September 1st, 2008

Ultrasonic Case Cleaning — Does It Really Help Maintain Load Consistency?

As a cartridge case is reloaded multiple times, burnt powder residue and carbon builds up on the inside of the case. Unless the case interior is cleaned in some fashion, eventually you’ll see a reduction in case capacity. One of our Forum members from Australia wonders about the effects of reduced case capacity: “If the capacity of the case decreases as the crud builds up, then it effectively reduces the chamber size. Wouldn’t that change the pressure produced from that of an equivalent clean case?”

Ultrasonic Cleaning Example:

Interesting Test of Case Capacity Changes
Forum member Fred Bohl has actual test results that can help answer the above question. Fred proved that, over a 20-reload cycle, the case capacity of uncleaned cases did, indeed, decline a small amount. However, surprisingly, this did not seem to affect the actual chronographed velocity of the load. ES did increase, but Fred believes the higher ES was due to changes in case-neck tension, rather than due to the slight reduction in case capacity.

Fred reports: “Back when beginning to use ultrasonic case cleaning, part of the motivation was to get the inside clean based on the assumption that allowing burnt residue to build up inside cases would affect capacity, and, ultimately, performance. An experiment was done to test this hypothesis. The load used, 30.5 grains of RL15 behind 107gr SMKs in a 6mmBR, was selected for best group and lowest ES in prior load development. It turned out to be 92% of initial case capacity and neither “full” or compressed. (I would suspect that different powders, load weight, and total case capacity might produce very different results.)

We took 30 cases of identical initial capacity and tracked three lots of 10 each:

LOT 1: No Internal cleaning
LOT 2: Cleaned with media in tumbler
LOT 3: Cleaned with Ultrasound machine

Each case (in each lot) was shot and reloaded 20 times. The simplified results after 20 reloads of each lot were as follows:

Lot 1 (not cleaned) – 0.3 to 0.4 gr. loss of capacity, 5 to 8 fps greater ES.
Lot 2 (tumble cleaned) – 0.1 to 0.3 gr. loss of capacity, 4 to 6 fps greater ES.
Lot 1 (ultrasonic cleaned) – no loss of capacity, no detectable change in ES.

FINDINGS
There was no detectable correlation of velocity change to the lots. An oddity was that on very hot days Lot 1 velocities were, occasionally, slightly higher. [Editor’s note: That does suggest that the carbon build-up inside the uncleaned cases might cause a slight increase in pressure that shows up on hot days. Fred has posted that “A local shooter reported doing the 20 reload, no clean test on a .308 that gave a loss of capacity of 2.0 grains, doubled ES and signficant velocity changes. However, I don’t have any details on his load weight or powder.”]

NOTE: From results of another ongoing test, I believe the above differences in ES are probably due more to variance in bullet grip tension than case capacity. The ultrasound cleaned cases (LOT 3) did maintain the lowest ES, but we are not 100% sure of the reasons why. More consistent bullet seating might be the reason.

[Editor’s comment: Jason found that with his ultrasonically-cleaned cases, the inside of the necks got so “squeaky clean” that he needed to use dry lube in the necks. Jason uses the $10.95 dry lube kit from Neconos.com. This applies ultra-fine Moly powder to the neck using small carbon steel balls]

Neconos.com moly neck lube

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September 1st, 2008

Bore-Stores and GoldenRods on Sale at MidwayUSA

For storing fine firearms in a gunsafe or storage locker, we recommend Bore-Stores. These thick, synthetic fleece bags are treated with silicone and a special rust inhibitor to safeguard against rust and corrosion. Bore-Stores also cushion your rifles, protecting against nicks and dings while you’re moving your guns in and out of the safe.

Bore-Store Gun Case

Right now, through the end of September, MidwayUSA has most popular sizes of Bore-Store bags on sale. Bags for 4″ and 6″-barreled pistols are marked down from $5.89 to $4.99, and the 46″ Scoped rifle Bore-Store bag (item 570349) is just $9.99, reduced from $11.49. NOTE: Even if your rifle measures a bit longer, we have found this bag is large enough to fit a Benchrest-style rifle with up to 28″ barrel. For shorter guns with big scopes, we recommend the 42″ AR15 case (item 360601).

Bore-Stores are outstanding products, much better than the thin “gun socks” made by other companies. The fleece material is breathable, so it wicks away moisture from the firearm. By contrast, typical hard cases with “eggcrate” foam interiors attract and retain moisture — they can actually breed rust on your guns. Likewise, most zippered soft cases retain moisture.

GoldenRods on Sale Too
GoldenRods are electric heating elements that help prevent corrosion in your gunsafe by maintaining a constant temperature that is above the dewpoint. This prevents rust-breeding moisture from condensing on your guns. Both large and small GoldenRods are on sale this month at MidwayUSA, starting at $15.99 marked down from $19.99. The largest “gold” model (item 621013), which protects up to 300 cubic feet, is now $10.00 off, marked down to $29.99 from $39.99.

goldenrod dehumidifier

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