How critical in case trimming??

[Gmac]

So I’m reloading 308 w Hornady 168 ELD, mostly for target shooting w RPR. I trim cases back to abt 2.010 w Lyman manual trimmer but get some variance: maybe 2.008-2.012. I don’t want to be neurotic about this. Can someone tell me important is case length when trimming? I know COL is important and I have a micrometer-head bullet seater for that but what abt case trimming? Thnx for advice.

 

[CK1.0]

Ultimately, the lower the variance, the better… this pretty much goes for everything related to reloading.

In a perfect world every round we made would be exactly like and a perfect clone of the last one and the next one…

If you’re already at a net SD of 0 in all other aspects, then your targets will tell you how much your variance in trim length matters.

 

[rijndael]

maybe 2.008-2.012.

IMO, you're fine. I've seen more variation in Lapua brass, out of the blue box. It shot pretty darn good.

 

[918v]

you’re good

 

[straightshooter1]

So I’m reloading 308 w Hornady 168 ELD, mostly for target shooting w RPR. I trim cases back to abt 2.010 w Lyman manual trimmer but get some variance: maybe 2.008-2.012. I don’t want to be neurotic about this. Can someone tell me important is case length when trimming? I know COL is important and I have a micrometer-head bullet seater for that but what abt case trimming? Thnx for advice.

There are two main issues, as I see it. You have the max SAAMI case length of 2.015 where you don't want to bump into the 2nd shoulder with the case mouth, which can cause a significant pressure spike when done. And second, there's the issue with the carbon ring build up, where you don't what you case mouth binding on it as that too can cause a significant pressure spike.

If you have a SAAMI spec chamber, you're 2.008-2.012" is short enough to cause no problem. However, when sizing the brass the case length/neck grows and often can grow as much as .003 where you're 2.012" could be bumping into that 2nd shoulder if you don't trim them after sizing. So, you're case lengths, it's a good idea to trim after every FL sizing.

If you're not cleaning out the carbon ring when cleaning your gun and not trimming the cases after every firing, you'll run into the same issue as with the 2nd shoulder as that carbon ring builds up.

Otherwise, some "variance" as you've have is not really a big deal if precision shooting is not what you're doing. Precision shooters, on the other hand, want everything to be as consistent as possible in order to shoot tiny, tiny groups at long range.

For my .308, I trim to 2.007 with a 3-way trimmer, which gives me a variance if .001 or less as well as consistent and square chamfers. And I trim every time I process my brass for that consistency, which I figure avoids the issue with any carbon ring build up.

 

[zeroz]

You're good. Doubtful you'll see .003 case length on target. Doubtful you'll see it on a chrony or have logged enough data and have tight enough tolerances on everything else to know that's the absolute culprit. Some guys may but they get so far in the weeds loading that they can't sleep at night. If you're doing 1000yd benchrest it may be an evil you need bare, for steel, load and send.

I trim back to 2.006-8 after about every 3 firings or when it starts creeping up on 2.015. If I had to trim after every firing I'd quit loading. Its the worst.

 

[Gohring65]

If your trimmer is grabbing the brass by the rim on the case head with a shell holder that is most likely your variance.
I wouldn’t sweat it.

 

[Haney]

Uniform length is a good thing , but you don't now how your brass compares to your chamber . With a gauge like this you may find some rifles will never need trimming other than to uniform them . I have many rifles there is no way my brass will ever grow long enough to matter . Short brass can lead to all kinds of bad things .

https://www.sinclairintl.com/reload...s/sinclair-chamber-length-gage-prod32925.aspx

 

[rydah]

I used to trim, chamfer and deburr every firing. But with this new barrel I haven’t trimmed once. I put a chamfer on the virgin brass and that’s it and this barrel has been the best shooting barrel/load I’ve had in a while. I have about 5 thou of variance and 4 firings on them. Once they grow to trim length I’ll trim them back to min but that’s it. I’m slowly experimenting/trying to stop doing things that don’t matter to save time and make loading quicker and easier and this seems like one of them I can cross off the list.

6GT
Lothar Walther 1-7.5 twist 24 inch
Alpha ocd brass bumped 1 thou and 2 thou neck tension
110gr atips 30 thou off lands
31.9gr h4895 2835fps
Cci br4 primers