June 10th, 2019

Tech Tip: Figuring Out Barrel Twist Rates

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

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.

After buying a new barrel, you should determine the true twist rate BEFORE you start load development. You don’t want to invest in a large supply of expensive bullets only to find that that won’t stabilize because your “8 twist” barrel is really a 1:8.5″. Sinclair International provides a simple procedure for determining the actual twist rate of your barrel.

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.

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.

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March 16th, 2012

Hickory Groundhog and Egg Shoot Slated for April 7, 2012

The Hickory Groundhog and Egg Shoot, the richest varmint shoot East of the Mississippi, is just three weeks away. The hugely popular Hickory Shoot will be held this year on Saturday, April 7, 2012. The basic entry fee is just $25.00 per gun. That’s cheap for a chance to win a bundle of cash, plus valuable prizes such as Shehane stocks and Nightforce optics.

Anatomy of a Hickory-Winning Rig — Brady’s Record-Setting 6BR
If you wonder what kind of rifle can win the big money at the Hickory Shoot, have a look at Terry Brady’s 42-lb 6BR. In 2010, Terry Brady won the Custom Class in the Hickory Shoot, setting an all-time record with a 99 score*. Terry was shooting a straight 6mmBR with 105gr Berger VLD bullets. His rifle looks “normal”, but it was actually purpose-built for Groundhog shoots, which have no weight limit in Custom Class. The fiberglass Shehane Tracker stock was stuffed with lead shot from stem to stern, so that the gun weighs nearly 42 pounds with optics. The Hickory winner, smithed by Mike Davis of Zionville, NC, featured a BAT DS action with a straight-contour, gain-twist Krieger barrel. The twist rate starts at 1:8.7″ and increases to 1:8.3″ at the muzzle. Terry was shooting a relatively moderate load of 30.5 grains Varget with Danzac-coated bullets. This load absolutely hammered, but Terry thinks the gun might shoot even better if the load was “hotted up a little.”

Terry Brady 6BR Hickory Groundhog Winner

Minimal Recoil and Insane Accuracy at 500 yards
In the picture above you see the Hickory winner fitted with a 5″-wide front plate. This was crafted from aluminum by Gordy Gritters, and Terry said “it only adds a few ounces” to the gun. Mike Davis installed threaded anchors in the fore-end so the plate can be removed for events where forearm width is restricted to 3″. The plate is symmetrical, adding 1″ extra width on either side of the Shehane Tracker stock. Gordy can also craft a 5″ plate that offsets the rifle to one side or the other. Terry hasn’t experimented with an offset front bag-rider, but he thinks it might work well with a heavier-recoiling caliber. Terry actually shot most of the Hickory match without the front plate so he could use his regular 3″-wide front bag. Even with the plate removed, Terry’s Hickory-winning 6BR barely moves on the bags during recoil, according to Terry: “You just pull the trigger and with a little push you’re right back on target.” With this gun, Terry, his son Chris, Chris’s girlfriend Jessica, and Terry’s friend Ben Yarborough nailed an egg at 500 yards four times in a row. That’s impressive accuracy.

*The Hickory employs “worst-edge” scoring, meaning if you cut a scoring line you get the next lower score. One of Terry’s shots was right on the edge of the white and another was centered right between white and black at 3 o’clock. Accordingly he only received 27 points for each of the 300 and 500-yard stages. Under “best-edge” scoring, Terry would have scored even higher.

CLICK HERE for 2012 Hickory Groundhog & Egg Shoot Info Sheet (PDF)

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January 20th, 2010

SHOT Show Report: The Boys from Bartlein

Bartlein BarrelsWisconsin’s Bartlein Barrels currently produces some of the most accurate cut-rifled rifle barrels in the world. We had a chance to chat with Bartlein barrel-makers Tracy Bartlein and Frank Green shortly after the doors opened at the 2010 SHOT Show in Las Vegas. Frank and Tracy weighed in on some of the “hot topics” in the barrel-making business: Gain Twist and the advantages of single-point cut rifling. In this interview, the “boys from Bartlein” discuss current trends in barrel-making, including what’s “hot” in short-range benchrest and the emergence of 7mm barrels for F-Class Open competition. Tracy also offers his opinions on cut rifling vs. button rifling, and he explains how modern technology has helped make modern barrels “better than ever”.

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December 12th, 2009

Krieger 6mm Gain Twists on Sale at Bruno Shooters Supply

Krieger barrelsBruno Shooters Supply is running a holiday sale on Krieger 6mm Gain Twist (GT) barrels. Short-range GT barrels cost $249.95 while long-range GT barrels are $269.00. Gain twist barrels have performed very well in recent short-range benchrest matches and long-range shooters have started to experiment with them in faster twists for the longer bullets.

Many Gain-Twist Options Offered
For short-range benchrest rigs, Heavy Varmint, Light Varmint, or Medium contour 6mm slow-twist GT barrels are offered in 15-14.2 twist, 14.6-13.8 twist, or 14.2-13.4 twist, all with a 27″ length, and a $249.95 price. For tactical, 600-yard, or long-range, Krieger 6mm GT barrels are offered in 8.75-8.3 twist rate for $269.00. Available contours are: #14, 15, 16 Palma; Heavy Varmint (1.250″ x .900″); and 1.250″ straight. Length is 31″ on the fast-twist 6mm barrels. Bruno’s also offers 29″-long, 1.450″ straight-diameter gain twist Krieger barrels for rail guns. These cost $315.00. For more info, visit Brunoshooters.com or call Bruno’s at (623) 587-7641.

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