March 25th, 2013

TECH TIP: How to Determine Your Barrel’s Actual Twist Rate

Sometimes you’ll get a barrel that doesn’t stabilize bullets the way you’d anticipate, based on the stated (or presumed) twist rate. A barrel might have 1:10″ stamped on the side but it is, in truth, a 1:10.5″ twist or even a 1:9.5″. Cut-rifled barrels, such as Kriegers and Bartleins, normally hold very true to the specified twist rate. With buttoned barrels, due to the nature of the rifling process, there’s a greater chance of a small variation in twist rate. And yes, factory barrels can be slightly out of spec as well.

Before you purchase a bunch of bullets and set off to develop loads it’s wise to determine the true twist rate of your new barrel. Sinclair International, in its Reloading Press Blog provides a simple procedure for determining the actual twist rate of your barrel. Read on to learn how….

How Twist Rate Affects Bullet Stability
Most of you know that the twist of the rifling in the barrel is what puts spin on the bullet. As a bullet is pushed down the barrel and compressed into the rifling, the bullet follows the path or twist of the rifling. The combination of velocity and bullet spin is what stabilizes the bullet. Finding the twist rate for your barrel will help you in selecting appropriate weight bullets for your firearm. Remember, the general rule is that the faster the twist rate for a given caliber, the longer the bullet (of that caliber) you will be able to stabilize. (Generally speaking, a longer bullet will also be a heavier bullet, but the bullet geometry dictates the needed twist rather than the weight per se.)

Determining Barrel Twist Rate Empirically
Twist rate is defined as the distance in inches of barrel that the rifling takes to make one complete revolution. An example would be a 1:10″ twist rate. A 1:10″ barrel has rifling that makes one complete revolution in 10 inches of barrel length. Rifle manufacturers usually publish twist rates for their standard rifle offerings and custom barrels are always ordered by caliber, contour, and twist rate. If you are having a custom barrel chambered you can ask the gunsmith to mark the barrel with the twist rate.

FirearmsID.com barrel rifling diagram
Erik Dahlberg illustration courtesy FireArmsID.com.

Sinclair’s Simple Twist Rate Measurement Method
If are unsure of the twist rate of the barrel, you can measure it yourself in a couple of minutes. You need a good cleaning rod with a rotating handle and a jag with a fairly tight fitting patch. Utilize a rod guide if you are accessing the barrel through the breech or a muzzle guide if you are going to come in from the muzzle end. Make sure the rod rotates freely in the handle under load. Start the patch into the barrel for a few inches and then stop. Put a piece of tape at the back of the rod by the handle (like a flag) or mark the rod in some way. Measure how much of the rod is still protruding from the rod guide. You can either measure from the rod guide or muzzle guide back to the flag or to a spot on the handle. Next, continue to push the rod in until the mark or tape flag has made one complete revolution. Re-measure the amount of rod that is left sticking out of the barrel. Use the same reference marks as you did on the first measurement. Next, subtract this measurement from the first measurement. This number is the twist rate. For example, if the rod has 24 inches remaining at the start and 16 inches remain after making one revolution, you have 8 inches of travel, thus a 1:8 twist barrel.

This rifling illustration was created by Danish graphic artist Erik Dahlberg. It is published here courtesy FireArmsID.com, an excellent website for forensic firearms examiners.

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March 25th, 2013

ATF Provides Answers to Top 10 Firearms Questions

Bureau of Alcohol, Tobacco, Firearms and Explosives ATF

The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), receives hundreds of telephone and electronic inquiries every day. In an effort to provide individuals with the most up-to-date information, ATF has compiled a list of the Top 10 Most Frequently Asked Questions. ATF has provided these questions, along with official ATF-sourced answers, in a 4-page PDF file you can download.

CLICK HERE to DOWNLOAD ATF Top 10 Questions and Answers PDF file.

The #1 most commonly asked question is whether a person barred by law from possessing a “firearm” can legally own a black-powder muzzle-loading gun. The answer to that question is quite lengthy, so we can’t include it here. But we have reprinted below the second, third, and fourth most-asked questions, along with the ATF answers. Download the PDF file to read the remaining questions and answers.

2. May I lawfully transfer a firearm to a friend who resides in a different State?
Under Federal law, an unlicensed individual is prohibited from transferring a firearm to an individual who does not reside in the State where the transferee resides. Generally, for a person to lawfully transfer a firearm to an unlicensed person who resides out of State, the firearm must be shipped to a Federal Firearms Licensee (FFL) within the recipient’s State of residence. He or she may then receive the firearm from the FFL upon completion of an ATF Form 4473 and a NICS background check. More information can be obtained on the ATF website at www.atf.gov and www.atf.gov/firearms/faq/unlicensed-persons.html. The GCA provides an exception from this prohibition for temporary loans or rentals of firearms for lawful sporting purposes. Thus, … a friend visiting you may borrow a firearm from you to go hunting. Another exception is provided for transfers of firearms to nonresidents to carry out a lawful bequest or acquisition by intestate succession. This exception would authorize the transfer of a firearm to a nonresident who inherits a firearm under the will of a decedent. See 18 U.S.C. 922(a)(5).

3. May I lawfully transfer a firearm to a resident of the same State in which I reside?
Any person may sell a firearm to an unlicensed resident of the State where he resides as long as he does not know or have reasonable cause to believe the person is prohibited from receiving or possessing firearms under Federal law. There may be State laws that regulate interstate firearm transactions. Any person considering acquiring a firearm should contact his or her State Attorney General’s Office to inquire about the laws and possible State or local restrictions. A list of State Attorney General contact numbers may be found at www.naag.org.

4. How do I register my firearm or remove my name from a firearms registration?
There is no Federal registration requirement for most conventional sporting firearms. Only those firearms subject to the National Firearms Act (NFA) (e.g., machineguns, short-barrel firearms, silencers, destructive devices, any other weapons) must be registered with ATF. For information on the registration and transfer provisions of the National Firearms Act, please refer to the ATF NFA Handbook at www.atf.gov/publications/firearms/nfa-handbook/ or contact the ATF NFA Branch at 304-616-4500. Firearms registration may be required by State or local law. Any person considering acquiring a firearm should contact his or her State Attorney General’s Office to inquire about the laws and possible State or local restrictions. A list of State Attorney General contact numbers may be found at www.naag.org.

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