Do you have to trim necked sized rifle brass?

[John C]

I've finally ordered some cases and bullets, and I'm going to start reloading rifle rounds for the first time. I'm loading 8mm Mauser. I know there's a lot of case prep necessary in loading for bottle-necked rifle brass. I've reloaded straight-walled pistol brass for 8 years, so I'm familiar with reloading.

I have two questions:

1) Once I full length size, trim, and reload the brass (I bought once-fired cases), and shoot it in my rifle, do I need to trim the brass if I only intend to neck-size the brass? I'm not clear if trimming is only necessary after full-length sizing, or not.

2) Do straight-walled rifle cases, like .45-70, need to be trimmed after resizing? Or do they load like pistol cases?

Thanks,

-John

 

[243winxb]

Anytime the brass exceeds the maximum case length listed , it needs to be trimmed.

 

[rsrocket1]

Always check your case lengths before each reload. It's easy and fast. Simply set your calipers to the proper length, set the lock screw and its now a go/no-go template.

It's also a good idea to run your prepped empty cases through your gun to make sure your the shoulders are bumped back enough and the case chambers easily. There is nothing more frustrating than to go out to the range with a bunch of shells that won't chamber or chamber very tightly.

 

[John C]

Thanks, guys, for the info. I should have clarified that I intend on checking the case length. I'm just wondering if I will likely need to trim every time. My understanding (and please correct me if I'm wrong), is that cases lengthen due to being stretched when fired and then resized. So I'm wondering if I fire-form the cases and only neck size them, won't my cases expand and contract less, therefore lengthen less? Based on your experiences, will I still need to trim every time? Obviously, many variables are in play here, so I'd just like a generalization.

Thanks,

-John

 

[jmorris]

As you know you have to check but they don't grow much if you only neck size them.

 

[243winxb]

Based on your experiences, will I still need to trim every time?

No, because many bottle necks when they exceed the maximum are trimmed back .010" This is what keeps you from having to trim each time. Neck sizing only will not be needing trimming as often. If your using a Lee trimmer, you may have to trim almost everytime.

 

[NeuseRvrRat]

if you measure your chamber with a sinclair chamber length gauge or a flat base bullet seated upside down, you will find that on most hunting rifles there is plenty of extra chamber beyond the book trim length (.020-.030" in my experience). if you go conservative and use .010" short of this measurement as your max case length, you will rarely have to trim cases. measure the chamber several times to make sure you're getting a good measurement. if you let the case get too long and jam it up past the end of the chamber, you could get a pressure spike.

 

[243winxb]

a flat base bullet seated upside down, you will find that on most hunting rifles there is plenty of extra chamber beyond the book trim length (.020-.030" in my experience).

I think you are measuring the throat, not the chamber. Put the thickness of the brass neck on the end of the backwards bullet, see what you get.

 

[NeuseRvrRat]

i think you're correct. i just use the sinclair gauge, which steps out to the OD of the case neck.

 

[243winxb]

I thought i was correct, just never 100% sure. Thank you. SAAMI shows the 243 Win. chamber has what i call a "safety zone". When the brass is at the maximum length, there is still .010" chamber length left. So If you forget to trim, there is that safety margin. I did measure my chamber, so i know i have the safety zone. As little as .003" in some, so always trim brass when it exceed the listed maximum.

 

[Sin City Shootist]

I don't trim most of the time now. I bought a case length gauge for my .308 and found its max length was .2.055. I also don't crimp any longer, so a bit more surface area to hold the bullet is a plus for me.

 

[Clark]

At 66kpsi 223 brass with the shoulder pushed back .005" will grow to need trimming in one or two firings.

At 66kpsi 223 brass that is neck sized will grow to need trimming in 20 firings.

 

[gamestalker]

Yes. Every cartridge has a specified max and trim to length, and it is to manage pressures.