Rifle Education Series Part 1: The Barrel

[samjoe]

I am starting a class for noobs and novices, as well as advanced users who want to learn something new, focusing simply on bolt action center fire hunting rifles. This could be a great way to understanding the overall firearm focusing on a few pages at a time dedicated solely to one part at a time.

I would like to use the "kiss" method since we are not publishing an article or textbook.

Please keep in mind that many people reading this will not have advanced knowledge of all terms used, so please define any terms that should require it.
Links are great and informative, but for our purposes, if you can post a short summary or bottom line information in lieu of, or accompanied with a link.

The format will be the anatomy of a rifle focusing on one mechanism at a time.

What is it?

What does it do?

Why does it do that?

Why do I want it to do that?

What happens if it doesn't do "that" properly?

What are the different types of designs and materials that are used in it?

What Its importance is in relationship to other mechanisms in the rifle?

What separates the higher performance from the lower performance parts?

And anything else important that I should know about that part.

 

[cbrgator]

I don't mean this disrespectfully, and I apologize if it comes off that way...

Should you really be teaching a class to a group of new-to-guns people if you can't already answer those questions yourself?

 

[franconialocal]

I think he is just trying to tap a great resource (THR) for any assistance with these topics...links and such. Some of us may have more experience in different areas of each topic that he's trying to cover (expert vs. "jack of all trades" type differences), military experience, police experience, hunters, smiths, etc.

OP...good luck with your project! I'm sure the newer shooters and THR members out there will really appreciate it!

Midway USA has a great firearm dictionary also that I'll link:

http://www.midwayusa.com/guntecdictionary.exe/

I'll speak from my own exposure here.....every once in a while I'll come across a term that I'm not familiar with and the GunTech Dictionary is a great place to get some clarification along the way.

 

[samjoe]

I'm not teaching the class, you are. If you have something to share. If it is incorrect, I am sure that it will be corrected by someone more knowledgeable.

Thanks for letting me clear that up.

 

[samjoe]

All I know right now is that the barrel is the metal cylinder that the bullet travels through when it exits the firearm. I think it travels through what is commonly known as the bore, and that bore has grooves that twist down it. these grooves are known as the rifling in the barrel (hence the name rifle) and they spin the bullet along its path. Supposedly this spin makes the bullet more stable in flight which increases accuracy and range.

What I don't know is why some grooves are small, some are large, and some are micro. what is the difference and why? The Muzzle is the very end of the barrel. What does it do and why is it so very very important not to damage it?

 

[samjoe]

Oh I forgot to ask. Does the bullet make contact with the whole diameter of the cylinder all the way down, or does it bounce around in there, or does it hardly touch at all surrounded by gases?

Do the grooves actually spin the bullet? or do they spin the gases which in turn spin the bullet?

 

[samjoe]

what is that area in the back of the barrel where the cartridge/bullet fits? what is important about it and its shape? I here alot about pressure. are the pressure specs of the rifle taken here or in the "receiver" (next topic) or both. what are the pressure specifications? are they important to the barrel?

 

[samjoe]

Why do some barrels have thicker walls than other barrels? What is the difference?

What is the difference between 2 barrels made the exact same way, but one is more accurate than the other?

 

[samjoe]

why do I want the bore of the Barrel to be "smooth and shiny!"

 

[USSR]

I would respectfully suggest you use the search function (and do a lot reading of past threads) to answer these very basic questions.

Don

 

[hub]

Here is a few good links. Some have good info on their websites and others may answer a few questions if you give them a call.

A good link to start with about barrel making.
http://www.rifleshootermag.com/gunsmithing/RSgunsmith1/

Microgroove INFO
http://www.leverguns.com/articles/fryxell/microgrove-barrels.htm

This Lilja page has some good info about barrel making, accuracy, etc.
http://www.riflebarrels.com/articles/barrel_making.htm

As does Shilen
http://www.shilen.com/faq.html

other good makers you could call or email.

http://www.hartbarrels.com/

http://www.pac-nor.com/

http://www.kriegerbarrels.com/Rapid...ommon/viewPage.cfm&PageId=2529&CompanyId=1246

http://www.douglasbarrels.net/

http://www.wilsonarms.com/contact_us.htm

 

[samjoe]

I will do the legwork because I need the educating. I will post the answers to my questions for anyone to add to or correct. I hope that it will benefit others out there that are curious to understand their rifle a bit more.

 

[Bobarino]

don't forget polygonal rifling as used in Glocks, HK's and Kahrs.

 

[scchokedaddy]

Hopefully members like Uncle Mike, Armed Bear, Dr Thad will chime in on this thread. Not to disrespect any other menbers,just these guys usually speak pretty clearly on issues and don't seem to mind unlike some others that just want to be sarcastic because they either allready know or think they do. Armed Bear no disrespect to you and others like you who offer a lot of knowledge for a lot of us, just to many for me to list these guys are just my favorites as they seem allways ready to jump in and help. samjoe I think its a great idea.

 

[samjoe]

First of all, accuracy isn't particular to the specific type of steel that a barrel is made from.
An extremely accurate barrel can be made of either a 4140-type chrome-moly or 416-type stainless steel.
The chrome-moly is less expensive to obtain, much easier to machine, and requires more care by the user to maintain.
The stainless is more expensive to obtain, more difficult to machine, and will have a longer accuracy life being more corrosion resistant than chrome-moly.

 

[samjoe]

Stress relieving the steel of a barrel is extremely critical in the manufacturing process of the barrel. Machining induces stress in parts. These stresses can cause distortions, cracks or bends in the barrel which must meet incredibly fine measurement specifications. Heat is used to break the molecular bonds in the steel (just like hot water breaks the bonds in your hair). Some manufacturers heat to a very high degree and cool slowly, while others cool it to near zero degrees and then heat it up. It is done to induce ductility (flexibility), soften the steel making it less brittle, relieve internal stresses, and refine the steel by making it homogeneous, which improves cold working properties.

Fluting (grooves cut on the outer part of the barrel) is done to lighten the barrel and expose more surface area of the barrel to speed the cooling process.

 

[samjoe]

Rifling is the process of making spiral grooves in the barrel of the firearm. It serves to spin to a projectile around its long axis. This spin gyroscopically stabilizes the projectile, improving its aerodynamic stability and accuracy.

Rifling is described by its twist rate, which indicates the distance the bullet must travel to complete one full revolution (ie. 1:10 in is 1 turn in 10" or 1:30 cm is one turn in 30 centimeters)

A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate. A combination of the weight, length and shape of a projectile determines the twist rate needed to stabilize it.

The larger and more spherical bullets require slower twist rates. The smaller and more elongated bullets require higher spin rates.

a gain twist or progressive twist is a twist rate that increases down the length of the barrel

 

[samjoe]

There are various ways to rifle a barrel.
The most common ways are
1. Cut Rifling (hook rifling) (single point cut rifling)
2. button rifling
3. hammer forging
4. broached rifling
5. flow forming

brief descriptions to follow.

 

[Art Eatman]

Re post #17: It's less an issue of relative diameter than it is the ratio of length to diameter.

A round ball doesn't need to be spun as fast for stability; the ratio is 1:1. The longer the projectile with respect to its diameter, the faster the necessary rate of twist.

 

[samjoe]

The grooves are the spaces that are cut out, and the resulting ridges are called lands.

Most rifles have a minute gain twist if not a higher one due to the fact that a decreasing twist down the length of the barrel is detrimental to the accuracy of the projectile.

 

[samjoe]

Thanks Art

 

[samjoe]

Hammer Forge Rifling is a process used by most large manufacturers like Remington, Winchester, Ruger, Sako and Steyr. It involves very large and expensive machinery that can take a nearly 2-inch-diameter bar of steel about 12 inches long with a hole through its center, and by hammering it, elongate it into a 24-inch-long tube having a muzzle diameter less than one-third of what it was originally. it is suited more for mass production. It requires little man labor hours, and it is a fast method.

 

[samjoe]

Button Rifling is using a highly-polished carbide "button," about half an inch long, tapered at both ends and containing the rifling in reverse, is silver-soldered to the end of a smaller diameter rod and pulled through the bore. The grooves are literally pressed or "ironed" into the steel. It must be done when the barrel is in the blank state, i.e., a straight cylinder, so that its resistance to the button passing through it is uniform the entire length. This method is most commonly used by specialty companies. Savage is one of the larger manufacturers to use this method. It is relatively fast and the equipment is less expensive than hammer forging equipment.

 

[samjoe]

Cut Rifling is the process of cutting one groove at a time down the bore of the barrel using machining equipment. The major advantage of cutting the grooves rather than hammering or ironing them into the bore is that there is no stress introduced. Special twist rates and groove depths present no more of a problem than standard specs. One can truly have a "custom" barrel using this method. It is time consuming and takes up more labor hours than other methods. One barrel with proper equipment will take 2 hours or more.

 

[samjoe]

broached rifling is the process of cutting all grooves at one time with a special progressive bit almost like a tap that threads a hole for a screw. Broaches are very expensive-too much so for the independent barrel makers. Mostly governments use them in war-time production facilities. Many Mil-surps will have broached rifled barrels