Quantcast
case trim length - THR
THR  

Go Back   THR > Ammunition, Gear, and Firearm Help > Handloading and Reloading

Welcome to THR
You are currently viewing our site as a guest which gives you limited access to view most discussions, articles and access our other FREE features. By joining our free community you will have, access to post topics, communicate privately with other members (PM), respond to polls, and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!


If you have any problems with the registration process or your account login, please visit the help section.

Reply
 
Thread Tools
Old November 28, 2014, 04:45 AM   #1
Aceroc
Member
 
 
Join Date: November 28, 2014
Posts: 2
case trim length

I know this has been discussed hundreds of times I just want to get everyone's opinion . I been reloading awhile and been just reloading to Sammi specs. Recently I been reading a lot about more things to do to get better accuracy. I just ordered a oal gauge and a comparator to try and get closer to the lands and measure the ogive. My question is how consistent does the trim length need to be? Most of my brass is 1.752 to 1.756. I have some brass that is 1.745 to 1.749 but that is separate. Will the difference in thousands affect the accuracy or bullet seating? Thanks
Aceroc is offline  
Old November 28, 2014, 07:17 AM   #2
noylj
Member
 
 
Join Date: July 27, 2007
Posts: 935
Do you have a multi-thousand dollar custom rifle? Do you shoot at over 600 yards? A no to either question means: it just doesn't matter.
At some point you will have to trim the cases, as bottleneck cases to grow (unless you have the shoulder and case head in tight contact with the chamber and breech), so you can trim them all fairly exactly with any good trimmer.
Case length does not effect bullet seating, as that is determined by the distance from the seating stem to the shell plate. You may find a few thousandths difference, based on variations in pressure you use on the press handle and any variations between the seating stem and the bullet (the better the match between the two, the better the consistency and less run-out).
__________________
I will remind you what the road to hell is paved with…good intentions. When you decide you know better than someone else how their life should be lived, you are on the road to becoming the next Dark Lord.
noylj is offline  
Old November 28, 2014, 09:17 AM   #3
345 DeSoto
Member
 
 
Join Date: January 5, 2008
Location: Skaneateles,NY Summer/Port St.Lucie,FL Winter
Posts: 411
What caliber are you loading for?
__________________
"Any man who thinks he can be happy and prosperous by letting the Government take care of him; better take a closer look at the American Indian!"
-Henry Ford-
345 DeSoto is offline  
Old November 28, 2014, 09:33 AM   #4
stubbicatt
Member
 
 
Join Date: August 23, 2007
Location: Colorado
Posts: 3,003
My $.02

Trim length can affect the buildup of a carbon ring at the end of the chamber just before the leade portion of the barrel. This carbon ring can constrict passage of the bullet into the rifling both affecting accuracy and creating a pressure problem. First order of business is removing the carbon buildup (if it exists), and then trimming the case necks to fit your chamber.

In order to determine trim length for your chamber, Sinclair sells little plugs that can help you. To use the little plugs, cut a case neck on a sacrificial case and chamber the case with the plug seated in it. You now know your chamber neck length dimension.

The trim to length, by my way of seeing it, is the chamber length determined by the Sinclair plug, minus .003" to .005"

This will prevent future formation of that carbon ring which is the goal of this exercise.

Hope this helps a little bit.
__________________
Hate is a poison which one consumes expecting another to die.

Last edited by stubbicatt; November 28, 2014 at 09:42 AM.
stubbicatt is offline  
Old November 28, 2014, 11:17 AM   #5
243winxb
Member
 
 
Join Date: July 8, 2004
Location: USA
Posts: 6,359
presicion target rifles

Quote:
My question is how consistent does the trim length need to be?
I keep my 243 win brass at SAAMI maximum for the target rifle. This may require trimming about every 2 or 3 loadings when it goes a few thousands over. I have measured the chamber length and it showed i have a "safety zone" that will allow a slightly longer maximum trim length. Neck tension/bullet pull would be different between short and long trim lengths. Trying to reach the rifling by seating long is not always a good thing with a factory rifle. Start with the bullets base, full diameter, at the neck/shoulder junction. Adjust OAL to fit chamber and magazine.
243winxb is offline  
Old November 29, 2014, 11:42 AM   #6
spitballer
Member
 
 
Join Date: December 20, 2013
Location: Central FL
Posts: 452
Presumably this is for a .223. I simply trim my cases to 1.75" when they get to 1.76". Just how much effect trim length has on accuracy is open to debate; cases that are trimmed shorter could conceivably allow more blow-by if the bullet is some distance off the lands. Slop in this area can be reduced by ordering an undersized neck with your next barrel change, but you'll have to keep a close eye on brass thickness if you go this route.
__________________
"Theories, Spock?"

"None."
spitballer is offline  
Old November 29, 2014, 12:46 PM   #7
Aceroc
Member
 
 
Join Date: November 28, 2014
Posts: 2
Yeah sorry it's for .223. Guess my question would be would the difference in thousands effect accuracy? Should I trim them all as close to the same length as possible or would I be wasting my time trimming a few thousands off?
Aceroc is offline  
Old November 29, 2014, 01:49 PM   #8
moxie
Member
 
 
Join Date: December 30, 2002
Location: Erath Co., TX
Posts: 2,301
They don't all need to be the same, and if you reload and shoot a lot they won't be.

Just measure each case after sizing. If they are longer than 1.76, as noted above, trim to 1.75. If shorter just leave them alone. They are good too.
__________________
"If you have to shoot...shoot...don't talk." Tuco

U.S. Air Force Munitions, 1969-1992
Vietnam, 1972-1973
moxie is offline  
Old November 29, 2014, 02:37 PM   #9
Sunray
Member
 
 
Join Date: May 17, 2003
Location: London, Ont.
Posts: 8,287
The key to consistently good ammo is consistency in all the bits. As daft as that sounds. Trimming the cases so they're all the same is the easiest thing to do. However, as mentioned, if it's for a hunting rifle, it's not going to make a whole lot of difference.
Sunray is offline  
Old November 29, 2014, 04:05 PM   #10
brickeyee
Member
 
 
Join Date: February 25, 2005
Posts: 3,125
Unless the gun us already set up with better than normal accuracy it is not going to matter.
brickeyee is offline  
Old November 30, 2014, 05:23 AM   #11
jeepmor
Member
 
 
Join Date: November 6, 2005
Location: Stumptown
Posts: 2,794
I follow Moxie's methods. Trim when too long after resized and decapped. Leave alone when in that typical 0.010 window. Saves a lot of trimming by the way as I can measure with calipers and make a trim and no trim pile much faster than I can trim everything. Use this on all my rifles, all are hunting rifles except for one, so I don't bother going all snipercentral on my brass prep as I have not seen it make much difference when I tried.
__________________
We hang the petty thieves and appoint the great ones to public office.
jeepmor is offline  
Old November 30, 2014, 06:42 AM   #12
rskent
Member
 
 
Join Date: May 28, 2006
Location: The land of blue sky and sunshine
Posts: 741
I think it's faster to just trim them all. Assuming your trimmer is already set up. For me running them through the trimmer takes less time than measuring them.
I check the first few trimmed cases to check the setup. After that I just trim them. If the cutter cuts them they needed trimming. If the cutter doesn't cut them
they didn't need trimming. Either way, there done.
__________________
How can you not love a G19?
Steve
rskent is offline  
Old December 1, 2014, 09:39 AM   #13
FROGO207
Member
 
 
Join Date: December 7, 2008
Location: Mount Desert Island Maine
Posts: 5,059
The only advantage to trimming them all to a specific length is realized IF you are going to crimp the bullets in. Then there is more consistency in the bullet pull on release. Nothing I own will require removal of that carbon ring to improve accuracy either. I am a bit lazy at times and if I pick up a piece of brass rather than measure it then trim it is easier to just trim them all with the Lee length trimmer chucked into a cheap drill press. YMMV
__________________
The west was not won with a registered gun!!
Don't let our government make us into outlaws
NRA Life Member.
FROGO207 is offline  
Old December 1, 2014, 09:41 AM   #14
FROGO207
Member
 
 
Join Date: December 7, 2008
Location: Mount Desert Island Maine
Posts: 5,059
Double post sorry.
__________________
The west was not won with a registered gun!!
Don't let our government make us into outlaws
NRA Life Member.
FROGO207 is offline  
Old December 1, 2014, 10:47 AM   #15
Yetiman
Member
 
 
Join Date: April 21, 2014
Location: SE Wisconsin
Posts: 10
Stubbicat said:
My $.02

Trim length can affect the buildup of a carbon ring at the end of the chamber just before the leade portion of the barrel. This carbon ring can constrict passage of the bullet into the rifling both affecting accuracy and creating a pressure problem. First order of business is removing the carbon buildup (if it exists), and then trimming the case necks to fit your chamber.

In order to determine trim length for your chamber, Sinclair sells little plugs that can help you. To use the little plugs, cut a case neck on a sacrificial case and chamber the case with the plug seated in it. You now know your chamber neck length dimension.

The trim to length, by my way of seeing it, is the chamber length determined by the Sinclair plug, minus .003" to .005"

This will prevent future formation of that carbon ring which is the goal of this exercise.

Hope this helps a little bit.


This is exactly what I use and do. I don't think you will see a noticeable difference in accuracy for your use, but it is the best way to prevent carbon build up and to prevent chamber deterioration that can come from always using short brass.
Yetiman is offline  
Old December 1, 2014, 10:47 AM   #16
spitballer
Member
 
 
Join Date: December 20, 2013
Location: Central FL
Posts: 452
Quote:
Originally Posted by Aceroc View Post
Should I trim them all as close to the same length as possible or would I be wasting my time trimming a few thousands off?
There doesn't seem to be much argument about consistency being the key to accuracy, and I tend to sweat details like this, too. My main concern is cases that are smooshed out so long that they start curling up against the bottom of the bore and cause pressure spikes. I first noticed this several years ago: I couldn't figure out why my nice clean chamfers were curled up after firing until I measured OAL of the cases and realized that they needed trimming. I've always been a bolt fan and I don't know a lot about autoloaders, but I suspect that trim length is very important for autoloaders because it determines, in part, where the crimp is going to be. I may be speculating here, but I suspect that understanding and mastering crimps is going to greatly contribute to the accuracy of an autoloader if this is what you're using. Others may know more about this.
__________________
"Theories, Spock?"

"None."
spitballer is offline  
Reply


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:36 AM.


Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
vBulletin Optimisation by vB Optimise.
This site, its contents, Shooting Reviews, and its contents are Copyright (c) 2010-2013 Firearms Forum, Inc.
IMPORTANT DISCLAIMER
Although The High Road has attempted to provide accurate information on the forum, The High Road assumes no responsibility for the accuracy of the information. All information is provided "as is" with all faults without warranty of any kind, either express or implied. Neither The High Road nor any of its directors, members, managers, employees, agents, vendors, or suppliers will be liable for any direct, indirect, general, bodily injury, compensatory, special, punitive, consequential, or incidental damages including, without limitation, lost profits or revenues, costs of replacement goods, loss or damage to data arising out of the use or inability to use this forum or any services associated with this forum, or damages from the use of or reliance on the information present on this forum, even if you have been advised of the possibility of such damages.