Doppe skoonskuur / cases and abrasives?

What type of scouring pad?

Sounds a bit aggressive for my tastes.

A super clean case will not grip the chamber walls as effectively as a slightly tarnished one. This means that bolt thrust is heightened and the lugs or similar retaining metal takes a beating and can shear off due to fatigue. Combined with heavy charges this can cause serious damage to the action or the shooter.

I stick to dry tumbling and ensure a good grip. The loaded round may not look bright and shiny, but functions perfectly.

An old and worn regular sponge scourer (yellow-and-green) seems to work well. The cases are noticeably coarser.

I am not sure whether they remove too much material from the case. My reloads still work fine, but I shoot too little to make a comprehensive deduction.

If it is the plastic/nylon type green scourer, then go ahead and scout away. You'll probably replace the drill motor brushes before any material change in thickness happens with the case.

A bright, shiny case should be gripped better in a clean chamber than a tarnished case. The caveat being that all lube have been removed from the case and chamber before firing.

How does one remove all the lube?

I wash them again after resizing, but when tumbling a few of the cases always ends up dirty and clogged due to oil.

The green part of the scouring sponge thingy is basically Scotch Brite. This is a pretty agressive abrasive.

Wikipedia:
"The structure of Scotch-Brite pads is created by a sparse unwoven polymer such as cellulose, nylon or spun polypropylene fiber. Products use several variations of hardening and abrasive materials, such as aluminum oxide (alumina), titanium dioxide and resins.[1] Although the base polymers may be considered benignly soft, the composition with other materials greatly enhances their abrasive powers; to the extent that a heavy-duty Scotch-Brite pad (which contains both aluminum oxide and titanium dioxide) will scratch glass."

In my experience it is a more aggressive abrasive than steel wool. As with steel wool, make sure you do not get little bits left behind that find their way into the gun.

I doubt that the little bit of brass removed will measurably thin your brass, if you only polish it until it is shiny. I have often wiped my cases clean with a scouring pad after washing in my Citric Acid and Sunlight mix. This is done wet, so any residues are hopefully washed off, and the water seems to soften the pads a bit. I did not notice any scratch marks afterwards. Cases were turned by hand only. This was done in stead of dry tumbling, when I was in a hurry to get the cases loadable.

I do think that a moderate tarnish (oxidation) on the cases acts as a lube. On handgun cartridge with Tungsten Carbide sizer die, the un-lubed tarnished cases generally have less resistance than shiny clean ones. I guess the same applies in a chamber, but that's just my guess.

Lube in a chamber at normal to max working pressure is definitely not recommended. Locking lug set-back or shear may be problem on AR's, but I have also seen it happen on a Brno ZKK602 that was converted to 460 Weatherby. This is an extreme example. Normal medium caliber rifles will likely not suffer from this condition, even with some abuse.

Interestingly, under certain conditions lubed cases can actually extend case life. If you full length resize every time, the case will stretch quite a bit until it cracks or separates. If it is lubed, it will move back against the breech face without stretching. I would not recommend this, but it may serve the purpose of case forming with a mild load.

Anything can be over-done to the point where it can cause damage. Do it within reason, and it will be beneficial.

Quote 223 ******************* Interestingly, under certain conditions lubed cases can actually extend case life. If you full length resize every time, the case will stretch quite a bit until it cracks or separates. If it is lubed, it will move back against the breech face without stretching. I would not recommend this, but it may serve the purpose of case forming with a mild load.

Anything can be over-done to the point where it can cause damage. Do it within reason, and it will be beneficial.
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been some time since I read as "new" a piece of "I did not know" - Coming from 223 I guess its fact.
This opens a whole new book for .303 case life, first shot from lubed case ?
This is VERY interesting indeed.

Quote 223 ******************* Interestingly, under certain conditions lubed cases can actually extend case life. If you full length resize every time, the case will stretch quite a bit until it cracks or separates. If it is lubed, it will move back against the breech face without stretching. I would not recommend this, but it may serve the purpose of case forming with a mild load.

Anything can be over-done to the point where it can cause damage. Do it within reason, and it will be beneficial.
************************************************
been some time since I read as "new" a piece of "I did not know" - Coming from 223 I guess its fact.
This opens a whole new book for .303 case life, first shot from lubed case ?
This is VERY interesting indeed.

On a "Smelly" with it's relatively flexible action (due to the rear locking lug setup), this might be a poor choice, since we already have the better rubber band or O-ring trick to keep the case head firmly back against the breech face.

Lubing a cartridge is a very bad idea. It increases bolt thrust by at least the tensile strength of brass. Not something you want to do with a World War era rifle built to save steel.

An oiled cartridge is called the "poor man's proof load".

Lubing a cartridge is a very bad idea. It increases bolt thrust by at least the tensile strength of brass. Not something you want to do with a World War era rifle built to save steel.

An oiled cartridge is called the "poor man's proof load".

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Use a fireforming load, not a hunting charge

I'm trying hard to get my head around this discussion. Its all theory and here say, but there is no data and no measurable units.

Has anybody done a study: lets take two identical rifles, and feed 1000 rounds of brass (factory finished with some rough tarnishing) as a control, and then feed the other gun 1000 rounds of the same brass that has been polished to a gleaming shine, then examine the two rifles for bolt thrust damage. Perhaps add a third group, where the chamber/brass is lubed with something heat proof like molly or HBN. I'm sure in the past, when militaries where doing the early development work, there must be some data on this. Otherwise, this discussion is going nowhere.

The MOD published guidelines on what a lubricated round would do in a smelly and why it was was to be avoided when proofing. The increase in bolt thrust was statistically significant to say the least.

The MOD published guidelines on what a lubricated round would do in a smelly and why it was was to be avoided when proofing. The increase in bolt thrust was statistically significant to say the least.

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Use a fireforming load, not a hunting charge

The MOD published guidelines on what a lubricated round would do in a smelly and why it was was to be avoided when proofing. The increase in bolt thrust was statistically significant to say the least.

Thanks, I would be surprised, if such an experiment was not done. I wonder of the taper on a case wall would exacerbate the situation, and a modern straight walled case would negate the problem?

Thanks, I would be surprised, if such an experiment was not done. I wonder of the taper on a case wall would exacerbate the situation, and a modern straight walled case would negate the problem?

I'll try and dig the document out. It dealt with the procedures for poofing SLMLEs and was really interesting in a number of ways. One was that the Enfield action was up to a fair bit more pressure than legend would suggest. Another was the very strict instructions around chamber and cartridges being completely free of grease or oil due to the enormous increase in bolt thrust invalidating the results if they weren't.

The MOD published guidelines on what a lubricated round would do in a smelly and why it was was to be avoided when proofing. The increase in bolt thrust was statistically significant to say the least.

Thanks, I would be surprised, if such an experiment was not done. I wonder of the taper on a case wall would exacerbate the situation, and a modern straight walled case would negate the problem?

Yes, the taper does make the problem worse.

Case taper and pressure are some of the factors that govern ease of extracting a fired case. If there is no taper, cases from mid to high pressure cartridges are difficult to extract. For that reason there are very few straight (parallel) wall cartridges. Those that exist are low pressure with a few exceptions. Most notable is the 5.7 which has a dry lubricant on the case to aid extraction. Cleaning those cases in a tumbler removes the coating and makes them unusable.

Excessive taper causes high bolt thrust and a loss of useable case volume. Also makes it difficult to design high capacity magazines.

Most historical designs have a pronouced taper. That is why PO Ackley could improve cartridges; "Ackley Improved" or AI. He found that reducing the taper and changing shoulder angles not only gave increased powder space, but also allowed a slightly higher chamber pressure.

https://gundigest.com/gear-ammo/ammunition/experimenting-with-bolt-thrust

I found this quite interesting in the subject of bolt thrust and case taper.

I think bolt thrust is a massive demon in the dark for most people, never seen, never exposed, just there waiting. It is such a huge, massive, catastrophic potentiality, sitting there - right nexter your management center.
Every shot.