Case neck trim length necessity?

FORESTBARBER

Private
Full Member
Minuteman
Mar 21, 2010
68
16
69
Fort Worth, TX
I am new to reloading, but have acquired most of what I need and have reloaded some ammunition from all new components.

The trimmed case length is supposed to 2.714. After firing the OAL of case is 2.716.

I have measured the chamber length with a Sinclair button in a new case to be 2.750.

Why if one fl resizes and loads the round otherwise correctly does the neck even need to be trimmed?

Will it ever approach the chamber length?

I could see that a too long case length would have overall more grip/friction on the bullet. Is that the issue.

Illuminate me please, and please excuse my ignorance.

Oh yeah, I couldn't decide which case trimmer to get and don't have one yet.:)

Thanks,

Forest
 

mdesign

Gunny Sergeant
Full Member
Minuteman
Nov 2, 2004
2,124
8
Nebraska
Re: Case neck trim length necessity?

Your brass may never get that long, sort of depends on the cartridge and the brass as some stretch more than others. At least you know the limits of your chamber.

I happen to have a similar situation on a 7RM of mine and the brass has not reached the length of the chamber after many firings (I don't run real hot loads). I just keep my brass trimmed to a consistent length and once and a while I touch up the shoulder/neck area with my neck turner as that is where the brass seems to get the thickest.

You sort of have to watch the carbon ring that will form ahead of the cartridge when you are that short of the end of the chamber. If you shoot a lot of rounds between cleanings as some of us do, this ring can become pretty significant and and may effect accuracy.

I prefer to not have my brass be more than .010 shorter than my chamber for this reason but sometimes it cannot be help as you have noticed.

Good luck learning about reloading.
 

FORESTBARBER

Private
Full Member
Minuteman
Mar 21, 2010
68
16
69
Fort Worth, TX
Re: Case neck trim length necessity?

Swan

I have read all of which you refer to and did so before I bought my first piece of equipment, components, loaded my first round, etc...

It makes little sense to me to need to trim a case that is already .034 short of the end of the chamber. Maybe I have you wrong and you think it doesn't make sense either, but I don't think so.

I take from the para below, quoted from that article, that it is not a necessity in my particular situation until the case approaches the chamber length.

"4. Case Trimming: This part is painful no matter how you do it. It is also the one part that can have disastrous effects if you don’t do it. If the brass grows to the point where it begins to get crushed by the end of the chamber it will essentially add crimp to your round. Add too much crimp and the case will fail catastrophically due to over pressure. There are several choices equipment wise in how to do this operation."

All that said, I'll continue to use new brass until I am absolutely certain of the right course.

Thanks,

Forest
 

FORESTBARBER

Private
Full Member
Minuteman
Mar 21, 2010
68
16
69
Fort Worth, TX
Re: Case neck trim length necessity?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdesign</div><div class="ubbcode-body">Your brass may never get that long, sort of depends on the cartridge and the brass as some stretch more than others. At least you know the limits of your chamber.

I happen to have a similar situation on a 7RM of mine and the brass has not reached the length of the chamber after many firings (I don't run real hot loads). I just keep my brass trimmed to a consistent length and once and a while I touch up the shoulder/neck area with my neck turner as that is where the brass seems to get the thickest.

You sort of have to watch the carbon ring that will form ahead of the cartridge when you are that short of the end of the chamber. If you shoot a lot of rounds between cleanings as some of us do, this ring can become pretty significant and and may effect accuracy.

I prefer to not have my brass be more than .010 shorter than my chamber for this reason but sometimes it cannot be help as you have noticed.

Good luck learning about reloading.</div></div>

Thanks for your insights. I'll continue to tread carefully, ask questions, learn, and for the near term use new brass!

Forest
 

Fuzzball

Gunny Sergeant
Full Member
Minuteman
Jan 19, 2009
2,165
5
Re: Case neck trim length necessity?

"Add too much crimp and the case will fail catastrophically due to over pressure."

As you recognise, you case length is only "critical" in that it doesn't exceed the chamber length. How quickly that may happen depends on a lot of variables we can't honestly predict for you.

It isn't "too much crimp", as such, that causes a pressure problem; no amount of crimping can do that. Problem comes when a bullet is clamped in the case mouth at the end of the chamber and can't be released before pressure skyrockets. It is imperative we not let our cases get long enough to cause that.
 

samnev

First Sargeant
Full Member
Minuteman
  • Mar 16, 2010
    3,934
    100
    Surprise, AZ
    Re: Case neck trim length necessity?

    As stated above if you don't trim and crimp you will eventually crush down the neck into the body of the case. I trim after every firing.
     

    RECKON SO

    Full Member
    Full Member
    Minuteman
    Jul 7, 2009
    101
    0
    Cullman Alabama
    Re: Case neck trim length necessity?

    Ive been trying to get my muzzle velocity spreads down and decided to trim every time, I figure if every case is the same length that cant hurt consistant resistance on the bullet. Its not alot of effort to do, and you can rule out one variable in iterior ballistics. YMMV
     

    FORESTBARBER

    Private
    Full Member
    Minuteman
    Mar 21, 2010
    68
    16
    69
    Fort Worth, TX
    Re: Case neck trim length necessity?

    Thanks all. I will set myself a conservative limit on case length and segregate my brass into groups up to that limit.

    All new and interesting to me.

    I have Giraud trimmer on order and look forward to using that in a few weeks.

    Regards all,

    Forest
     

    nhm16

    Sergeant
    Full Member
    Minuteman
    Jan 31, 2009
    283
    1
    Houston, TX
    Re: Case neck trim length necessity?

    Get these chamber length gauges from Sinclair, follow the instructions to measure. It may be the case that your chamber length is long enough that you require no trimming. I don't trim unless and until the case length grows to within ~0.015" of the chamber length. Lots of discussion on this site and 6mmbr about how much to trim.
     

    FORESTBARBER

    Private
    Full Member
    Minuteman
    Mar 21, 2010
    68
    16
    69
    Fort Worth, TX
    Re: Case neck trim length necessity?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nhm16</div><div class="ubbcode-body">Get these chamber length gauges from Sinclair, follow the instructions to measure. It may be the case that your chamber length is long enough that you require no trimming. I don't trim unless and until the case length grows to within ~0.015" of the chamber length. Lots of discussion on this site and 6mmbr about how much to trim.

    </div></div>

    Thanks. I have the gauges (gages?) you cite and the chamber measures 2.750". It seemed too obvious that case length of 2.716" did not need to need to be trimmed, but as a novice I wanted to be sure.

    Forest
     

    FORESTBARBER

    Private
    Full Member
    Minuteman
    Mar 21, 2010
    68
    16
    69
    Fort Worth, TX
    Re: Case neck trim length necessity?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RJ Hunter</div><div class="ubbcode-body">There is a much easier way. Get a Giraud case trimmer and run all of your brass into it after you size. Cases will stay the same length, necks will have a better chance of having the same tension, and you will save time over measuring all of that crap. Oh yea, its safer! </div></div>

    Makes sense. I have the Giraud on order and will use it on .308 as well.

    Thanks,

    Forest
     

    FORESTBARBER

    Private
    Full Member
    Minuteman
    Mar 21, 2010
    68
    16
    69
    Fort Worth, TX
    Re: Case neck trim length necessity?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Santo</div><div class="ubbcode-body">As stated above if you don't trim and crimp you will eventually crush down the neck into the body of the case. I trim after every firing.</div></div>

    The case length is .030+" short of my rifle's chamber length of 2.750. I'll monitor length carefully and probably decide to trim them all when I get the Giraud trimmer.

    Thanks,

    Forest