May 8th, 2016

Sunnen Barrel Honing System Used by Pac-Nor Barreling

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel
Pac-Nor Production Manager Casey Dichter says the Sunnen hone produces a consistency in bore diameter that is much superior to hand-lapping. The Sunnen machine has all but eliminated the standard pre-rifling lap. “You can really tell the difference between a bore that was honed before rifling and one that was [only] lapped”, notes Dichter.

Gun Barrel Honing System Hits Target for Pac-Nor Barreling
Manufacturing precision rifle barrels has always been something of an art that involves hand lapping of the bore surface twice, before and after the rifling profile is cut or swaged in by a rifling button. In fact, a bright, hand-lapped bore is considered one of the hallmarks of a precision rifle barrel, despite the inherent variations from manual work done by people who get bored and tired from the monotonous chore. Pac-Nor Barreling, Inc. set its sights on this issue more than a year ago and hit the X-ring with the newly developed Sunnen HTE honing machine. The machine has all but eliminated Pac-Nor’s pre-rifling lap, which is the more difficult and time-consuming of the two laps. Pac-Nor is also producing as many custom barrels as ever, but with a slightly smaller staff. “Our objectives with the hone were to build a better product with less labor, and the honing machine has exceeded my expectations,” said Pac-Nor Production Manager Casey Dichter. “The hone produces a consistency in bore diameter that is head and shoulders above lapping, within two to three millionths of an inch end-to-end when it’s really dialed in,” he said. “This, in turn, improves the consistency of the rifling process by minimizing variation in the depth of the grooves. We still finish lap after rifling, but it’s easier because we just polish off the fine crosshatch finish that may be left after honing and rifling.”

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel
The Sunnen hone secures the barrel blank in a 3-jaw chuck, with honing oil pumped into one end while the tool works from the opposite end. Sunnen’s specialized Long Bore Tool uses metal-bond diamond or CBN superabrasives to quickly remove reamer marks, waviness, tight spots and other imperfections left by upstream processes.

Honing is an ideal replacement for hand lapping barrel blanks before rifling. It quickly removes reamer scratches and surface waviness without labor-intensive hand lapping. A typical 600-grit abrasive can produce a 6-10 microinch Ra (0.15 to 0.25 µm) finish in a reamed barrel blank. By producing a consistent bore diameter (±0.0001″ or less), parallelism, roundness and surface finish end to end, honing yields more consistent performance from rifling buttons and cutters, resulting in a constant groove depth. The ideal bore geometry reduces distortion of the bullet shape.

Pac-Nor’s barrel-making process starts with cutting and facing premium bar stock, followed by gun drilling, done by four Pratt & Whitney twin-spindle machines and an Eldorado CNC twin spindle. After reaming, the barrels are gauged for size. Depending on the condition of the reamer, 0.0004″ to 0.0007″ of material is left in the bore. This must be manually lapped out or honed out to final size for rifling. “Everyone who works here has done hand-lapping,” said Dichter. “It’s an unpleasant job, particularly if the reamer is starting to get dull. Lapping may take 10 to 45 minutes, depending on the caliber of the barrel. We tried to shorten this, but when chatter marks get ‘ironed’ into the surface by the rifling button, the finish lap is even longer and more difficult, so there is no advantage. With lapping, too, there is potential for variation, simply because it’s a manual process. Lapping can also be a production limiter and in our region we have a very small labor force to draw on when we want to grow.”

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel
Pac-Nor cuts and faces premium bar stock, then gun drills on one of five twin-spindle machines, followed by reaming of the blanks. This rack of barrel blanks awaits completion.

The company had explored honing in the nineties, but re-visited the idea when Sunnen introduced its HTE honing machine in 2014. The HTE is a horizontal machine that can hone small-bore rifle barrels, with a diameter range of 0.150″ to 0.790” (4-20 mm), and lengths up to 60″ (1,524 mm). Designed specifically for long small bores, the machine features an extremely sensitive drive and tool feed system that provide maximum protection against tool overload/breakage. Tool specific force limits and run settings are stored in the touch-screen PC control, allowing the system to sense tight sections in the bore and correct them automatically.

Sunnen also developed a new Long-Bore Tool (LBT) designed to take on industry’s most difficult honing challenges in small bores of .17 caliber rifle barrels. The tool quickly remove reamer marks, waviness, tight spots and other imperfections left by upstream processes. The LBT utilizes metal-bond diamond or CBN super-abrasives for high productivity, long life and fast cycle times. Precision-machined of through-hardened tool steel, the LBT can produce bore accuracies of 0.000027″ (0.0006 mm) for diameter, roundness, and taper – from first part to last.

“We are currently honing about 80 percent of what we make and will do more as we acquire the tools in different calibers,” said Dichter. “Although there is a trade-off in cycle time and abrasive cost for additional honing, we are still able to run our reamers two to three times longer than when we lapped alone. With a hand lap, the time and effort increase when the reamer is getting dull.”

After honing, each barrel is inspected again before rifling with a pull-button. Pac-Nor makes its own Accu-Twist carbide rifling buttons and can provide different rifling styles, including polygonal, per the customer’s choice. A button is attached to a rod and the rod is pulled through the barrel. The company’s hydraulic rifling machine utilizes a CNC-machined twist bar with a helix angle that matches the twist rate requested by the customer. The final twist rate is confirmed afterward using a Barrel-Scan electro-optical twist measurement system.

The barrel is then stress-relieved in a tempering furnace, followed by contouring of the outer shape and final, finish lapping of the bore. “During the finish lap, you can really tell the difference between a bore that was honed before rifling and one that was lapped,” said Dichter. “You can easily sense any remaining tight or loose spots in the bore. The diameter uniformity and roundness of the honed bore are superb. The lap also feels different in a honed bore.”

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel

In competitive shooting where winning scores may be separated by thousandths of an inch, a few millionths of an inch improvement in the uniformity of a Pac-Nor barrel may make a big difference for a skilled shooter. For more information, visit www.sunnen.com or contact:

Sunnen Products Company
Mr. Bob Davis
Global Communications Mgr.
Sunnen Products Company
Tel: 314-781-2100
bdavis [at] sunnen.com

About Pac-Nor Barreling Inc.
Pac-Nor Barreling is a true custom manufacturer catering to bolt-action rifle shooters. The company’s principle markets are law enforcement, military, competitive shooters and hunters. Started in 1984 by avid shooter and company President Chris Dichter, Pac-Nor is now in its second generation under his son, Casey. In addition to barrel manufacturing, the shop will install the barrel on a customer’s action, or add features such as muzzle brakes or fluting on bolts and barrels etc.

The shop runs two shifts per day. A day shift of ten people produces 30-40 custom barrels of different calibers in 416R stainless or chrome-moly steel. A night shift of three people produces one type of barrel — about 50 AR-15 barrels per day for a rifle OEM.

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May 8th, 2016

A Mother’s Day Message…

Mothers' day mother's holiday grizzly video

“God could not be everywhere, and therefore he made mothers.” — Rudyard Kipling

Today is Mother’s Day. There are more than 85 million mothers in the United States, and today is the day we recognize all those ladies who brought life into the world.

This Editor lost his mother last July, so this Mother’s Day is particularly poignant — my first without her. Be good to your mother, cherish her, and love her without fail… always. In her latter years, attend to her needs, help her with her health, and take time to bring brightness (and laughter) into her life. Let her know that you appreciate all the sacrifices she made, and that you are grateful for all that she did for her children and family.

This Mother’s Day tribute was created by another man who recently lost his mother. It will help all of us appreciate all the things our mothers did for us…

Here are some quotes for Mother’s Day:

“Only mothers can think of the future — because they give birth to it in their children.” — Maxim Gorky

“Men are what their mothers made them.” — Ralph Waldo Emerson

“Such a mysterious business, motherhood. How brave a woman must be to embark on it.” ― M.L. Stedman

“All that I am or ever hope to be, I owe to my angel mother.” ― Abraham Lincoln

Photo credit to Grizzly Industrial.
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May 8th, 2016

Polly Tubb… Talented Shooter and Mother of a Champion

Pauline Polly Tubb David Tubb NRA High Power Championship Champion

Since this is Mother’s Day, here’s a story about one very special mother — a talented lady shooter who also reared one of the greatest marksmen in history, David Tubb.

Pauline Polly Tubb David Tubb NRA High Power Championship ChampionWe expect you’ve heard of David Tubb, 11-time NRA National High Power Champion. Without question, David is one of the greatest rifle shooters who ever lived. What you may not know is that David came from a family of shooters. David’s father, George Tubb, was a nationally-ranked High Power competitor. What’s more (now this may surprise you), David’s mother “Polly” was was a great shooter in her own right. When she wasn’t rearing a future Champion, Polly was hitting the X-Ring at rifle matches.

Pauline (“Polly”) S. Tubb of Canadian, Texas, earned several rifle championships during the course of her shooting career. In this photo, Polly took a moment to appear for a photo after winning the 1962 National Woman’s Bolt Rifle championship at Camp Perry. One shooter who competed against Polly observed: “I was there as a 1962 Pennsylvania State Team junior! I remember Polly. She beat some of the best Army and Marine shooters and always did it with style and good humor.”

Archive photo courtesy Civilian Marksmanship Program, TheCMP.org.
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