What are the 4 basic components of ammunition
There are 4 components that make up all rifle cartridges. The bullet (1), the case (2), gun powder (3) and the primer (5). (4) in the illustration below is the rim of the case which is used by the ejector to remove the spent cartridge from the firearm. The primer is the component that ignites the powder inside the bullet casing when struck by the firing pin of the firearm causing the bullet to fire. This cartridge is called a center fire.
There are minor variations to this in existence. The cartridge you see above has what is called a boxer primer. Some older cartridges are equipped with Berdan primers which is similar to the drawing above but has two openings between the primer pocket (5) and the powder (3). Cases with Berdan primers should not be reloaded.
The drawing below shows the difference between rim fire and center fire cartridges. In rim fire the location of the primer is inside the case and dispersed around the rim of the cartridge but both are made up of the same 4 basic components.
Because of this it is not feasible to reload rimfire cartridges.
What is the difference between rim fire and center fire ammunition?
There are two basic types of rifle and pistol cartridges. Center fire and rim fire. The biggest difference between rim fire and center fire cartridges is where the primer is located.
Center fire cartridges have the primer located in the center of the base of the case. When the rifle firing pin strikes the center of the primer it ignites the powder.
A rim fire cartridge has no opening in the base of the case. Primer compound is inside the case and dispersed around the edges of the base which is where the firing pin strikes the case. See the illustration below.
Above is a great graphic created by Long Island Firearms that shows the difference between rim fire and center fire. The cartridge on the left is a rim fire. The center fire cartridge is on the right.
For a center fire round that has been shot but the primer hasn't been removed you would see a small dent in the center of the primer.
The center fire cartridge pictured below on the left has not yet been shot as no dent is present in the primer. Center fire technology is used in both rifles and pistols. The cartridge on the left is a 9mm pistol cartridge, the one on the right is a 223 rifle cartridge. The primer has been removed from the 223 cartridge to show the flash pocket and the opening between the primer and the gun poweder inside the case.
The second type of cartridge is a rim fire. See the photo below. There is no opening on the bottom of the case. Primer compound is inserted into the case during manufacture and dispersed around the edges of the rim on the bottom of the case. The firing pin on a rim fire firearm strikes and dents the edge of the rim to ignite the primer which ignites the powder. The case on the left has not been fired while the one on the right has.
Rim fire cartridges are smaller than the typical center fire. The reason for that is because the smaller rounds generate less pressure when fired, the case doesn't have to be as strong to funtion correctly.
Rim fire started first and center fire came along later. Center fire technology allowed more powerful rounds. Since rimfires still worked well with that technology there was no reason to upgrade cartridge type.
At the time there were thousands, and still are thousands of firearms out there that were designed to shoot rim fire ammo. Why change it if it works?
Also, costs have been kept lower by keeping the cartridge in rim fire. At this writing a 22 cartridge can be purchased for 4 to 6 cents each vs over a dollar per round for my Remington 25-06.
What are the pros and cons of rim fire
One of the largest benefits of rim fire ammunition is the low cost. At this writing, bulk 22 ammo can be purchased for 4 - 5 cents per round. 17 hmr is around 20 cents and 17wsm is in the 25 - 30 cents / round. Compare that to 6.5 creedmoor which is from 85 cents to well over $2.00 for top quality and it is easy to see the cost benefit of rim fire.
This is one reason why PRS competitors use rim fire ammo in rifles that are similar to those they use in competition but shoot rim fire ammo. This are called trainer rifles. Recoil is not the same but shooting techniques for accuracy are the same.
The low recoil of rimfire ammo makes it perfect for accurate shooting, especially with match grade ammo. It is a great way to get new shooters started in the sport. Many pros revert back to rim fire ammo for practice when bad habits like flinching or jerking the trigger start to creep back into their technique. I have also used this trick to eliminate bad habits and it works.
For the regular Joe like you and I, which would you rather do on a trip to the range? Shoot 10 rounds of 6.5 creedmoor and go home, or over 400 22 rounds? I thought so.
The hobby of long range rim fire is cheaper from every standpoint. I built a highly competitive 17 hmr for under $500. That amount probably wouldn't buy a workable scope for large caliber long range shooting. The entire hobby of long range rim fire is cheaper when purchasing ammo, rifle components, and accessories than large caliber.
Because our definition of long range is around 500 yards and not 1000 to 1500 yards, it is much easier to find a good place to shoot.
Rim fire ammunition is typically dirty and requires more attention to cleaning your firearm to keep it functioning and shooting at it's best. For me, this is a small price to pay to be able to get it so cheap. I would suggest cleaning every 400-500 rounds or so. Much beyond that and you start to lose a little accuracy.
Rim fire ammo is also know to be more inconsistent or less reliable than center fire. My experience has found this to be true but mostly in the cheaper bulk variety. I have seen very few feed or misfire issues with mid to high quality rim fire ammo.
Rim fire ammo is limited to small calibers because of how "fragile" the cases are. In this sense, fragile is defined as unable to withstand the pressures generated by big bore calibers and primarily because of this can't be reloaded practically.
There are some kits available now that supposedly allow you to reload rim fire ammo. I have never tried this product but I have read articles on how it is done. I won't go into the detail here but I learned from these articles that reloading rim fire ammo is not for me. It is very time consuming because it is all done by hand. There is a danger when mixing the primer compound of explosion. With the low cost of rim fire ammo now, to me it is just not worth the headache.
Because this design is limited to smaller calibers, bullet flight is much more susceptible to outside elements, the largest being wind. If the cartridge is being used for training for larger calibers, this could be a good thing. More is learned at shorter distances. It has been said, shooting a 22 at 300 yards is like shooting a larger caliber at 1000 yards with the variables that come into play.
All rim fire ammunition tends to run dirtier than center fire. This is primarily because of the powder used that will still yield consistency in the rim fire but allow cost to remain low. These rifles take a little more effort to cleaning them properly but the low cost more than offsets that issue in my mind.
For the average Joe who likes to shoot, and shoot a lot like me, rim fire makes a lot of sense. It's cheaper and you can shoot much more. Finding a place to shoot is also much easier because the hobby requires less land or distance to enjoy. Working with these little rifles to convert them into tack drivers are a ton of fun and inexpensive in comparison to larger calibers and almost everyone can afford to enjoy the sport. I can honestly say that my shooting ability has improved tremendously since realizing these facts and starting to shoot more rim fire rifles.. Don't get me wrong, I still have my big guns and always will, but when I have the shooting urge and want to have some fun, I grab the rim fires. Give it a try and I am sure you will love it.