridge case or "brass", propellant also called "powder" and projectile, also called "bullet"

Primer types are rifle and pistol and shotgun types.  Primer sizes are small and large and size 209 for shotgun.
Propellants number into the thousands, but there are three basic types. Rifle, Pistol and Shotgun, but some can be used interchangeable, like pistol and shotgun, but you must follow the recipe's.
Bullets are usually made for either rifles or handguns, but there are thousands of different sizes and types. Again you follow the precise recipe's.

So your question does NOT have a simple answer. The science of ballistics is complicated, both internal ballistics (inside the cartridge) and external ballistics when the bullet leaves the barrel.

Ummmmmm. Powder doesn’t go in bullets. Is goes in the case. But you do you boo,boo

Join date and post count noted.    

Incorrect.  There are advantages of a compressed load.

Here is what Hodgdon says about compressed loads;

COMPRESSED LOADS
Normally a pistol or rifle shellcase is considered full, or 100% loading density, when the powder charge sits at the base of the bullet when the bullet is fully seated. It is possible with some powders and cartridges to increase the powder charge slightly above this point, such that when the bullet is seated it actually compresses the powder charge slightly. This condition is known as a compressed load.

Hodgdon notes in its reloading data if the subject charge is a compressed load. A full case, or lightly compressed charge is an ideal condition for creating loads with the most uniform velocities and pressures, and oftentimes, producing top accuracy.

https://www.hodgdonreloading.com/compressed-loads

Precisely.

I think that line of thought just stems from people either not being reloaders themselves, or not being familiar enough with all the cartridges that may make use of compressed loads.

Obviously not all combinations of projectile/cartridge/powder are safely compressed, and so if you don't dabble enough to know that such combinations exist, I can see how one could THINK it could be a "no no" even though many loads are compressed...some very much so.

You can usually shake a round and hear the powder moving around inside.

Never leave air space if loading black powder. Other than that, it is more forgiving.  
I’ve loaded compressed in rifle brass many times.

go to nato reloading . com.
They tested plenty of 9mm compressed loads.

Not much disagreement with the replies here.

Note that black powder is very bulky and many old design calibers that were originally loaded with black powder have quite a bit of empty space in the cartridge when loaded with modern smokeless powder. Two examples that come to mind are 45 Colt and 45/70 .

Ummm....   The correct answer to the OP's question is:  NONE

If the OP wants help, he really should pick up on how boomers learned...
Pick up a damn book on reloading.
Sitting around a watering hole to get info is a poor learning source.

Not really.  He got his answers, right? He wouldn't even have to weed through crap if people didn't post nonsense.

Amiright?

Also, you've never asked a question here to get help, EVER?

Then why are you in tech, if not to help, or not to ask questions?

Simple answer is that it depends on the load.  For instance I have some 125gr 357 Mag and 110gr 357 Mag, both from Remington.  You can shake the 110gr and feel the powder moving around, it's not loaded as hot.  You can't hear the powder move around in the 125gr, which means it's loaded hotter, which it is because it's both heavier and faster.  Most high volume range ammo uses relatively little powder, fast burning powder uses less powder where slower burning powder, for more powerful loads, requires more powder and takes up more space inside the cartridge.

Marty Ter Weem of Teppu Jutsu said when they first started load development on the .458 socom they’d just put at much Reloader 7 in the case as they could with any given bullet and fire it, then measure the velocity and look for pressure signs.

Great posts.  What started as a simple stupid question is actually pretty interesting.

Next question.  

What about magnums & +Ps?  What is it that makes 'em magnum or +P?  More gun power or something else?

I have a few different kind of rounds can't hear anything if I shake 'em close to my ear.

Some places to start:

https://www.returnofkings.com/116344/an-introduction-to-rifle-and-pistol-ammunition

https://www.pewpewtactical.com/beginners-guide-to-reloading-ammo/

Also, if you have the Amazon Kindle app, there are decent books there on the subject of cartridges, ammunition, reloading, etc.
You can sometimes learn a decent amount just from downloading a free sample of a book (nearly every book offers a free sample) and if you have Kindle Unlimited, there are a decent number of "freebies" you can add to your library.  Or just buy the book, it's cheaper than print.

This is an outrageously newb question.  I'm gonna take it that you somehow found your way in here from other part of the internet.

I'm going to post a pic to help people explain.  Yes there is some air in the cartridge.  If it was so stuffed that would be dangerous.  



Note the bullet is the front of the cartridge.  It is the part that comes out of the barrel.  The powder is in the case, behind the bullet.  People that know next to nothing about guns often call the whole thing a "bullet" but that is very confusing and makes explaining it to you very difficult.

"+P" cartridges have a bit more powder which increases the velocity of the bullet.  But they are still not completely stuffed. A +P cartridge is a slightly more powerful version of a common cartridge that can be fired in (most) guns that take that cartridge.   "Magnum" usually denotes a completely different type of cartridge.

Some of the +p stuff comes about because of old cartridges and modern firearms.  For example early .257 Roberts rifles were based on the 7mm mauser German round from ww1 and earlier.  Many old 7mm mausers were rebarreled and chambered in the .257 Roberts cartridge.  By today's standards the 7mm mauser rifles of the day were not strong actions, a modern built rifle is capable of much higher pressures and correspondingly higher performance - but you can't sell ammo for a .257 Roberts that is going to blow up or damage grampas old 7mm conversion.  SAAMI standards for the .257 Roberts are downrated accordingly. So lets make a higher performance ammo for the modern rifles and we'll call it a .257 Roberts +P.

I hope those loads are typos.  The 115gr might be OK, definitely hot, but if you are loading 5.0gr of Titegroup with a 147gr bullet I hope you have good insurance; both health and life.

There is no need for air space in a loaded cartridge.  Think of the primer like a match. -. when hit by the firing pin, the primer ignites a small amount of a chemical which heats the gun powder enough to release oxygen sufficient to burn the powder.
The extra oxygen was attached through processing the gun powder components with nitric acid.
Just a little trivia for the OP, although vastly simplified.

Ed for correct acid.

Ok some good info in this thread, some not so good.  In a handgun how much powder is in the case depends on the burn rate of powder you choose to use. An analogy would be gasoline burn speed vs diesel. Put a match to a puddle of gas and you may lose eyebrows, same match to diesel and it just burns. Same with ‘fast’ powders vs ‘slow’ powders.

A fast powder burns quickly and builds pressure fast so you only need a relatively small quantity to reach proper operating pressures for a cartridge, a slow powder burns slowly and builds pressure slowly so you need more for the same cartridge to reach the same operating pressure. I’ve used a fast powder (bullseye or clays) in .45acp and had so much air space I could’ve easily double or triple charged without overflowing the case. I’ve also use a slow powder (blue dot) and had almost zero airspace under the seated bullet. Same thing but more so with a .44 mag.

A safe charge of Unique (medium burn rate) had ‘maybe’ half the case full. A safe charge of N110 (a slow pistol powder) was genuinely compressed. And showed zero pressure signs for many thousands of rounds.

The risk of double charging is VERY real with fast powders which is a real concern for reloaders. Plus due to the small quantities used, even a small delta in powder charge can take you into risky territory.

May I ask what prompted your question? We may be able to tailor our answers better if we know what’s behind it.

It was only a general curiosity.  Thanks.