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Polished cases and bolt thrust?

This topic can be found at:
https://forums.accuratereloading.com/eve/forums/a/tpc/f/2511043/m/8941032321

28 December 2009, 16:53
greenjoy
Polished cases and bolt thrust?
I didn't want to hijack poster Naphtali discussion on "Paste waX and chamber pressure" so I started this new discussion for my question.

Am I screwing up when I add a teaspoon of Dillon liquid case polish to my tumbler media prior to cleaning my very tapered 375H&H cases?

I do wash the cases after, but I doubt I'm removing the thin layer of dried polish.

Lately I've been using a zip trim and an Krazy Kloth to polish these case till there almost white in colour. I'm sure this process leaves a thin layer of polish on the case.

375H&H case are known to stretch on firing and mine do just that.

Will the polished cases have a reduce life due to increase stretch or will it increase their life a little by allowing the whole case to move back to the bolt face and just the case shoulder being fire formed to fill the shoulder space?

I hope I get at least one extra reload but I suspect a micron thick layer of polish barely qualifies as chamber lube.
28 December 2009, 17:22
Jim C. <><
Case stretch is a result of excessive resizing and/or a springy action. It's unlikely your action has much spring.

Polished cases will have little effect on bolt thrust, you would need to grease the cartridges for enough of that to matter. But what's the point of such a high polish?
28 December 2009, 17:24
Bob from down under
I think this die will help with the stretching.
Belted Magnum Collet Resizing Die
http://www.larrywillis.com/

I do not clean brass the way you are describing.
Why do you clean your brass like that?


Regards,
Bob.
28 December 2009, 17:53
woods
Hey greenjoy

There is a lot of pros and cons on this thread and some reading on Varmint Al's site.

Let us know what conclusions you have after reading those please.


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
29 December 2009, 06:27
greenjoy
I couldn't understand varmint al's site discussion too technical, although I did enjoy the graphs and pictures the amount of work he did....wow, my hat off to him.

As for the "this thread" link well it degenerated into the usual mess that is all to common on this forum, no facts backed by technology and numbers just the usual emotional feelings.

I like my brass shinny.
I only reload 30 to 40 rifle cartridges at a time and tumbling over night is no effort on my part.
Although rinsing them out and brushing the inside of the neck is tedious.
I do enjoy using the zip trim and Krazy Kloth polishing cloth step that I do, so I think I will continue doing.
To hell with worrying about bolt thrust.
29 December 2009, 09:07
woods
I ordered some of that Krazy Kloth cause I don't enjoy the mess of the Flitz.

What I gathered from all that was that it would be hard to get a slick enough finish with either the Flitz or your tumbler polish to have a coefficient of friction low enough to have a deleterious effect.

IMO the only time you have to worry about it with new cases. The forward movement of the case is stopped by the belt and the brass expands forward to the shoulder. The bolt thrust should not be significantly or even measureably increased because the case is polished. Whether it increases or decreases thinning at the web is up for grabs, probably no significant difference there either.


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
29 December 2009, 18:51
wasbeeman
In order to cling to the walls of the chamber, the brass would need to be clean and dry. Any substance that would impede that would cause bolt thrust, ie, a film left from a polishing agent.


Aim for the exit hole