Trimming brass

I'm still very new to reloading and wondering how often I should trim brass? I know this is going to require measuring each piece of brass after firing and trimming accordingly. I just don't know what the parameter should be. 90% of my reloading right now is for 7 Rem Mag. Do most guys trim after every firing?

Also, should I measure the thickness of the brass in the neck of each case after firing?

I originally joined LRH because I wanted to really learn reloading and it has been very helpful. Everyone is always very patient with elemental questions.

You'll likely get different answers on this topic but I trim a group of brass if one piece is longer than the max length spec. I reduce the length by 0.005"

For the safety aspect, if you are shooting a factory rifle, chamber a new piece of brass and then run a borescope from the muzzle end I bet you will see up to .050" from case mouth to end of chamber wall. You will wear out the primer pockets/web before getting to the case mouth to touch the end of the chamber.

For the consistency aspect, you can measure the new brass OAL, and set the trimmer up to the shortest length. You can then run all brass from the bag or box and they grow relatively the same. If you need the brass to hit a cannelure you select the brass length that lets that happen.

Understand if you are using a trimmer that indexes off the shoulder to cut the necks, you will need your shoulder set backs from sizing to be pretty consistent in length.

I personally like the necks as long as possible for straight alignment of bullet seating. 7RM doesn't have much neck length to begin so I wouldn't want to be cutting down much at all.

I have found that new brass will stretch the most on the first firing. After the first firing, I will trim all brass after resizing so that it will all be uniform in length. Then after that, I try to keep the brass in lots, keeping records of the times loaded, and then trim all the ones in that lot to the shortest one as long as it has not exceeded the max case length.

IMHO, let's take for instance the 308 case. Maximum length is 2.015 and recommended trim is 2.005. After sizing my brass, if any is over 2.010 I will trim back to 2.005. Maybe I'm a perfectionist but I try to have just about everything the same on the brass I'm using; same length and same neck tension by using a mandrel.

Once I get to max listed length, I trim to minimum "trim to" length. I use the Forster 3-way cutting heads. Takes about 10 seconds per case to insert, trim, chamfer, deburr, and drop in a single step.

For 7RM, that is about every third firing in my rifle and the way I FL size. I bump shoulders .0025" just like any other case.

I trim every firing for consistency sake. The Giraud trimmer makes it quick and painless.

Bominiscious said:

I'm still very new to reloading and wondering how often I should trim brass? I know this is going to require measuring each piece of brass after firing and trimming accordingly. I just don't know what the parameter should be. 90% of my reloading right now is for 7 Rem Mag. Do most guys trim after every firing?

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No! 2.500" +/- .005" or whatever your reloading manual recommends.

Bominiscious said:

Also, should I measure the thickness of the brass in the neck of each case after firing?

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I do not unless you suspect something is wrong.

Bominiscious said:

I'm still very new to reloading and wondering how often I should trim brass? I know this is going to require measuring each piece of brass after firing and trimming accordingly. I just don't know what the parameter should be. 90% of my reloading right now is for 7 Rem Mag. Do most guys trim after every firing?

Also, should I measure the thickness of the brass in the neck of each case after firing?

I originally joined LRH because I wanted to really learn reloading and it has been very helpful. Everyone is always very patient with elemental questions.

Click to expand...

OP,
Just to clarify "Trimming brass" refers to reducing the length of the brass by trimming at the end of the neck. This prevents the neck brass from swaging on the bullet when chambered if the neck brass is really long. This could cause an over pressure situation.

"Turning brass" refers to turning down the wall thickness of the brass in the neck to get a more uniform neck tension for consistent bullet release and corresponding better precision on target.

The title of your question was trimming and then you asked about measuring neck wall thickness so just wanted to make sure we're all on the same page/ process.

PddPdd said:

OP,
Just to clarify "Trimming brass" refers to reducing the length of the brass by trimming at the end of the neck. This prevents the neck brass from swaging on the bullet when chambered if the neck brass is really long. This could cause an over pressure situation.

"Turning brass" refers to turning down the wall thickness of the brass in the neck to get a more uniform neck tension for consistent bullet release and corresponding better precision on target.

The title of your question was trimming and then you asked about measuring neck wall thickness so just wanted to make sure we're all on the same page/ process.

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Yes and thanks for the question. Making sure I'm phrasing things right and asking the right question is also helpful in me learning the details of this. I was talking about reducing the length by trimming back the end of the neck. Several pieces of my brass were measuring 2.5+.

Used to trim a lot until I got a borescope. The borescope proves you don't have to trim as often as most people think.

Straight Shooter said:

Used to trim a lot until I got a borescope. The borescope proves you don't have to trim as often as most people think.

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It's like this has been mentioned before...

Imagine all the hand loaders who have their Jump/DTL to the decimal inches, but then subscribe to an arbitrary trim length without ever really verifying that length. LOL

I go a different approach. I allow my brass to grow within .010" of chamber end while trimming enough off to keep them square, a couple of thou' to square up, then I keep them at that length.
When I form brass for another cartridge, I deliberately choose a case that will form long because when you Improve a case and blow it out, it shortens.
You do not need to trim back to the 'trim-to' length until the brass hits maximum length or whatever max length you have determined.

Cheers.

I'm learning a lot