Trimming brass to same length?

[PatMiles]

What is the purpose of trimming brass to the same length if the brass is not at the chamber length?
Advantages?

 

[Bc'z]

Consistency
In a word

 

[dgeesaman]

I just neck skimmed some of my brass. I turned to length first so that my neck turning would consistently kiss the shoulder.

 

[Big Mc]

What is the purpose of trimming brass to the same length if the brass is not at the chamber length?
Advantages?

As stated above Consistency Consistency !!!!!!

 

[Bart B.]

Most folks trim cases to a given length for convenience, squaring up case mouths and preventing case mouths being crimped into bullets if the firing pin drives them into chamber mouth shoulders. A few thousandths clearance is required

Case trimmers, remember that case's headspacing on their shoulder position their mouth in the chamber neck relative to their shoulder that's against the chamber shoulder when fired.

A batch of cases trimmed to 2.500" having a .004" spread in head to shoulder will have, when fired, a .004" spread in head clearance to the bolt face and where their mouth is relative to any place on the chamber axis. Such cases fire when their shoulder is against the chamber shoulder. Case heads are normally not held against bolt faces when fired.

 

[BenPerfected]

What is the purpose of trimming brass to the same length if the brass is not at the chamber length?
Advantages?

Most of the advantage leans toward Midway & Brownells. Sold my trimmer a few years ago.

 

[muleman69]

My Lapua and Nosler brass is so short that I may never have to trim except to square up the mouth and keep them all the same length. If I have to trim I will take just enough of for chamber clearance, Normally that is several thousandths over max book. I feel there is no need to over work the brass . Just my $.02

 

[mikecr]

Making them 'consistently' wrong, by over trimming, is the opposite of good reloading.
And there is no advantage in it (only detriment).

Better reloading is producing and managing best fit.

 

[PatMiles]

Gentlemen,
Thanks for the replies.
All the brass for my rifles is far short of the chamber length as measured so at this point I have no worries of the case mouth being driven into the forward end of the neck portion of the chamber. Squareness I get but at what point does the lack of squareness cause an issue in bullet release which would have to be the overriding issue as my brass is way short of max length, .016"-.020". I'll keep an eye on it though.
Thanks again,
Pat

 

[Bart B.]

Squareness I get but at what point does the lack of squareness cause an issue in bullet release which would have to be the overriding issue as my brass is way short of max length, .016"-.020".

I don't know of any test results proving tiny dimensional variables in case mouth squaring changing how far bullet trajectories vary from their norm. All other cartridge, rifle, shooter and environmental variables need be about zero to reveal case mouth out of square issues.

 

[hikfromstik]

I always trim every case to the same length . Consistentsy is the name of the accuracy game . If one piece is trimmed a different length to the rest then that bullet will have different neck friction on it . The exploding powder expands the neck , so if one neck is longer/shorter it will affect the pressure . My most accurate loads have always been with properly trimmed brass .

 

[Bart B.]

If one piece is trimmed a different length to the rest then that bullet will have different neck friction on it.

Yes. Consider this.....

A bullet gripped by .250" of neck length needs 10 pounds of force to start pushing it out. How much force is needed if it's gripped with .255" of the neck?

If a 30 caliber bullet is used, what's the psi level needed to start pushing it out for each grip length?

 

[Dusty Stevens]

if you have space in front of your case mouth, lets say .030 so you say youll never have to trim right?, then you get a piece thats longer. you have carbon in that recess and you have .002 shoulder clearance (lets call it headspace to simplify) then as the firing pin drives the case forward the longer ones slam into that carbon ring where the shorter ones do not. we got people weighing primers and bullets to the .0001gn why would you possibly not trim your brass to all the same length? its mind boggling.

 

[Mulligan]

OK, I understand most reply’s here support the notion that is matters not if cases vary in length several thousandths of an inch.

I personally have always watched closely the case length as a reloading mentor of mine (Irishman named Carson Teany) drove home the point about factoring in the narrowing of the chamber neck diameter due to carbon forward of the case mouth. The Ol’Boy made it clear that if you shot shorter brass and then longer, the longer may have a bit more pressure due to clearance or “carbon crimp” as he said. Now Carson was a SR Benchrest shooter and maybe little things mattered more to him?????

I’ve never set a record, nor am I on the cutting edge of this stuff.
Interested is all.
CW

 

[Steve Ladino]

What is the purpose of trimming brass to the same length if the brass is not at the chamber length?
Advantages?

The reason is it's part of the accuracy equation. Those of us after the most accuracy we can find will always trim brass to within a thousand of an inch or as close as we can get it to that. By doing so we achieve confidence that we have done our best to reload the most accurate ammo we can.

 

[PatMiles]

if you have space in front of your case mouth, lets say .030 so you say youll never have to trim right?, then you get a piece thats longer. you have carbon in that recess and you have .002 shoulder clearance (lets call it headspace to simplify) then as the firing pin drives the case forward the longer ones slam into that carbon ring where the shorter ones do not. we got people weighing primers and bullets to the .0001gn why would you possibly not trim your brass to all the same length? its mind boggling.

Dusty,
This is the type of info I was looking for, not just "I do" or "I don't" but understandable, comprehensive reasons to or not to.
Thanks,
Pat

 

[Dusty Stevens]

Dusty,
This is the type of info I was looking for, not just "I do" or "I don't" but understandable, comprehensive reasons to or not to.
Thanks,
Pat

You can take it as you will there pat. Always differing opinions. I just wanted to give an example of why instead of just saying yes or no to does it matter.

 

[BenPerfected]

You can take it as you will there pat. Always differing opinions. I just wanted to give an example of why instead of just saying yes or no to does it matter.

Maybe we could sum it up with....it is highly unlikely known

 

[dkhunt14]

What about cases that landed on the mouth on the bench or stones? Trimming and chamfering helps to make them nice again. I size my cases real hard and they grow about .005 every time. Matt

 

[LHSmith]

My chambers are so long in all of my BR rifles that I don't even waste my time trimming because they are not even close to the 10 thousands under chamber length that is recommended. To me it's the results you get on paper not what is speculation. I mean how is somebody going to prove that having your cases vary by 5 thousands that's it's going to shoot any different than if all your cases were cut exactly to the same length? Impossible. Like I said just speculation. Too many things going on during a match to nail down things like this to say where it matters or not.

Jack Neary believes so. He had someone hand him trimmed and untrimmed brass in a blind test and claims the target proved those with-in 0.003" variance were noticably smaller groups. See Neary rifle tuning part 1 on You Tube (at very end of vid)