Trimming new brass

GILLY

GILLY

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I just went through a bag of 50, Remington, 7mm RM cases, every single one of them required a little bit of trimming. I was suprized at this as I thought that factory stuff was automatically sized prior to packaging.Anyone else size new out-of-the-bag brass.

I'm really glad I did this, it takes away yet another variable to my load tweaking.
 
If they came in a bag they're likely once fired. Checking the length isn't a bad idea though. Manufacturing tolerances will leave virgin brass slightly different in length. New brass needs to be run through a sizing die then have the case mouth chamfered on the inside.
 
sunray said:
If they came in a bag they're likely once fired. Checking the length isn't a bad idea though. Manufacturing tolerances will leave virgin brass slightly different in length. New brass needs to be run through a sizing die then have the case mouth chamfered on the inside.
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Most brand new brass comes in a bag now days, doesn't it?:confused:

Unless it is way out of spec, don't trim until after the first firing. The brass is not all exactly the same before the first firing, and will not all fire-form exactly the same. Once it has been fireformed to YOUR chamber, and resized by YOUR size-die, you then have a better chance of maintaining uniformity. IMHO.
 
I trim mine as well. the brass is manufactured to SAAMMI length, but trim length is usually .010 shorter so you don't have to trim it after every loading.
 
I size and trim new brass .010" shorter than max length as well as primer pocket uniforming and flash hole deburring, I like to get it over with then I know all the steps I use have been done to all my brass. The last batch of two hundred 338 RUM brass I did were almost all bang on the same length, some just took a skim off the case neck.
 
SuperCub said:
I always trim and resize all new brass.
They come in all lengths and sizes. :confused:
sc
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+1 !!! Especially winchester brass for some reason???

It's always a bit too long. I give it a quick spin and chamfer to uniform it after a full-length size. After that, I foreform on a plinking range trip and revert to neck sizing that brass for serious loadings.

Also, I've noticed ALOT of Winchester .45-70 brass is poorly edge cut, often with lips of extra brass not properly faced off the case mouths - seems quality is on the downturn of late :( but it could be worse - it could be FEDERAL brass! Yikes!

Remingto nseems the best brass lately in the stuff I've ben buying.
 
SuperCub said:
I always trim and resize all new brass.

They come in all lengths and sizes. :confused:





sc
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This is why I say not to trim until they are fireformed.

Because the brass is all sizes out of the bag, I think if you trim to all the same length and then fireform, they each form differently as they fill your chamber for the first time. The result could be a bunch of brass all different lengths again after 1 firing. After fireforming, and then trimming, you have a better chance of them all staying the same length, stretching equally after each firing/sizing.

Does that make sense, or am I being too picky? That's why I do it, it doesn't make it right or wrong.
 
joe-nwt.....you make perfect sense. I think I'll do this next time I buy a bag of brass. I have a fresh bag of 22-250 that I will try this method with. Then it will be fire formed to my encore and after trimming, they should all be the same, with very little variables from case to case.
 
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