308 case trimming

[SavageShooter2k]

I have a Savage short action in 308 that i have been hand loading for a few years now with great results. I have a great pet load that I have used for long range shooting and I have kept the ingredients the same for it over the years. Same brass, same primers, same bullet, powder,etc.

Recently I land some really nice once fired Federal brass and I am now looking to put some it to use as some of my PPU brass is starting to fall apart. I have been using PPU for this load exclusively with great success.

So I cleaned and sized up this brass and I am noticing it is longer than my PPU brass. Oddly all of my PPU brass has kept its length really well with no need for trimming to this point. Even after several loading the case length has stayed in the 2.010-2.015 range. This Federal brass has come in at 2.020 which is longer than the maximum recommended case length.

Do you guys think I desperately need to trim or can I just run with it without seeing any problems?

Thanks for the input.

 

[Da Yooper]

Personally i would trim. I always trim but that is just me.

 

[NuJudge]

A lot of chambers can accept longer than max length brass, but the only way to find out is doing a chamber cast. If you load longer than standard brass, and you have a chamber that is standard, bad things happen, especially pressure spikes.

 

[25-5]

Brass longer than the max in the manual needs to be trimmed.
I like the Lyman trimmer. You can crank by hand or get the drill attachment.
If you do large amounts, as I do for the M1A, I would suggest the "Trim-It". YouTube has videos on it. I like it the best. It's quickest and aids the ream/chamfer step.
If you choose the Lyman get the carbide bits.

 

[SavageShooter2k]

Thanks for the input guys, I am going to go ahead and trim it. I have a hornady case trimmer but I dont have a shell holder that fits in the trimmer for my .308 so I will just have to buy one. Better safe than sorry and it may have a slight effect on accuracy so why not.

 

[JohnhenrySTL]

I have to trim pretty much every cycle. How many times have you shot them so far? And if you don't mind me asking what is your load? I have not had good luck with ppu brass. I've had neck and mouth splits.

 

[Reloadron]

I check my brass after each firing and trim to 2.005 as required. However, I only bother to do that because I want uniformity in my hand loads. SAAMI cartridge dimensions for the 308 Winchester is a cartridge Max length of 2.015" - .020" so anywhere between 1.995" and 2.015" is within acceptable limits. Minimum chamber is 2.025". On my 308 loads they end up in any of several rifles so I just try to make them all the same. Do they need trimmed every loading? Nope. Not as long as they are within specifications.

Just My Take....
Ron

 

[lysanderxiii]

If you taper crimp, you need to trim.

 

[Walkalong]

Trim every time, lightly deburr & chamfer.

 

[SavageShooter2k]

I have to trim pretty much every cycle. How many times have you shot them so far? And if you don't mind me asking what is your load? I have not had good luck with ppu brass. I've had neck and mouth splits.

It's 44 grains varget and a 178 hornady bthp 2.805 oal. Shoots 3/4 MOA out to 600 with ease at 2630 fps out of my 20" barrel. I am getting 4-5 reloads out of each piece of ppu brass.

 

[gamestalker]

Some things to consider.

I wasn't completely clear on when you are measuring and trimming?

First of all, If you are measuring before resizing, you aren't getting the true case length, or the case length that matters. Case head to mouth length will always be longer after being resized. Which is why we measure and trim only after resizing,

And if you use brass that exceeds SAAMI maximum after it's been resized, there is a serious risk of experiencing some very excessive pressures. What happens when the case mouth gets into the throat, is it gets restricted, pinched when the cartridge is fired. This is because it can't fully expand to release the bullet, this slight restriction can indeed produce some very significant pressure spikes.

GS

 

[Bart B.]

I trim my .308 cases to 2.000" and not again until they're almost 2.015". I see no accuracy problems with that much spread in case length.

How much spread in neck grip on a bullet have with a .010" spread in neck length have? How do you measure it precisely?

There is no risk of any kind as long as there's enough case mouth clearance to the chamber mouth; at least .010" is plenty. All cases head spacing on their shoulders set back .001" or more from firing pin impact. That drives the cas mouth closer to the chamber mouth edge. As long as case mouths don't slam into that angled chamber mouth, the cas mouth won't be crimped into the bullet and raise peak pressures.

 

[Nature Boy]

I trim my .308 to 2.005 as part of brass prep, every time.

Why? Because people more knowledgeable than me told me to. At this stage of my reloading career I figure I better have a damn good reason to deviate from published data or conventional wisdom.

 

[JohnhenrySTL]

I get that many trimmings too. My bullet is slightly smaller and slower. I was hoping to get more. Although My AR seems to wear brass out quicker than my 700.

 

[SavageShooter2k]

Yeah, I am measuring after I resize. I'm going to go ahead and trim them all down. Thanks guys.

 

[fguffey]

Recently I land some really nice once fired Federal brass and I am now looking to put some it to use as some of my PPU brass is starting to fall apart. I have been using PPU for this load exclusively with great success.

I have two lengths, one from the datum/shoulder to the bolt face and the other from the end of the chamber to the bolt face. You said nothing about measuring your cases from the shoulder to the case head before firing and again after firing I will assume you do not know the difference in length between the chamber and case from the shoulder of the chamber to the bolt face and case from the shoulder to the case head.

Meaning: I have one chamber that is .016" longer than a minimum length case from the shoulder of the chamber to the bolt face. That is .012" longer than a go-gage. That is .002" longer than a field reject length gage. I off set the length of the chamber with the length of the case, all I have to keep up with is the case length. When trimming the length of the case I add .014" to the length of the case because of the length of the chamber.

I want the case to cover my chambers.

F. Guffey

 

[Kaldor]

I get that many trimmings too. My bullet is slightly smaller and slower. I was hoping to get more. Although My AR seems to wear brass out quicker than my 700.

That is because your AR stretches the brass everytime it fires when it extracts it. Your 700 does not.

 

[Walkalong]

It's more about fit to the chamber.

 

[RunninLate]

I run all my rifle brass through the trimmer. I am using WFT (Worlds Fastest Trimmer) in a vise and using a foot pedal to turn on and off the drill. Once you get your lenght set in the trimmer, you can check and trim 10+ cases in a minute.

 

[Bart B.]

All the 30 caliber cartridges I've shot in rifles have shorter case lengths after firing. Both bolt action and semiauto. Same for 22 caliber ones.

After full length sizing, they grow almost .001" in length from their original, unfired length.

How much depends on how much head clearance they have as well as how hot the load is.

 

[Sunray]

Federal brass is known for being softer than other brands. It's going to stretch a bit. Check case lengths every time, but trim, chamfer and deburr, as required only.