.308 case length


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hvychev77
July 27, 2014, 08:19 PM
I resized and primed 100 federal cases today for my. 308 and then primed them. The problem is that I found a few pieces that were at 2.018-2.019" after the fact. I know that max case length is supposed to be at 2.015". So, I chambered the longest piece in my rifle and it was really easy to close the bolt. Is this an issue to be concerned about? How will this affect accuracy? Thanks. Hvychev77

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Walkalong
July 27, 2014, 08:28 PM
Accuracy is about consistency. Always trim after sizing.

Another issue is that while they chambered in that rifle OK, or at least they seemed to, they may not in another and cause excessive pressures if fired.

hvychev77
July 27, 2014, 08:43 PM
Well if they chamber in my gun are they safe to shoot? Also, can you trim after they have been primed? I will only shoot these in my gun, I do not share my reloads.....i'm greedy like that!! lol

catgunguy
July 27, 2014, 08:54 PM
I don't know why you would not be able to trim your brass with the primers in them. I use a Forster trimmer and there is nothing that would come near the primmer while trimming.

rcmodel
July 27, 2014, 08:57 PM
Yes.
You can trim them after priming with a 'normal' hand crank, lathe type case trimmer.

No.
You can't trim them with a Lee Case Trimmer because the depth stop pin has to do through the flash hole of the case.

rc

hvychev77
July 27, 2014, 09:13 PM
Thanks guys. I'm planning on ordering a RCBS pro trimmer tomorrow. Feel free to suggest others that you would recommend using. Thanks again.

Cheesemaker
July 27, 2014, 09:22 PM
I use Hornady's "hand crank" trimmer - works well enough. I doubt you can go wrong with RCBS or other major brand. Don't forget to deburr and chamfer after trimming - trimming can leave the mouth a bit "ragged".
I echo Walkalong - it's all about consistency and case length is one of the variables that need to be dealt with.
I trim to 2.005 when they hit 2.014+
Good luck.

SlamFire1
July 27, 2014, 09:37 PM
Over length cases can be chambered, and will cause pressure problems. Too long is much worse than too short, in fact, too short has not been a problem at all for me. In setting up trimmers, I have trimmed cases well below the “minimum” and as long as the case neck can hold the bullet, the round went bang. But, too long, early in my reloading experience I had too long of case necks in 30-06 cartridges and I blew primers. The case neck was being pinched in the throat, but I could not tell because spring tension and the seven to one leverages found in bolt rifles hide any symptoms of an interference fit.

I trim my 308 cases to 2.00” and don’t sweat it if they are 1.995”.

Anyone who can see accuracy differences with trim lengths is either shooting a bench rest rifle, or is making accuracy claims on very small sample sizes. These sort of effects are in the noise level.

Walkalong
July 27, 2014, 10:59 PM
A great many things have a great deal more affect on accuracy on target than a .005 difference in cases, that's for sure.

Sounded like the OP had cases from 2.005 to 2.015. Simply no need to have them vary that much, so why settle for it, not to mention they could be too long for the chamber.

As posted, a bolt gun can squeeze a round into the chamber that can be tight in the throat area due to an overly long case, hence my "or at least they seemed to" comment.

"a bench rest rifle (http://www.thehighroad.org/attachment.php?attachmentid=111387&d=1261261610)" :)

gamestalker
July 28, 2014, 02:17 AM
Trimmed length has nothing to do with head space of the brass to your chamber. Let me elaborate a bit here.

The maximum case length as determined by SAAMI spec is about the length of the neck. If a case exceeds the max. SAAMI length, what can happen is, when it has a bullet seated in it, is chambered and fired, the mouth extends to far into the throat, and when the cartridge is fired the mouth must be able to expand to release the bullet. If the neck is too long, it becomes pinched, the result can be extreme pressures, very extreme. This is the entire reason for SAAMI spec relating to trim too lengths, and maximum case length. Although a case that is in need of trimming may easily chamber in multiple rifles, it may not be safe to be fired if it exceeds the max length. This particular element of reloading is completely, and totally controlled by trimming and unrelated to resizing.

Head space of the brass, which is the distance from the case head, to the shoulder in relation to the dimensions of the rifle, from bolt face to shoulder datum. This is what effects cartridge fit in a particular rifle and is adjusted by how much one pushes / bumps the shoulder back during resizing, and it has absolutely nothing to do with brass trim length.

GS

hvychev77
July 28, 2014, 06:22 PM
Gamestalker, thanks for the descriptive explaination. To be honest, I've never had to trim cases before and never looked into the good and bad of NOT trimming. Definitely some danger there. Again, thanks for all the replies, help, and education.

grubbylabs
July 28, 2014, 07:12 PM
If you trim a lot of cases based on the 308 family of cases like 243 to name another, look into getting a WFT trimmer. I only have two of them, one for 223 and one for 308, but I also load those for semi auto's, so I wind up doing a lot of case prep.

stubbicatt
July 29, 2014, 12:10 PM
I like the WFT that I bought from Midway for my 308. You can trim with it after you have primed the cases, and it does a good job.

Trimming is my least favorite aspect of reloading. I have tried many trimmers, powered and hand cranked, and for the money spent it is my opinion that the WFT is a good alternative.

I find that trimming to the "trim to length" which IIRC is 2.005" on the 308 is the best for factory rifles. In the case of a custom chamber, I use the Sinclair OAL finder plug that will determine the maximum overall length of your chamber, so you can trim your cases to the proper length for a given chamber.

Good luck.

FLIGHT762
July 29, 2014, 05:14 PM
I used to be very anal over trimming my 308 cases to under 2.015" for my two target bolt guns. One rifle is a factory gun the other a custom barrel.

I finally bought a Sinclair chamber length gauge. What I found was my factory barrel had a chamber length of 2.045" and the custom barrel had a chamber length of 2.040". I actually laughed when I confirmed the lengths. I don't worry about it so much anymore if a case gets a bit over 2.015".

243winxb
July 29, 2014, 08:02 PM
Some head to datum measurements may become shorter (shoulder pushed back) from chambering in auto loaders or from the strike of the firing pin. This will have the same effect as a longer trim length. There is a "safety zone" built into the chamber, so this is not a problem when trimming brass correctly. But unless you take measurement, you do not know your true chamber length. Dont let your trim length exceed maximum length for safety. Primers must be removed to use a Lyman universal case trimmer.

pseudonymity
July 29, 2014, 10:27 PM
Not directly related to case length, but to Federal cases in .308 specifically. If you have not worked up loads in Federal .308 brass, use caution in using load data from other cases. Federal brass can have as much as 2g less capacity than other cases like RP, Winchester, etc. Mild loads in Win brass can have you pounding the bolt open when loaded in Federal brass.

gamestalker
July 30, 2014, 01:14 AM
When measuring a chamber, that measurements doesn't always reflect where the neck would become constricted if the brass is beyond the SAAMI max.. In other words, where the olgive of a bullet may engage the rifling, is not the same as where the throat begins to narrow, this is what causes mouths to become constricted or pinched when the brass exceeds SAAMI max length, two different points of contact.

GS

243winxb
July 30, 2014, 08:54 AM
Sinclair Chamber Length Gage http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx http://i338.photobucket.com/albums/n420/joe1944usa/FirearmsReloading102/FindingCOL.jpg

Jim Watson
July 30, 2014, 09:10 AM
I agree with Flight, the actual chamber neck length is not likely to be at the SAAMI standard, most are longer. If you want a personalized trim length, the gauge is not expensive, $5.99 at Sinclair International.

People read about target ammo loading and are mystified when they find throats so long they cannot load bullets close to the lands and have them fit the magazine, or even seat securely for their factory rifle. They don't see much from neck turning because the chamber neck is too large to start with. Same deal on trimming. You probably need to trim but the question is, how much? Cutting to the handbook recommendation of .010" under SAAMI is safe.

243winxb
July 30, 2014, 09:14 AM
I agree with Flight. +1 The gauge would be a waste of $. IMO.

BillB204
July 31, 2014, 08:01 AM
Please correct me if I'm wrong. I reload .308 for an AR-10. The neck gets no where near the chamber mouth. Safety should not be a concern. But I still trim to 2.005. When the cases expand to 2.010, I trim back to 2.005. My reason for doing this is for long distance accuracy. I've not chrony'd to verify this; but it seems that additional neck length is going to hold the bullet just a bit stronger. This could affect pressure that could then affect MV that could then affect ES. Probably wouldn't affect short distance accuracy. By I believe it could affect 600+ yard accuracy. I'm a BR shooter so I guess I'm a bit OC when it comes to absolute consistency in reloading. Am I off?

243winxb
July 31, 2014, 10:02 AM
.308 for an AR-10. Check to see how much the bullet moves on chambering. You may find you need all the neck tension you can get. http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm While your testing, check for shoulder set back (head to datum) from chambering.

BillB204
July 31, 2014, 10:58 AM
Check to see how much the bullet moves on chambering. You may find you need all the neck tension you can get. http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm While your testing, check for shoulder set back (head to datum) from chambering.
I've checked both. Even at 2.005 the neck is tight enough that the oal doesn't change after chambering. And I suppose because the chamber is so long, I'm not getting any change in the shoulder.

243winxb
July 31, 2014, 01:04 PM
Just asked about the shoulder because of this thread.. http://thefiringline.com/forums/showthread.php?t=549747

BillB204
July 31, 2014, 02:26 PM
Just asked about the shoulder because of this thread.. http://thefiringline.com/forums/showthread.php?t=549747
Wow! Interesting thread. Thanks. A lot of great info and great theories. I'll have to read it a few more times to fully absorb. I'll be going home and doing some more testing of my own.

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