May 21st, 2013

Ultrasonic Cleaning, Case-Neck Friction and Bullet Seating

ultrasonic cleaningOur IT guy, Jay (aka JayChris in the Forum), was having some issues with his .260 AI. A load with known accuracy had suddenly and mysteriously stopped shooting well. Jay couldn’t figure out what was going wrong. Then he remembered he had cleaned his brass using a powerful ultrasonic machine.

He inspected his brass carefully and saw that the ultrasonically-cleaned necks were so “squeaky clean” that he was actually scratching the jackets on his bullets when seating them. As well, Jay noticed that it took more force to seat the bullets and the seating force became less uniform case to case. Jay solved the problem by applying NECO Moly dry-lube inside the necks of his brass before seating the bullets.

The Perils of Ultrasonic Brass Cleaning by JayChris
I rotate my brass so that I can keep track of each firing, so I keep a “clean/ready to load” bin and a “fired” bin. I have 400 pieces of .260 AI brass. So, all of it was on its first firing (after doing a Cream of Wheat fire-forming) until I hit the 400-round mark. To my surprise, things went south at the 500-round mark. The first time I noticed it (according to my range log) was at a match last year, when I dropped several points and had some vertical stringing issues. After that match, I had 400 rounds through the barrel and all of my brass had a single firing on it. So, it was time to clean.

ultrasonic cleaningI have used an ultrasonic cleaner for a while now. I recently got a more powerful Ultrasonic cleaner, although I don’t know if that makes a difference. My brass comes out dry and squeaky. Emphasis on the “squeaky”.

I found that my new US machine may have been getting the necks TOO clean. After ultrasonically cleaning my brass, I had noticed that it required a little more force to seat the bullets, but I didn’t really think too much about it. But then, after going over my ordeal with a shooting buddy and going over my process in minutiae, we had an “AH HA” moment when it came to cleaning (he uses good ol’ vibratory cleaning).

So, I used some moly dry-lube to pre-lube the case necks and took some rounds out to test at 200 yards. I used my last known good load and sure enough, the vertical flyers disappeared! I shot two, 10-rounds groups with .335 and .353 MOA vertical dispersion, which is consistent with the results I was originally getting.

Other folks have suggested necks may get “too clean” after ultrasonic cleaning. It was pretty sobering to actually witness, first hand, what can happen when brass is “too clean”. I had read some discussions of issues with neck friction/bullet seating after ultrasonic cleaning, but, frankly, I dismissed the idea. Now I understand. The “too clean” effect doesn’t seem to affect my Dasher at all (perhaps because Dasher necks are very short), but on the bigger .260 AI, it definitely does.

Close-Up Photos of Case-Necks

Here are photos Jay took with a microscope. You can see the difference between tumbled brass and ultrasonically-cleaned brass. Jay says: “Here, in sequence, are the Ultrasound-squeaky-clean case neck, a case neck after treatment with NECO moly dry-lube (you can see the particles that will help coat the neck during seating), and, finally, the neck from a case cleaned with corncob media in a vibratory tumbler. You can clearly see how much smoother the inside of the tumbled neck is. Yes, it’s dirty, but it’s also very, very smooth.

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ultrasonic cleaning

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Close-Up of Scratched Bullet

Here is a close-up of a bullet that was seated in an ultrasonically-cleaned (“squeaky clean”) neck, with no lubrication. You can clearly see the damage done to the jacket — in fact, in a couple spots you can see the lead core through the scratches! Jay also observed that quite a bit more seating force was required to seat the bullet in a “squeaky clean” neck.

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NOTE: The bullet jacket is naked — NOT coated in any way. It looks a little dark because of the shadow from the microscope lens, and the high contrast.
Permalink Bullets, Brass, Ammo, Reloading, Tech Tip 5 Comments »
May 21st, 2013

6.5 Creedmoor Featured in Shooting Sports USA Archive

We often get questions about the 6.5 Creedmoor Cartridge — folks ask where they can find good resources for this cartridge, which is popular with Across-The-Course, High Power, and tactical shooters. We did some searching and found that the August 2011 digital edition of Shooting Sports USA has a good article for all fans of the 6.5 Creemoor.

6.5 Creedmoor Development of the 6.5 Creedmoor Cartridge
In the August 2011 Edition of Shooting Sports USA you’ll find a lengthy feature on the 6.5 Creedmoor cartridge. This story covers the origin of the cartridge and its performance both as a match cartridge and as a hunting round. Hornady Chief Ballistician Dave Emary explained: “the original intent of the cartridge was as an across-the-course match cartridge. We envisioned it as an off-the-shelf round that would produced the accuracy and ballistics to compete in all match disciplines right out of the box. At the same time we realized that the same characteristics would make an exceptional hunting cartridge with the right bullets.”

6.5 Creedmoor

6.5 Creedmoor Annealing6.5 Creedmoor Brass No Longer Washed After Annealing
Here’s an interesting update on Hornady 6.5 Creedmoor brass and loaded ammo. In a move to improve case quality and neck uniformity, Hornady recently changed the 6.5 Creedmoor production process, eliminating the case-washing step after annealing. So now you will see annealing coloration on 6.5 Creedmoor brass, just like on Lapua brass. Dennis DeMille of Creedmoor Sports wanted to improve the consistency/uniformity of 6.5 Creedmoor case-necks. At Dennis’ suggestion, Hornady conducted tests which showed that the “standard industry practice” of washing brass could potentially alter the necks in undesirable ways. Bottom line, unwashed annealed brass was determined to have an accuracy edge over washed brass. Looking at these results, Hornady decided to forgo the post-anneal washing process. As a result, the latest 6.5 Creedmoor brass now displays the distinctive coloration left by neck/shoulder annealing. Learn something new every day, eh?

Permalink Bullets, Brass, Ammo, Reloading 2 Comments »