How Ofteen do you trim Brass?

[Tozguy]

Must say thanks for your help in clearing up a personal (and perhaps popular) misconception that the .010'' below max trim rule applies to case length specs as published in reloading manuals. It makes more sense to base it on chamber length, because the case need only be .010'' shorter (and sometimes less) than the chamber. Measuring the chamber is much easier than it might seem at first glance.

 

[necchi]

A chamber cast won't do it.......

OK I get all the stuff about chamber necks being way long,, my 7-08 is .045 over sammi trim too recomendations!,,but whats wrong with a cerrosafe chamber cast??

I could see the difficulties trying to get a cast from a auto or pump,,but used in a break action single,,how can ya miss?

 

[Steve Blair]

A chamber cast cannot give you the dimension, referenced from the bolt face in battery to the chamber end, that you need.

 

[fdshuster]

The Sinclair gauge(s) are really very simple and easy to use, cost is minimal at approx. $7.00 for each caliber, re-usable, can be used for any cartridge of a dedicated caliber, (ex: 223 + 22-250 + 220 Swift, etc), and will give you the exact chamber length to three decimal places. I record that dimension and it is kept in each rifles log book for ready reference, same place where I keep headspace dimension, throat depth/bullet seating lengths, etc. I am running some of my closely fitted cases (Lapua 6BR & 6ppc) to within .005" of case length to chamber length, ex: 6BR case at 1.565" in a chamber length of 1.570". There is not even a trace of carbon in that area. The important thing to know is the actual length of your chamber, decide on how much clearence you are comfortable with, and trim (or not) accordingly. This is just another part of "precision reloading", no different than knowing what your headspace and throat dimensions are.

 

[necchi]

Thanks sleepygator, I just looked at my break action single shot again,,

I'm gonna have to send this gun in,,I can't find the bolt!

 

[Steve Blair]

The term "bolt" is a generic firearms term meaning the mechanism that blocks and holds the cartridge in the chamber. A synonym is the older term "breechblock." A bolt is currently accepted to mean a rotating breechblock. If you wish, I will revise my statement to:

"A chamber cast cannot give you the dimension, referenced from the breech face in battery to the chamber end, that you need."

 

[cliffy]

(sic) means error found in quote, but word left in error while repeating a quote. Sleepy, you used this term correctly: i.e. using too instead of to or two equals average grammar, such as I otherwise detect throughout this forum. We discuss firearm performance and not correcting grammar here, or we'd opt for a forum designated 'English 101 Firearms Colloquy.' Just a plea for amnesty regarding forgiveness to those who aren't English Instructors or Buffs. Respectfully, cliffy

 

[Steve Blair]

Cliffy,

I have never corrected your grammar or that of anyone posting to this forum. It is not for lack of opportunity. I do have an English degree. I have also designed and built firearms, served as VP, Marketing at a well known firearms company and demonstrated firearms in 17 countries. On this forum, I generally confine myself to matters regarding firearms, reloading, shooting and hunting.

But, any error should be identified when quoting. This is what I was taught and still believe is the correct approach. It was not intended as a slight or admonishment of the poster but merely good writing form. Anyone can succumb to inattention, type too quickly and enter two vowels.

Respectfully,

 

[Joe O]

this might be a stupid question but could you put a flat base bullet in a case and chamber it ? would you get a good measurement.
sport
[/
Never a stupid question.A flat based bullet inverted can't work because it would stop where the bullet diameter meats the lands,and you want to measure where the case neck would stop if it were too long.The Sinclair gage has a collar the same diameter as the outside neck.Tis way you can just trim .024 OAL back from the measurement of that chamber,rather than the Manual recomendations.I never trim untill after the first fireing,unless the case oths are obviously uneven.Once trimed,it will probably take quite a few firings ,depending on the case/caliber,before the neck will close under the .024 dimention

















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