Does a little difference in case length matter?

adamsgt

adamsgt

Jerry Adams
I decided to do a trial run of 15 cases to check out my process for prepping 6PPC brass. I measured the case length of the chamber at 1.535. After the first fire form with wax & pistol powder I measured the cases to trim to equal length which was 1.495. I wanted to trim before neck turning. Somewhere in setting up the Wilson trimmer I had a brain fart and ended up trimming to 1.480. Correcting my error, I prepped 50 pieces of brass, trimming to 1.495 length. Question, would that .015 make any real difference if I threw those shorter pieces of brass in with the rest? I don't know if I want to take .015 off the rest of the brass. I did screw up one piece of brass while neck turning and got it to .007 instead of .0085. I believe that would make a difference.
 
The shorter neck cases would have .015 less grip on the bullet than the longer ones. I'd think that would make a substantial difference in the release tension when firing. I'd just keep them sorted into the two groups and don't mix them on a target.

Jerry
 
adamsgt said:
I decided to do a trial run of 15 cases to check out my process for prepping 6PPC brass. I measured the case length of the chamber at 1.535. After the first fire form with wax & pistol powder I measured the cases to trim to equal length which was 1.495. I wanted to trim before neck turning. Somewhere in setting up the Wilson trimmer I had a brain fart and ended up trimming to 1.480. Correcting my error, I prepped 50 pieces of brass, trimming to 1.495 length. Question, would that .015 make any real difference if I threw those shorter pieces of brass in with the rest? I don't know if I want to take .015 off the rest of the brass. I did screw up one piece of brass while neck turning and got it to .007 instead of .0085. I believe that would make a difference.
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I have seen cases that were too long make one heck of a difference but never have seen any difference with cases .015 shorter than the others. While I would agree there are limits, when one considers the amount of boom that happend when the powder ignites and if one has a reasonable amount of bullet body in the case neck, I am of the opinion that in the course of a match, .015 won't be the difference between winning and loosing that match. They will grow soon enough if you use them. If you are concerned about the .015 use them for foulers for a time.
 
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Hmmmmmmm

I guess I've been thinking of neck tension as a function of only the neck diameter rather than a product of the diameter times the length. That would tie in with the concept of tweaking by varying seating depth. With the escalating cost of brass these days you can't afford to waste any. I guess I'll use the short ones for experimentation.
 
keep em seperate

JERRY...(admsgt)....keep the 15 shortys all by themselves (be shur and mark em with a auto center punch not just majic markr)....shoot those over and over and you will get into the rythm of a match and day of shooting....the main thing is shoot only brass that is the same at each target....dont mix em up....you will get vertical.....a fellow cut his match brass (alll of em) too short by a ton (.040-.050" I think) and won a major event with em.....they were all short,but,by the same ammount!!!!.....Roger
 
Everyone here knows that i am just a commoner, and my opinions dont carry much weight, but i have done a little testing here at home with ppc brass that varied in length as much as, but no more than .005 among ten pieces. I didn't see any difference when shooting the same brass with the same tuned load with the un-trimmed brass vs me trimming the brass to the same lengths all in the same bench session. I was just curious to see if i could tell any difference. With that said i do my best to keep my brass trimmed uniformly. Some one smarter than myself told me to keep my brass trimmed so i do! Lee
 
My experience with short brass is the carbon build up from the end of the neck to the reamed neck length. I'll bet you could never see the difference on paper. Another worry is cutting too far into the shoulder from a short neck. They do need to be the same length before turning.
 
I think it helps to keep them trimmed all the same. The fact that you asked the question means you will have some doubt if you don't keep them trimmed. I didn;t think it would matter much and then started to notice that i seemed to shoot better after they were all trimmed. I can't prove it, but my experience tells me to trim often when i really want to shoot well.
 
With guys like Jack and Lou recommend trimming, I'd listen to them. They both have the ability and facilities available to test whether it makes a difference or not.
 
Wait a minute, I was under the impression that if you have your reamer set up with a bunch of magical radiuses, and you have dies that are made from magical pixie metal, you would never have to trim in the first place??:confused: You mean to tell me that all these smart folks haven't figured this out already?:rolleyes:;)
 
In my limited experience I find it pretty tough to find Virgin Lapua brass that can be trimmed longer than 1.500" before turning. I guess I may have not checked in a while but that is the standard I use. After fire forming it is pretty close to 1.490". Maybe 1.492-1.493. I trim them back to 1.490 and that is where I keep them. I got into the routine of trimming after each day of shooting. I have noticed that they do not grow a whole lot keping them at that length.

I would do it after each yardage but I am to anal with my reloading habits that it would be another half hour before I got to the line after lunch break.
 
Calvin for me the last 2 boxes have not been longer than 1.4820 after fire forming. Admittedly they were from the same lot.
All during last year I could not get them to grow where I could trim them longer than 1.485.
Year before last it was hard to keep them trimmed short enough. These last 2 boxes were blue and 2 years ago it was gold.
 
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