Trimming brass to same length?

[LHSmith]

FWIW, Jack Neary has a Precision Shooter Gold jacket earned back in "05. To date he has 116 Precision rifleman points. Unless someone that has achieved more success in the game disproves Jack's findings.......when Neary speaks I will listen (and take notes)

 

[PatMiles]

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.

I appreciate it sir.

 

[suasponte]

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.

Add to that guys that never clean the chamber!

 

[suasponte]

Post I just did on tracking brass lengths with New bluetooth calipers into Excel on my phone. Fast and eliminates having to write it down. Just places your brass in the loading blocks and your ammo box per how the rows are in the excel file.
http://forum.accurateshooter.com/th...liper-bluetooth-case-length-checking.3948462/
Terry

 

[PatMiles]

FWIW, Jack Neary has a Precision Shooter Gold jacket earned back in "05. To date he has 116 Precision rifleman points. Unless someone that has achieved more success in the game disproves Jack's findings.......when Neary speaks I will listen (and take notes)

And probably buy him dinner too.

 

[dkhunt14]

Who cares about Precision rifleman points Matt, I certainly don't, and I don't give a rat's ass what people think of me. Do you think I care? After what happened last year with the decision the IBS made I could care less about competing anymore because the IBS can't follow their own rulebook. The IBS is a joke. I just can't believe that someone makes a statement like having 2 thousands difference in neck length is going to make a difference. That's horse shit. Everyone talks about how you have to do this or that but nobody can prove without a doubt that doing all this little shit is going to automatically small groups. Like I said it's all speculation. When the wind is blowing 25MPH do you think that uniform neck length is going to matter? Get real man!

Maybe at 100 yards, it doesn't matter. But the things we do at 1000 matters alot more. Ask your short range buddies like Bart, Roger Gower, Chuck and a bunch of others. They find out real quick that what worked for them at short range doesn't work at long range. Matt

 

[muleman69]

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 .

You are correct ,for me every little bit helps and I never want to miss a step whether right or wrong. I'm also a believer in if it works for you, by all means run with it.

 

[LHSmith]

Who cares about Precision rifleman points Matt, I certainly don't, and I don't give a rat's ass what people think of me. Do you think I care? I just can't believe that someone makes a statement like having 2 thousands difference in neck length is going to make a difference. That's horse shit. Everyone talks about how you have to do this or that but nobody can prove without a doubt that doing all this little shit is going to automatically small groups. Like I said it's all speculation. When the wind is blowing 25MPH do you think that uniform neck length is going to matter? Get real man!

#1-Allie's got several decades of competition over Jack.......Allie shoots both group and score....hence the opportunity to garner more points
#2- I learned a long time ago that what fellow competitors tell you they do and what they actually do should be looked at with skepticism. And why should they disclose their regimen? They did all the hard work to get where they are.
#3- If you would have reviewed the vid- Jack said the difference could be seen on an "honest" day at 100 and 200 yds.
#4- Discrediting well known successful shooters who go out of their way to teach what they have learned in years of competition is not going to win you many friends.
#5- Keeping brass length with-in 0.002" is a pretty simple task. And it abides the #1 rule in BR-"minimize as many variables as possible" so what's to argue against that?

 

[Bruce W]

I believe its noted in the Jack Neary video to trim regularly. i dont remember if there was any reasoning layed down in that presentation. Also page 156 of Tony Boyers book on rifle accuracy points out that the uneven length (longer reacts with carbon rings and is noted as a possible source for fliers . Bruce

 

[Dusty Stevens]

Also page 156 of Tony Boyers book on rifle accuracy points out that the uneven length (longer reacts with carbon rings and is noted as a possible source for fliers . Bruce

Exactly

 

[Ringostar]

Here is another view point. I neck turn my competition brass. My neck turner indexes off of the case mouth. Therefore I trim to equal length, so that I get a consistent depth of turn down to the shoulder.

 

[ClassCat]

I believe its noted in the Jack Neary video to trim regularly. i dont remember if there was any reasoning layed down in that presentation. Also page 156 of Tony Boyers book on rifle accuracy points out that the uneven length (longer reacts with carbon rings and is noted as a possible source for fliers . Bruce

Shorter length also creates carbon rings. It's all how you maintain (Eliminate ) them

 

[hikfromstik]

Prove it that if one neck is 2 thousands longer than another one that it's going to make any difference at all as far as releasing a bullet any different. There is no way your going to tell me that this is true. Just speculation on your part.

2 thousands is probably no deal breaker , but 4 or 5 thousand and you may see a difference . You probably can't prove that 2 thousands won't make a difference on shoulder bump , but I would rather be safe and have confidence in my work than to take chances .

 

[hikfromstik]

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?

I have not of a clue ,lol Too many variables like neck tension , perfectly rounded necks , bullet material .

 

[Bart B.]

I have not of a clue ,lol Too many variables like neck tension , perfectly rounded necks , bullet material .

All the variables add up to requiring 10 pounds of force to push the bullet in the case neck. Adding .005" more neck grip increases the neck grip area 2%. So, 2% more force is required.

Originally, about 134 psi would be needed. 2% more force needed requires almost 137 psi.

30 caliber bullets have about .0745 square inch area, a bit more than 1/13th square inch. 10 pounds force is about 1/13th of 134.2 psi. Formula for force on bullet = psi X bullet cross section area

 

[Forum Boss]

Here is another view point. I neck turn my competition brass. My neck turner indexes off of the case mouth. Therefore I trim to equal length, so that I get a consistent depth of turn down to the shoulder.

He is absolutely right. If you neck turn, with almost any tool on the market, you will need consistent neck lengths.

Another reason. You can get a more consistent (every case the same) inside/outside chamfer with brass that has recently had expander mandrel run in neck and been recently trimmed (so the casemouth edges are all uniform). Our tests definitely show lower ES/SD with brass that has been uniformed in every respect, though that will include neck turning and chamfering so it is difficult to isolate neck length as source of lower ES. No question lower ES will shoot tighter groups at 600 yards and beyond.

 

[Brians356]

Here is another view point. I neck turn my competition brass. My neck turner indexes off of the case mouth. Therefore I trim to equal length, so that I get a consistent depth of turn down to the shoulder.

I'm with you, but for that to work well your neck trimmer must index off the shoulder. Does yours?
-

 

[Brians356]

He is absolutely right. If you neck turn, with almost any tool on the market, you will need consistent neck lengths.

I agree 100% But to get consistent neck lengths (not necessarily case lengths) the trimmer needs to index off the shoulder, not the case's base.
-

 

[Campbell]

OK, folks

What is your acceptable tolerance of case trimming length?

I find it difficult to get within .001.

What I don't understand (being a mere accountant, rather than an engineer) is why! I set up the RCBS trimmer so that the first case is bob-on, yet subsequent case may vary. My recent thought is that tiny amounts of bras swarf gets behind the base of the case and the trimmer's jaw, causing the case length to get altered. Answers on a post card, please!!!

 

[jimmymac]

I'm with you, but for that to work well your neck trimmer must index off the shoulder. Does yours?
-

Doesn't running the virgin brass through a sizer die prior to trimming solve this?

Size, trim, then neck turn. That's how I was taught to do it.