308 Case Length


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tkcomer
October 6, 2006, 04:41 PM
Ok, I just got these dies in. I set up the size die per the RCBS instructions and full length sized the case. I then used a Lee trimmer (The one that chucks up in a drill) to trim the case. My old Lyman caliper is showing the case length to be around 2.09. My Sierra book shows case length to be 2.015 and the IMR site shows a case length of 2.005. Are these minimum lengths? The case is some sort of nickel plated tactical round the police use. Once fired. Its marked 308 WIN on the bottom and has a FC stamp on the top. The empty re-sized case chambers in the rifle with no difficulty. The Lee trimmer did take off some metal when I chucked it up in the drill, but Im wondering, is the 2.09 length too long? Or am I being paranoid again?

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db_tanker
October 6, 2006, 04:58 PM
Trim to length is 2.005

Max length is 2.015

Also that nickel case is going to be a bit rough on your dies so use a good lube.

D

tkcomer
October 6, 2006, 05:13 PM
Crap. The once fired cases are pretty consistent at around 2.11. I chucked the case back into the Lee trimmer, but no more comes off. Still at 2.09. I use the RCBS lube. The only case Ive sized so far went through pretty easy. Pulling it back out was tough though.

ocabj
October 6, 2006, 05:35 PM
2.005 or 2.015, it doesn't really matter. All that really matters is that you trim the brass in each lot to the same length. Consistency is the key to accuracy.

tkcomer
October 6, 2006, 06:22 PM
So 2.09” is OK? It chambers in the rifle fine. No hint of any interference. I plan to trim all cases with the Lee trimmer.

P0832177
October 7, 2006, 12:19 AM
Unless you do a chamber cast of your chamber, you will have to rely on the suggest case lengths.

Max lenght 2.015 with a trim to 2.005. So anything less then 2.015 should work for you.

Matt-man
October 7, 2006, 02:50 AM
So 2.09 is OK?

NO! If your case neck is too long it's possible that it won't be able to expand properly to release the bullet upon firing, and that results in a high pressure situation. Unless you've measured your chamber and know for sure what length you can use, I strongly recommend you stick with the SAAMI lengths!

Just so that we're all on the same page here, 2.09" is .075" over the SAAMI max case length of 2.015".

Geeko
October 7, 2006, 08:03 AM
Trimming to SAMMI min 2.005 works well. I have measured NIB, never loaded/fired LC Match cases and they are all trimmed to 2.004-2.005. The one issue you may want to look into is the setting of your sizing die. I also followed RCBS instructions and found that those instructions work fine for ANY 308 chamber. The shoulder was being bumped or set back so far that headspacing was never a problem. After, measuring the headspace on my rifle, I reset the resizing die. The die is no longer touching the shellholder plus the 1/8 to 1/4 more turn down as RCBS says to do.

tkcomer
October 7, 2006, 09:19 AM
Well, double crap. I have a caliper problem. There is a bad spot in the teeth. Best I can tell, it seems to be in the 2.01 range + or a little. So Im pretty close, but Ill not load a shell until I get a new set of calipers in. I even have a stainless caliper, but something is wrong with it too. I cant even get that to repeat zero. Sorry for the trouble. Its been a long time since Ive used this stuff.

Geeko
October 7, 2006, 01:14 PM
One very useful tool is the RCBS Preicision Mic. It measures the headspace of the cases either unloaded or loaded. Zero on it is suppose to be 1.630 SAMMI min. I tried the Stoney Point too, but I liked the Mic better. The Stoney gave me weird info using their .400 adapter for the 308/3006 shoulder. The tolerances looked to be stacking up against me. Tolerances of the caliber and tolerances of the Stoney. With the RCBS mic there is only the tolerance of the one tool, not the additive effect.

tkcomer
October 7, 2006, 01:44 PM
Im still trying to make up my mind if I want the dial or digital calipers. The digital looks kind fragile.

db_tanker
October 7, 2006, 03:58 PM
Mitutoyo or Starret Digital calipers aren't too fragile...

I work at Baker Hughes and we use those brands as well as Browne & Sharpe and all work VERY well...I prefer dial and vernier calipers but most call me a throw-back. :D


D

USSR
October 7, 2006, 07:30 PM
tkcomer,

You seem to be dropping a zero when you are giving the length of your case. You mean your once-fired length is 2.009, not 2.09 correct? In any case, ocabj is correct, as long as they are below the SAAMI maximum length, it doesn't matter what the length is as long as they are all that length for consistancy. Personally, I would trim them all to the length of your shortest case.

Don

tkcomer
October 7, 2006, 08:17 PM
Like I said, Im using the Lee case trimmer after I resize and clean the cases. My calipers are crap. If I pull the one caliper out real slow, it seems to show a case size of around 2.01 + or just a little. Looks like Im between 2.009 and 2.012. If I pull the caliper out quick, it seems like its skipping a few teeth right at the very beginning. Ive pitched the other caliper in the trash. Im kinda interested in the RCBS precision mic gauge. But since Ive resized all my (few) brass, I assume I would use it the next time I reload.

Poper
October 9, 2006, 11:34 AM
tk,
I have the RCBS Precision Mic's for all rifle calibers I reload for except .260 Remington (they don't make one for that yet). These tools will provide the means to acquire headspace dimensions and bullet seating depth in relation to the chamber throat/lands. The PM will allow you to precisely set your sizing die so that you do not set the shoulder back too far and create an excessive headspace condition. It will also minimize the working of the brass and help extend case life.
However, a quality dial caliper is mandatory for all case/cartridge length measurements.
Personally, I have found the Precision Mic's easy to use with repeatable accuracy. I find them well worth the investment.

Yes, 2.09" is too long. However, if you are misreading the measurement or tyop-ing it and it is really 2.009", then your measured dimension is in the middle range of the tollerances for case length and are ok. (I.E. 2.015 max., 2.005 trim-to.)

I hope this is helpful.

Poper

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