40SW case variation - Handguns and Ammunition Forums
Forum Home    ::    Active Topics    ::    Hi-Powers and Handguns    ::    Stephen Camp's Blog    ::    Contact Us
Go Back   Handguns and Ammunition Forums > Ammunition & Gunsmithing > Reloading
Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 02-25-2017, 01:25 PM   #1
Member
 
Join Date: Feb 2017
Posts: 2
40SW case variation

I did a random weight check on my 40SW brass (assorted headstamps). It was cleaned and unprimed--just the brass. I checked the case length and they were all the same, but as much as 10.5 grains weight difference!!! Is that too much? I don't usually sort handgun brass, but should I?
Hubcap500 is offline   Reply With Quote
Old 02-25-2017, 02:16 PM   #2
Member
 
gt40doc's Avatar
 
Join Date: Feb 2011
Posts: 613
I would not be concerned about the weight difference in various brands of brass cases. Many of us shoot range pickup/multiple brand brass with no problems. IF you are shooting bullseye 50 yard competition, then I would stick with one brand of brass, plus many other considerations. If you are a range shooter like many of us......load it up and enjoy!!!
gt40doc is offline   Reply With Quote
Old 02-25-2017, 09:20 PM   #3
Member
 
Join Date: Feb 2017
Posts: 2
I'm not as concerned about the lack of weight uniformity. I doubt there are many, if any, people who could tell the difference in accuracy with a hand-held firearm at normal pistol distances with the kinds of deviations I'm talking about here. I'm not talking about bench-rest accuracy.

My concern is not the presence of the weight/capacity deviation, but the amount of deviation-- well over 10%. I don't know how much a % of change in case capacity affects pressures, only that it most certainly does. All reputable manuals advise reloaders of semi- or full-auto firearms to make sure the ammunition does not allow for bullet setback for this very reason.

My concern is about the safety of the ammo, because the weight is a factor in determining case capacity, and therefore pressure, and therefore safety.

If you change your powder charge by that amount, you can very quickly go from safe to unsafe (or vice versa) pressures. It's also my understanding that, because of the nature of smokeless propellants, the pressure curve can rise exponentially rather than linearly at unsuitable pressure levels (high or low).
Hubcap500 is offline   Reply With Quote
 
Old 02-26-2017, 01:53 PM   #4
Regulator
 
abninftr's Avatar
 
Join Date: Jun 2005
Posts: 3,204
Your concern is valid particularly if you are loading at or near max. The difference in case wall thickness, since it obviously means the inside diameter would be smaller and, as a result case volume would be reduced; or that the case base is thicker with the same result, would translate to higher chamber pressures.

That said, perhaps the easiest solution might be to reduce your powder load from max to max minus 10%.

I personally sort my cases by manufacturer before reloading them. I also check my fired cases for flattened primers before cleaning them. Flattened primers are a reasonable indicator of excessive chamber pressure.

ADDED THOUGHT:
There is also a possibility of having unburnt powder left in the case if the case volume is reduced and there isn't sufficient space even if pressures are not excessive.

Last edited by abninftr; 02-26-2017 at 01:56 PM. Reason: Added thought.
abninftr is online now   Reply With Quote
Old 02-26-2017, 02:10 PM   #5
cxm
 
cxm's Avatar
 
Join Date: May 2011
Location: Florida, CSA
Posts: 1,039
A 10 grain difference isn't a lot when you consider how small a grain is... 1/7000 of a pound...

Maybe it would make a difference at absolute max loads, but I don't load as hot as possible anyway... fact is the hottest possible load is seldom the most accurate load...

10% below max is likely to be a good load for most shooting.

FWIW

Chuck
__________________
Hoist On High The Bonny Blue Flag That Bears The Single Star!

Fear God and Dreadnought!!

You can't miss fast enough to win a gun fight!
cxm is offline   Reply With Quote
Old 02-28-2017, 09:34 AM   #6
Member
 
Join Date: Oct 2010
Posts: 28
Gee, is your worry was important, the reloading manuals would cover weighing and sorting the cases.
You are confusing the games that precision long-range rifle shooters use, generally without any verification that it matters and is just a "consistency always improves accuracy" justification, with a gun that is lucky to shoot 12 MOA. I find .40S&w is more temperamental than other cartridges, but find no difference in mixed cases.
Read and follow the directions in the loading manual and stop looking for non-existent problems.
Otherwise, just live with sorting all cases by weight and loading, if that will make you feel better.
noylj is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -5. The time now is 05:34 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
SEO by vBSEO ©2011, Crawlability, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.