Case Trim Length

[welscher663]

Question on lapua brass trim length for 6br.. I measure numerous cases and come out with most all of them coming in under what is considered "trim length", but their not consistent (maybe a few thousandths difference)

what i'm wondering is does a person pick a few (.005-.007) or so below " recommended trim length" and trim all your cases to that length being as you trim them as long as your supposed to?

Thanks in advance, I just want to make sure i'm doing it right and not losing accuracy

 

[rmist]

I don't trim any until after the 1st firing. I also don't clean up primer pockets until after the 1st firing as well. They'll grow and move a little and then trim all to the shortest case if it's at or above the minimum case length. Never had any issues after that. Accuracy doesn't fall off much with the untrimmed cases.

 

[Shynloco]

Personally, I keep all my brass trimmed to the recommended case length. Any of the shorter one's I use as "fouler brass." In all the books I've read about "accuracy shooting," the admonishment has always been, "what you do to one, you do to all." In short, keep them uniform and as even as humanly possible. And buy a good trimmer that assists in that effort. The cheaper ones work against you in this category.

Alex

 

[Sniper338]

I measure them all.. then trim to the shorest one... its usually only a few thou... dont hurt anything and its piece of mind... i use the wilson trimmer... it cuts to 1 thou perfectly the same across the board..

then i write down that trim length and stick to it for that rifle and all the other brass i get too... keep em all the same!

 

[Ackman]

Unless your chamber was cut with a reamer spec'd to the brass, new cases are much shorter than a chamber anyway. And the Lapua brass I have is all very uniform at about trim length which makes it shorter than you'd want it to be anyway.
Before you go trimming everything try this. With your accuracy load do a test..........several groups with brass trimmed and several groups with untrimmed brass of slightly different lengths. You won't see any difference.

 

[LHSmith]

^^^^^ Watch Jack Neary's dissertation on "Tuning the 6PPC" on Youtube. He addresses trim length, and finds that it does show up on the target (i.e. consistent length's = smaller groups). After seeing this video, and since then maintaining a 0.002" max. variation in case length, I concur.

 

[amamnn]

+ 1 for trim to the shortest case---unless it is ridiculously short--for what it's worth - this works for me.

I trim after the first FL sizing--which is always the second thing out of the box. The first is primer pocket uniforming. I have found that unless you are running really hot loads, the pocket changes little or not at all as measured with the K&M dial indicator primer pocket measure and seater tool. Some people like to load a crazy hot FF load and they might have some movement in the pocket, but I don't feel comfortable with such loads and do my FF in 2 stages. I check case length after every second firing for most cases--.22BR and .243 WSSM are exceptions I look at them every time. I find that my cases may possibly have a tiny bit of brass to be removed from the pocket about the same time I need to trim case length. Since my cases after FF are well matched to the chamber and the dies to the chamber, I do not do a lot of heavy resizing even with cases I FL size only.

I know folks who compete will run with a batch of brass all season and not do anything to it except trim length-- maybe--but I am able to take the time to fool with my brass for my various experiments....... also + 1 as pertains to Jack Neary's sessions-- a lot more info is imparted there than just this.

 

[Ackman]

^^^^^ Watch Jack Neary's dissertation on "Tuning the 6PPC" on Youtube. He addresses trim length, and finds that it does show up on the target (i.e. consistent length's = smaller groups). After seeing this video, and since then maintaining a 0.002" max. variation in case length, I concur.

First off, benchrest is the most anal of disciplines. But unless someone has a $3000 target rifle (or whatever they cost now) and can actually shoot consistently enough, then be able measure accurately thousandths of an inch difference in group size........you won't see any accuracy difference in brass that's trimmed or has a couple thou variation in length. But if the OP....welscher....really wants to find out how it applies to his situation, he should do his own test and make his own judgement.

 

[LHSmith]

But if the OP....welscher....really wants to find out how it applies to his situation, he should do his own test and make his own judgement.

Agreed. However, we usually do not know the OP's skill level or accuracy potential of their equipment. Also, other readers of these threads may indeed possess both the skills and the equipment that some of these "anal" BR practices might improve their accuracy.I simply disagreed with your blanket statement that trim length does not affect accuracy. In fact anything you do to minimize variables, will instill a lot of confidence in your equipment...and confidence can take you a long way.

 

[jcampbellsmith]

For each calibre I have a nominal case length. I measure the case, if it's longer than the nominal length I trim it. If it's shorter I do nothing.

Regards

JCS

 

[Ackman]

But if the OP....welscher....really wants to find out how it applies to his situation, he should do his own test and make his own judgement.

Agreed. However, we usually do not know the OP's skill level or accuracy potential of their equipment. Also, other readers of these threads may indeed possess both the skills and the equipment that some of these "anal" BR practices might improve their accuracy. I simply disagreed with your blanket statement that trim length does not affect accuracy. In fact anything you do to minimize variables, will instill a lot of confidence in your equipment...and confidence can take you a long way.

You can believe whatever you wish, people do it all the time. They believe whatever makes them feel better about something. Shooters are especially gullible when it comes to what they think is gonna' make that gun reeeally accurate and grab onto "accuracy" buzzwords....... "casetrimming" is one of them. If you're a benchrest shooter then you do everything you can think of that might gain anything, even if it's nothing, even if reading the wind is more important than all of them put together. One friend was a hardcore br shooter for many years. Being the very fussy perfectionist he is, in his ppc he tested the myth of accuracy loss when every case wasn't trimmed to exactly the same length and found it to be just that, a myth.

Regarding welscher's post about Lapua 6BR brass......I have tons of gold box Lapua 6BR brass, somewhere around 1500 pieces, and so have measured many piles of them out of curiosity more than anything else. They're fanatically uniform. Most are exactly the same length. The very few that aren't, vary by never more than .001" in length. Their .223 brass is the same. Dakota Lapua, same thing. The stuff just doesn't need "trimming to length"

 

[LHSmith]

^^^^^ Actually, Jack Neary who is a HOF shooter,tends to be super-anal on his test procedures. In the evaluation on case length affects, he conducted the test blind( like many of his test trials)i.e. someone handed him cases from 2 lots, one trimmed, and the other lot with variable over-all lengths.
The need to maintain consistent case lengths is also supported in books written by 3 other BR HOF members, Boyer, Newick, and Ratigan. Since my experience, and that of some very successful fellow competitors mirrors the author's findings, I side with the "it is fact crowd".
In a factory gun with factory chamber, most likely you won't see a difference....not even in a Sako 6 PPC.

 

[Jet]

Like LHSmith said above, minimizing variables is critical to success.

If you have the time and tools to perform this task, you should.

 

[welscher663]

Appreciate the advice, I believe I will go ahead and trim to shortest case, I can use all of the help I can get accuracy wise. I've got a high end trimmer, so that is no problem. Hopefully this will bring the groups in a little more.. but I believe practice is my best friend at this point in time!

 

[Brians356]

then i write down that trim length and stick to it for that rifle and all the other brass i get too... keep em all the same!

So, once you even them all up, you the trim every case after every firing to keep them all the same? (Assuming a case length will always change measurably every firing. Since most reloaders list "trimming cases" as their least enjoyable activity, that seems like dedication, indeed!)