The Firing Line Forums

Go Back   The Firing Line Forums > The Skunkworks > Handloading, Reloading, and Bullet Casting

Reply
 
Thread Tools
Old May 2, 2012, 07:57 PM   #1
Arizona Smithshooter
Senior Member
 
Join Date: August 20, 2011
Location: Western Arizona
Posts: 167
Why Trim?

The never exceed case length of Remington .223 cases is 1.760". So what happens if the case length is 1.764, 1.767, etc? I have been trimming my cases using a Lee trimmer and they come out about 1.754", but it's a slow process. I am using a Hornady LnL press, using Hornady dies, firing them in my M&P 15. Just wondering if it really matters as long as the COAL is within Spec.
Arizona Smithshooter is offline  
Old May 2, 2012, 08:00 PM   #2
hk33ka1
Senior Member
 
Join Date: April 20, 2010
Posts: 275
Depending on how long the chamber is in your gun it may squish the longer case into the bullet causing trouble chambering, extracting and higher pressures when firing. Your chamber would in effect act like the crimping portion of a seater die. Yes you do need to trim them.

Do you have a Lee Zip Trim or spin the cases in a drill with the Lee system? These options make it a lot quicker.

If you have a ton of cases to do you might look at the Giraud Trimmer.
hk33ka1 is offline  
Old May 2, 2012, 08:25 PM   #3
jepp2
Senior Member
 
Join Date: December 24, 2008
Location: Loveland, CO
Posts: 1,370
If you get a Sinclair Chamber Length Gage you can measure the actual length for your rifle. The 1.760" value was created by SAAMI to be safe for all firearms.
jepp2 is offline  
Old May 2, 2012, 09:11 PM   #4
Arizona Smithshooter
Senior Member
 
Join Date: August 20, 2011
Location: Western Arizona
Posts: 167
I use a Lee Case Trimmer Cutter and Lock Stud mounted in my power drill that works great, just time consuming. Most of the time the cases I have trimmed are within spec after a couple of reloads. I kind of knew the answer before I asked the question...just needed some conformation to show my neighbor because he never trims and tells me I am wasting my time.
Arizona Smithshooter is offline  
Old May 4, 2012, 05:29 PM   #5
Ozzieman
Senior Member
 
Join Date: December 14, 2004
Location: Northern Indiana
Posts: 5,027
higher pressures when firing

hk33ka1, I couldn't have said it better.
Ozzieman is offline  
Old May 4, 2012, 05:36 PM   #6
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 10,465
I'll add only that the SAAMI spec. is 1.740" to 1.760". If you sand a little steel of the tip of the Lee gauge, you can cut them down to the lower end of that range and may be able to reload three or four times before you have to trim again. The only reason to trim every time is if you are roll crimping into a bullet cannelure, in which case you need the most consistent length possible to get consistent crimp tension. Indeed, some M14 match shooters used to trim 0.015" to 0.020" below SAAMI minimum, just so they'd never have to trim again before retiring the cases (usually after about 5 full power loadings total, including the first, for military brass in that gun to avoid chances of head separations and case blowouts)
__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member
Unclenick is offline  
Old May 4, 2012, 06:26 PM   #7
amamnn
Senior Member
 
Join Date: May 13, 2006
Location: WA, the left armpit of the USA
Posts: 1,323
For shooters who can take advantage of the tighter tolerances of custom built rifle barrels--the ideal is to have all the cases be of the same shoulder datum length and also of the same trim length which presupposes a set neck length which results in the same bearing surface and bullet release. For BR shooters, the equipment and time and money invested in determining these data along with others, are worth the blood and treasure, so to speak.
The Lee trimmers will do an adequate job for most of the rest of us. They trim to "Lee length" which is somewhere between the min and max recommended lengths. If you have set up your sizing die to match your chamber fairly well, you will not need to worry about it. A case that is not worked too hard will not need to be trimmed all that often--this is especially true of cases fired in bolt action chambers, but it is also true of direct gas impingement action rifles, though you may have to trim a bit more often.
__________________
"If the enemy is in range, so are you." - Infantry Journal
amamnn is offline  
Old May 4, 2012, 08:11 PM   #8
Salmoneye
Senior Member
 
Join Date: December 31, 2011
Location: Vermont
Posts: 1,409
Trimming with a Lee is 'slow?



Never seen one in any caliber that took more than a simple twist per case...

The Lee trimmer is the fastest I have ever seen...Try setting up a Redding case trimmer, and make sure you have your calipers handy...
Salmoneye is offline  
Old May 4, 2012, 11:45 PM   #9
joneb
Senior Member
 
Join Date: December 10, 2005
Location: Central , OR
Posts: 1,732
Quote:
Why Trim?
Not trimming your cases may cause blindness
joneb is offline  
Old May 5, 2012, 12:08 AM   #10
zxcvbob
Senior Member
 
Join Date: December 20, 2007
Location: S.E. Minnesota
Posts: 4,215
Yes the case length matters, but I've never found a "FC" headstamp once-fired case that needed trimming -- they seem to start out short. Also the steel Wolf and Tula cases are reloadable and don't stretch (at least I think they don't, I haven't reloaded them very many times yet)

I resize and trim "LC" (and other) cases while I sit and watch TV. So when I'm ready to reload the cases are ready to go. I use a Lee trimmer and a cordless drill.

If you're loading .223 on a progressive press, you might wanna get a RCBS X-sizer die. It has a stop to prevent the cases from stretching when you resize them. (I have one in .30-06 but I haven't used it much.)
__________________
"The only way to stop a bad guy with a gun is with a good guy with a gun"
zxcvbob is offline  
Old May 5, 2012, 08:17 AM   #11
Arizona Smithshooter
Senior Member
 
Join Date: August 20, 2011
Location: Western Arizona
Posts: 167
What I meant was when I said trimming is a slow process using the Lee trimmer was that it is time consuming to run 100-300 cases through the trimmer...especially when compared to my friend who thinks that part of case prep is time wasted. I have found that the cases I have trimmed have all remained in spec after 2 or 3 more times through the sizer die.
Arizona Smithshooter is offline  
Old May 6, 2012, 02:08 PM   #12
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 10,465
Rifle cases, except very short ones, usually have a length tolerance of -0.020" from maximum. Most case trimmers and manufacturers aim for the middle of that range, which is -0.010" from maximum, to have ±0.010" wiggle room.

When the case is fired it expands to fill the chamber. When you size it back down, the expanded diameter is squeezed by the die, flowing a little of the brass rearward, but mainly just drawing the whole case longer. The shoulder portion of the full length sizing die then pushes the lengthened shoulder back in place. The excess brass from that part of the sizing has to go somewhere, so it flows forward into the neck area.



So, how much will your case grow? Well, how much wider and longer than the sizing die profile was it when you pushed it in? Is your die on the large side of diameter or small side or even a small base die diameter? Those are the main factors that determine growth during resizing. If you never squeeze the case back toward original diameter (neck sizing only) you may never see significant growth. If you full length resize, but your chamber is tight, growth may remain quite small. If your fire at modest pressure levels the brass won't stretch as sharply into the chamber profile and will grow less than a maximum pressure load will, so it gets squeezed back less during sizing and grows less. If you fire at peak pressures under about 30,000 psi with most powders, the case backs up in the chamber rather than sticking to the chamber walls, so there is no stretching at the pressure ring, and that means they may need very little shoulder setback and don't grow appreciably.

In the extreme, you often see low pressure straight wall pistol cases actually shrink with each resizing because they backed up into the chamber, were blown out shorter and fatter rather than stretching, and during resizing the amount of brass flowed rearward exceeded the stretch back toward original length. I once tracked a bulk purchase of .45 ACP cases through 50 reloading cycles with light target loads, and at the end, the ones that hadn't split at the mouths and been tossed or hadn't been lost to the range gods were all about 0.025" shorter than what they started out with. A loss of about half a thousandth per load cycle.

On the other hand, I used to get an average of about 0.005" growth after resizing .308 rounds run through my M1A. But I would get a few that grew 0.007" and a very occasional 0.010", and a few that seemed not to grow only a thousandth or two if at all. These were same-brand cases first fired in my gun and having the same load history thereafter. Back then I didn't have the tools I do now, but if I had, I expect I'd have found the long ones were light or had uneven wall thickness so the thin area could fill the chamber more tightly. The ones that didn't grow may well have had the brass flow into the body and shoulder junction more than the neck, perhaps due to inadequate lube on the shoulder during resizing. They may also have been heaver and more uniform than average so they had more spring-back in the chamber. There are a multitude of possible explanations for why one case stretches more or less than the next.

The bottom line is if you are full length resizing, you want to check every case with a gauge or a caliper after resizing so you find the outliers. Don't measure just a couple and count on them all being the same. If you want to crimp you may have to trim every time to keep the crimp pressure uniform.

If you need speed for trimming a volume of cases, there are a couple of motorized routes. The Gracey trimmer has been around the longest and works just fine. The Giraud is the Cadillac in terms of construction, with ball bearings and the like and a bigger motor. These two trimmers do two things most others do not. One is they set trim length off the case shoulder, which eliminates the step of having to put the cases into some kind of separate holder. The other is they feature custom shaped cutters that chamfer and deburr the cases simultaneously as they trim, eliminating the need to perform those two additional operations.

There are a couple of less expensive trimmers that register off the case shoulder head, the Possum Hollow Kwick Case Trimmer and Little Crow's WFT trimmer. The first may be adapted to a drill while the second requires a drill. Neither does simultaneous deburring and trimming.
Attached Images
File Type: gif shoulder setback.gif (45.9 KB, 63 views)
__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member
Unclenick is offline  
Old May 6, 2012, 06:17 PM   #13
Jimro
Senior Member
 
Join Date: October 18, 2006
Posts: 5,761
I've been using a Possum Hollow to go through the 2000 cases I bought from gibrass.com. Even with the tool chucked into a drill it feels like slow going, but it is about 2 to 3 times as fast as using a Lee trim system that requires chucking every piece of brass into the holder... Once trimmed I toss them in a box and deburr by hand as that doesn't take long at all.

Best 35 bucks I've spent on reloading gear in a while.

Jimro
__________________
"Gorsh" said Goofy as secondary explosions racked the beaten zone, "Did I do that?"

http://randomthoughtsandguns.blogspot.com/
Jimro is offline  
Old May 6, 2012, 06:29 PM   #14
Arizona Smithshooter
Senior Member
 
Join Date: August 20, 2011
Location: Western Arizona
Posts: 167
Thanks Unclenick ...like they say a picture is worth a thousand words. I appreciate your taking the time to go into such a detailed explanation. Makes me feel better about the time I spend prepping my cases.
Arizona Smithshooter 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 -5. The time now is 04:31 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2014 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.09464 seconds with 10 queries