Case Cleaning & Consistent Capacity

[ThunderDownUnder]

A lot of shooters weigh and batch their cases to ensure consistent capacity. The necks of cases get brushed for consistent neck tension and the cases tumbled to keep them clean. Same process over and over thru the life of the case.

What about the build up of soot and crud inside the cases? Sometimes during the cleaning, reloading process, pieces of this crud drop away from the inside of the case and come out thru the neck for us to get a look at. While your looking at this piece of curved grey crud that resembles some sort of broken case liner, do you ever wonder what it does to the case's capacity?

I have and thats why I use an ultrasonic cleaner, to keep both the inside and outside of the cases clean. I could be wrong but if the capacity of the case decreases as the crud builds up. Then it effectively reduces the chamber size and would change the pressure produced from that of an equivalent clean case.

Its interesting that we recognize the need to brush out the necks because of crud build up but we ignore the diminishing case capacity. Can anyone offer any info on the effects this would have?

 

[Preacher]

Seems as someone has there head out of the sand on internal capacity being diminished with all that build up inside a case...
Thats why I use a Ultra Sonic to clean my cases.......
Kinda like using restrictor plates on NASCAR carbs I would think....

 

[dmickey]

Apparently, someone needs to measure case capacity after each firing to see if there even is a measurable change in case capacity. :idea: Any volunteers?

 

[ThunderDownUnder]

Apparently, someone needs to measure case capacity after each firing to see if there even is a measurable change in case capacity. :idea: Any volunteers?

Yeah, it seems ridiculous but we shooters got to the nth degree to get the most accurate round. I have a number of top shooter friends that are happy to just let the crud fallout. The worst part is that their accuracy doesnt seem to suffer.

I would like to know if anyone has measured velocity with a clean case and with a dirty,internal build up) case and just what the difference might be.

 

[Fred Bohl]

Back when beginning to use ultrasonic case cleaning, part of the motivation was to get the inside clean based on the assumption in this thread that it would affect capacity and ultimately performance to allow burnt residue to build up inside the case. An experiment was done to test this hypothesis.

The intent was to take 30 cases of identical initial capacity and track three lots of 10 each: lot 1 not cleaned; lot 2 tumbled media cleaned; and lot 3 ultrasonic cleaned.

Note that the load used 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.

The simplified results over 20 reloads of each were as follows:

Lot 1,not cleaned) - 0.3 to 0.4 gr. loss of capacity, 5 to 8 fps greater ES.
Lot 2,tumbled media cleaned) - 0.1 to 0.3 gr. loss of capacity, 4 to 6 fps greater ES.
Lot 3,ultrasonic cleaned) - no loss of capacity, no detectable change in ES.

NOTE 1: 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.

NOTE 2: 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.

 

[ThunderDownUnder]

Back when beginning to use ultrasonic case cleaning, part of the motivation was to get the inside clean based on the assumption in this thread that it would affect capacity and ultimately performance to allow burnt residue to build up inside the case. An experiment was done to test this hypothesis.

The intent was to take 30 cases of identical initial capacity and track three lots of 10 each: lot 1 not cleaned; lot 2 tumbled media cleaned; and lot 3 ultrasonic cleaned.

Note that the load used 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.

The simplified results over 20 reloads of each were as follows:

Lot 1,not cleaned) - 0.3 to 0.4 gr. loss of capacity, 5 to 8 fps greater ES.
Lot 2,tumbled media 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.

NOTE 1: 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.

NOTE 2: 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.

Wow, thanks Fred! I wonder how much more the build up and diminishing case volume would be over a long period of reloading?

 

[Fred Bohl]

ThunderDownUnder

I should have noted in my post that I used 6mmBR for those tests and 30.5 gr. of Reloader 15 behind 107 gr. SMKS. I would suspect that different powders, load weight and total case capacity might produce very different results.

A local shooter reported doing the 20 reload no clean test on a 308 that gave a loss of capacity of 2 gr., doubled ES and 90 fps. velocity loss. However, I don't have any details on his load,% capacity, compressed or not, load weight or powder type).

 

[ThunderDownUnder]

ThunderDownUnder
A local shooter reported doing the 20 reload no clean test on a 308 that gave a loss of capacity of 2 gr., doubled ES and 90 fps. velocity loss. However, I don't have any details on his load,% capacity, compressed or not, load weight or powder type).

Thankyou Fred, that seems to indicate to me that my investment in a ultrasonic cleaner, based on an assumption is now proved to be fact. A 2gr capacity loss in a 308W is going to seriously affect accuracy as the velocity loss of 90fps is very significant.

 

[Fred Bohl]

ThunderDownUnder

I use ultrasonic cleaning for case cleaning because I get completely clean case,inside, outside, flash holes and primer pockets) quickly and easily.

You may have read the bulletin comments about the inside of the neck being so clean after the ultrasonic cleaning that there is a significant increase in the force required to seat bullets as compared to cases with residual carbon deposits. I find that the amount of increase in seating force is very dependent on how rigorous the reloader was in brushing out case necks before switching to ultrasonic cleaning.

I've experimented with lubricating the inside of the case neck using both the Neco Dry Neck Lube Kit and the similar Redding Imperial Application Media with Imperial Dry Neck Lube. So far I have found the following:

More consistent seating force is attained by dipping the bullet base in the media/lube mix than by dipping the case neck.*

I can detect no difference in results between the two products.

The Redding product is less messy to use and clean up.

* For those that lube the exterior of the case neck before neck sizing, it would not be necessary also dip the bullet base in the media/lube as sufficient lube will remain on the inside of the neck to ease bullet seating.