Bartlein T-Rifled Barrels
© 2017 by Glenn Burroughs
Some months ago a nice custom rifle barrel chambered in 6mm BR Norma and threaded for a Remington 700 action came into my life. It originally belonged to a friend who shot it less than a hundred times, then decided he wanted a barrel with a faster twist for those very accurate, long range 105-grain bullets. The 6mm BR is just about my favorite cartridge so this barrel would be the basis of a new, and hopefully inexpensive, varmint rifle. The barrel was already threaded and chambered so the cost to fit it to an action shouldn’t be too high. All that was needed would be to locate an old Remington 700 action and stock.
Eddie Webster, a gunsmith noted for his accurate rifles, was contacted to discuss the idea of using the barrel to create a nice varmint rifle… one that would be easy-on-the-pocketbook. His quick response changed everything: “That sounds like a good idea, but if you are going to build a rifle why don’t you spend a little more money and build a really nice one. That way you can get exactly what you want… like a barrel with a 1:8-inch twist. Take a look at Bartlein Barrels, the ones they make with transitional rifling, that might kindle your interest. And look at the H-S Precision stocks, they shoot well even without bedding. And if you do decide to bed, then skim bedding would do just fine.”
His comments got me thinking. Sitting in the gun safe was a new Remington 700 single shot action that has been idle for several years. This would be the perfect start for a really nice, long range varmint rifle. Also resting in the safe was a Nightforce NXS 5.5-22x50 scope that needed to be put back in the field. With these two items in hand the plan for an inexpensive rifle was dropped… I decided to sell the used 6mm barrel and have Eddie put together a nice rifle.
Eddie’s suggestion for a barrel with transitional rifling caught me off guard… I wasn’t sure exactly what today’s version of transitional rifling was. It’s common knowledge that transitional twist rifling starts with a slower twist at the chamber and the twist rate increases towards the muzzle. Also that it was a technique used in the old black powder rifles… but how is it being used today? And is it really more accurate? The internet search for information began and after a few hours the result was two schools of thought, one that transitional twist barrels are no better than standard twist, and the other was they are the best thing since sliced bread. And both groups had their reasons. No place could be found that offered scientific proof as to why one was better than the other. But I did find a site with sufficient information to make me want one and, like Eddie Webster recommended, a Bartlein in particular. It was The Precision Rifle Series site.
The Precision Rifle Series (PRS) is a group that monitors the individuals competing in the most recognized and reputable long range rifle matches in the nation. There is a website that reports on the activities of the PRS known as the ‘Precision Rifle Blog’, and they had an article titled, “Precision Rifle Barrels - What The Pros Use”. Following is a quote from the article:
“Bartlein Barrels leads the pack again for the 4th year in a row! Almost half of the shooters in the top 100 were running Bartlein barrels. Bartlein uses some of the most advanced computer-aided manufacturing processes available.”
A chart included with the story showed, of the eleven barrel makers listed, Bartlein provided 43% of the barrels. Quite a remarkable statistic. The report did not designate the type of twist for the barrels but Bartlein produces a lot of transitional twist barrels.
The information gathered about Bartlein barrels was impressive, so I visited their website where they commented about the accuracy of their barrels: “The uniformity in our barrels and finish of the bores is second to none. Our rifling machines are so accurate, we can carry the twist rate to the 4th decimal point (example: 11.3642). The process of Single Point Cut Rifling is the most stress free way to rifle a barrel. The twist is exact, where as other forms of rifling can have variances due to the process they use. Also, the bore and groove dimensions are more uniform.” I have favored cut-rifles barrels for years, but never considered the accuracy of the machine that was cutting the barrel.
But the icing on the cake was to learn the guru of 100-yard benchrest shooting, Tony Boyer, was using Bartlein transitional-twist barrels. According to articles Tony’s barrels only have a slight gain in the twist, something like 1:15-inch at the breech and 1:14.25-inch at the muzzle. But the bottom line is that many of the best and most accurate shooters in the game are using, and winning with transitional twist barrels. That was good enough for me. I decided to contact someone at Bartlein Barrels.
The phone was answered by Frank Green, one of the founders of Bartlein Barrels. After a few introductory comments I asked Frank what advantage a transitional-twist barrel has over a standard twist. He commented, “It’s hard to prove that a t-style barrel is more accurate than a standard twist, too many factors involved, barrel quality, shooter, ammo, and so forth. Some say the pressure build up is not as bad, we hope to confirm this in the near future. We sent Hornady several barrels for proof testing, they have the equipment to make the necessary measurements. Maybe we will know something in a few months. Some say the barrels last a little longer because the bullet starts off a little faster. Each shooter has an opinion. Looking at match results the t-twist barrels are being used by the top shooters and setting records. That is pretty strong evidence.” When Frank said the top shooters were using transitional barrels I asked if Tony Boyer used Bartlein barrels. Frank replied, “We have been providing barrels to Tony since 2007.”
I continued, “Besides the transitional twist feature, what else can you tell me about Bartlein barrels?” Frank replied, “We use cut rifling because it’s better than using a button. A cut barrel, even with a straight twist, is more uniform and consistent than a button barrel. With button riﬂing, the button can hit a hard or soft spot in the steel, and it will slow the button down. The button could speed back up and complete its twist, but either way you end up with a non-uniform twist. This and a twist that keeps getting slower towards the muzzle are accuracy killers and consistently lead to problems such as ﬂiers. Even a slight gain in twist will help accuracy and not hurt a jacketed bullet.”
After our conversation I decided to order a 6mm barrel for 105-grain bullets and asked what twist would be best in a t-twist barrel? Frank replied; “There is really no hard rule as to what gain twist to go with. The only rule I go with is the ending twist has to be fast enough to stabilize the bullet you intend to shoot. So in this case I would end the twist at least at 8. If you wanted a suggestion I would go with an 8.2 to a 7.7 twist.” When I asked why he picked that particular twist he quickly replied, “Because it works.” He continued, “Why such a minimal gain? We've done them where they go from a 13 to a 6.5, like in a .375 caliber. So we've done radical gain-twist barrels, but again there are no hard and fast rules for what gain-twist to use, and offhand I don't see a radical gain offering anything extra. All of the 20mm and 30mm cannon barrels on our fighter planes are gain twist. Makes sense on the bigger stuff… with a 20mm you’re starting a bullet that is three quarters of a pound in weight. My only thought is it might help with the torque of the gun. One guy we make AR barrels for is getting his 13-6.5 twist for shooting the 90-grain bullets. He is trying to get all the velocity he can out of the AR match rifle and also fight the bullet failure rate on the 90's, which is high. He's been very happy with them!” After a most enjoyable discussion with Frank Green my order was placed based on his recommendation, to be shipped to Eddie Webster in Boones Mill, Virginia.
With the barrel on order the rest of the rifle components needed to be determined. With Eddie Webster’s help one of HS-Precision’s Pro-Series Competition Stocks was selected, a PSC023. This model fits a Remington 700 short action ADL with a bull barrel. The color chosen was a black base with red spatter. Next was a replacement firing pin assembly. For some reason some of the Remington 700 bolts have a heavy firing pin spring that is too long and poorly fitted. This can cause trigger resistance, bolt closing effort, and increased lock time. Based on the recommendation of several gunsmiths I ordered a Pacific Tool and Gauge complete assembly with an aluminum shroud for less than $50. It provides a faster lock time, better fit and better sear engagement. When the stock and firing pin assembly arrived the Nightforce scope and mounts were gathered and the items delivered to Eddie.
Once the rifle was under construction it was time to prepare the brass. First the necks on the Lapua brass were turned just enough to knock off the high spots. Then the cases were trimmed… the RCBS 3-Way cutter attachment was installed on the RCBS Trim Pro-2 case trimmer. This device not only trims the case but chamfers and de-burrs the case at the same time, speeding up the process considerably. It also provides precise processing of cases, something not likely when doing it by hand with a chamfering and de-burr tool. In short time the cases were all trimmed to length, chamfered and de-burred. The flash holes were checked… each had been cleanly punched out. Just to be sure, they were touched up lightly with a flash hole de-burring tool. Each case was weighed, with the result showing a variation of less than two grains… no sorting was necessary. The brass was ready.
A set of RCBS Gold Medal dies were selected for producing the ammo. The 0.265-inch bushing for the sizing die was determined based on the neck diameter of a loaded round, minus 0.002-inch. This would size the neck sufficiently to insure a snug bullet fit, and prevent the bullet from slipping into the case while being ‘jammed’ into the lands during the seating operation. The RCBS micrometer seating die was adjusted to seat the 105-grain bullets exactly 0.007-inch into the lands. Test ammo was loaded and set aside, awaiting the return of the rifle... and it was not long before the rifle was in my possession.
When I first took the rifle to the range all of the rounds had been loaded with a standard 6mm BR recipe, 30.0 grains of RL-15 powder with a 105-grain bullet jammed 0.007-inch into the lands. This load had performed very well in many rifles so I was pretty confident it could easily end up being the best load for the new rifle. But that was not to be. There were some good 100-yard groups, but there were also several measuring over an inch. I was somewhat bewildered. After considerable time punishing myself mentally for only loading one combination of powder and bullet I decided to switch the powder to Varget and test four different brand bullets. The next batch were loaded with 30.0 grains of Varget, and the bullets used were 105-grain Berger, 105 grain Hornady A-Max, 105 grain Lapua Scenar and 105 grain Hornady Match… all jammed 0.007-inch. The results were pleasing to say the least; the Berger group measured 0.375-inch, the A-Max was 0.386-inch, the Lapua was 0.517-inch and the Hornady Match came in at 0.459-inch. This was more like what was expected. It looks like the selection of a Bartlein barrel was a good choice, although partial credit is due to the other quality components.
While I was measuring the group sizes I thought things were looking pretty good, especially considering this was in the early stage of load development. And to be realistic I had to factor in the fact that my eyesight is not the best. Someday I will get one of the younger shooters at the range to shoot some groups with the rifle. Then I will find out how well the rifle really shoots.
(Neither the writer nor the publication accepts any responsibility for the safety of loads mentioned herein in other firearms. They were safe in the firearms mentioned and on the day of their firing. Start low with your loads and work slowly up.)
Bartlein Barrels, Inc.
W208N16939 N Center Street
Jackson, Wisconsin 53037
Eddie Webster (gunsmith)
W&M Gun Repair
3607 Alean Road
Boones Mill, VA 24065
Phone: (540) 420-0795
Graf & Sons, Inc. (Lapua Products)
4050 South Clark
Mexico, MO 65265
Phone: (800) 531-2666
1301 Turbine Drive
Rapid City, SD 57703
Phone: (605) 341-3006
Pacific Tool & Gauge, Inc.
598 Avenue C
White City, OR 97503-1031
605 Oro Dam Blvd East
Oroville, CA 95965
About The Author:
Glenn Burroughs is a retired computer systems manager with a lifelong love of guns. His main areas of interest are accurate rifles, wildcat cartridges, reloading and bench shooting. He also enjoys an occasional trip out west to the prairie dog country. Glenn was a columnist for Precision Shooting magazine and also wrote articles for Varmint Hunter magazine. He resides in Lynchburg, Virginia.