May 9th, 2017

High-Tech Honing — Major Advance in Barrel Making

Sunnen honing barrel hone CNC computer honer machine Pac-nor

Some custom barrel makers are now honing barrels (after drilling) to improve bore diameter uniformity, smooth the interior finish, and reduce barrel lapping times. For years, large-scale manufacturers of hammer-forged barrels have employed honing. Now the process is being used by smaller, “boutique” barrel-makers. This article explains how and why barrel honing is done. Take the time to watch the video. For anyone with an interest in barrel-making, this video is an eye-opener…

Barrel Honing Process Demonstrated (Worth Watching!):

Barrel Bore honing cut-rifled rifling hammer forging accurateshooter.com

For custom barrel makers, honing is a time-saver and cost cutter. A few minutes on a honing machine can cut lapping times in half, leaving a cross-hatched surface finish in single or low double-digit Ra. Honing is the same process used to make diesel fuel injectors with bore roundness and straightness controlled to fractions of a micron (<0.000040″), with surface finish Ra ≤0.15 µm (6 µin).

A key manufacturing process used for hammer-forged barrels is now getting attention from the makers of custom button-rifled barrels. This process is precision bore-honing. Honing produces a high-quality bore surface fast, which is critical to hammer forging. (Why is honing so important with hammer forging? Surface finish is the one feature of the barrel that cannot be controlled in hammer forging. Surface imperfections in a barrel blank tend to be amplified as the blank is formed on the rifling mandrel. And if the bore is chromed afterwards, imperfections in the surface finish become even more obvious.)

Honing dramatically improves bore diameter size uniformity and accuracy, surface finish and roundness throughout the length of the barrel. It can certainly be used in place of a pre-rifling lap. The chief difference between a lapped and honed bore is the direction of the finish lines in the bore. Honing leaves fine spiraling crosshatch lines, while a lap leaves lines going longitudinally in the bore. After rifling the manufacturer can remove the crosshatch finish with a quick lap if desired. Honing is fast, accurate, and can be automated. Its surface quality and geometry can duplicate lapping, except for the longitudinal lines of the lapped finish.

Frank Green of Bartlein Barrels told us: “We worked with Sunnen and we did all the initial testing on the prototype machine for them. The machine works great! We ordered and received last year a new manufactured machine with the changes we wanted on it and we just ordered a second one a month or so ago. Should be here next month.”

(more…)

Permalink - Videos, Gunsmithing, Tech Tip 8 Comments »
May 9th, 2017

Watch Out for Bullet Nose Contact in Short Seating Stems

Seating Stem Glen Zediker

Clearance Check — Remove the seating stem and drop a bullet into it. The farther down the ogive or nose-cone the step recess grips the bullet, the better. If it’s only pressing down against the bullet tip, a crooked seat is assured, along with inconsistent seating depth. — Glen Zediker

Some folks acquire a new seating die and then are surprised to find their hand-loads show crooked bullets and/or inconsistent seating depth. The problem could be a mis-match between the bullet and the die’s seating stem. In some case, particularly with long, streamlined bullets, the bullet tip can actually touch the bottom inside of the stem. This can cause a variety of problems, as Glen Zediker explains…

Invest in a Good Seating Die
Reloading Tip by Glen Zediker
The bullet seating operation is the “last thing” that happens and it’s also the one thing that can corrupt the care and treatment given to the quality of the loaded round prior. A sleeve-style seater, well-machined, goes a whopping long ways toward preserving alignment, and, therefore, concentricity. Also make sure that the stem in yours comes to rest well down onto the bullet ogive, and, above all else, is not contacting the bullet tip! That will wreck a round.

If you have this problem, you should contact the die maker — some will offer a different seating stem expressly designed for longer, pointier bullets. This “long bullet stem” will normally drop right into your existing die. If you plan to run long, VLD-style bullets you should request the special seating stem right from the get-go.

This tip comes from Glen’s newest book, Top-Grade Ammo, available at Midsouth Shooters Supply.

Permalink Bullets, Brass, Ammo, Reloading No Comments »
May 9th, 2017

How Bullets Are Made — Videos Reveal Process at Barnes Bullets

Barnes Bullets FactoryMany of our readers have been interested in learning how modern bullets are made. While a “boutique” bullet-maker, supplied with appropriate cores and jackets, can craft bullets using relatively simple hand dies and manual presses, factory production is different. The major bullet-makers, such as Barnes, employ huge, complex machines to craft their projectiles on an assembly line.

Modern hunting bullets are made with a variety of sophisticated (and expensive) machines, such as Computer Numerical Control (CNC) lathes, giant multi-stage presses, and hydraulic extruding machines that draw lead ingots into lead wire. Barnes offers an “inside look” at the bullet production process in a series of videos filmed at its Mona, UT factory. We’ve embedded four videos from the series here. These videos can also be viewed on the Barnes Bullets YouTube Channel.

Milling Slots in TSX All-Copper Bullet
This video shows how the slots (between the drive bands) in the TSX all-copper bullet are cut. The slots reduce the bearing surface that contacts the rifling. This helps reduce friction and heat, extending the life of barrels used with all-metal, drive-band bullets:

Varminator Bullets Produced in Jumbo Transfer Press
Here is the transfer press used in the production of Varminator and MPG Bullets. The process begins with a giant spool of flat copper material. The copper is stamped into jackets and eventually the formed Varminator bullets are ejected one by one into a bucket.

CNC Lathe Turns Bullets Automatically
In the video below, a Bar-Feed CNC crafts mono-bloc bullets from metal bar stock. Barnes uses a small CNC lathe to turn .50-caliber bullets from brass bar stock. We’re not sure which bullet is being made in this video. The material looks to be sintered metal. In the close-ups you can gold-colored shavings from when the machine was previously used for CNC-turned brass bullets.

Accuracy Testing in 100-yard Tunnel
Barnes regularly tests bullet samples for accuracy. In the video below, a Barnes technician loads sample rounds and tests them for accuracy in a 100-yard tunnel. The rounds are shot through a special fixture — basically a barreled action connected to parallel rods on either side. This allows the testing fixture to slide straight back on recoil (see it move back at 1:07-08 minute mark). Note how the tester actuates the trigger, which is oriented upwards, just the opposite of a normal rifle. The technician taps the upward-pointing trigger shoe lightly with a metal rod. Could this upside-down trigger orientation be useful in benchrest shooting — perhaps with railguns? It could make for an interesting experiment.

Story suggestion by EdLongrange. We welcome reader submissions.
Permalink - Videos, Bullets, Brass, Ammo 3 Comments »