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Max Online: 16728 @ 03/25/12 08:51 AM
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#7210505 - 06/27/18 10:06 PM Case weight
68A Online   content
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Registered: 09/29/12
Posts: 2919
Loc: North Texas
Have some Hornady brass, same headstamp, different lots, once fired. Never been one to weight sort but noticed today there was up to 30 gr difference between loaded rounds. Anyone have any guesses on if I might see descrepancies down range? Powder charges were weighed twice for accuracy so I know everything is dead on there.

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#7210522 - 06/27/18 10:24 PM Re: Case weight [Re: 68A]
patriot07 Offline
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Registered: 11/06/11
Posts: 2537
Loc: Royse City, TX
30 grains? Goodness, that's hard to believe. I have no input, but I'm interested to hear the comments.

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#7210529 - 06/27/18 10:31 PM Re: Case weight [Re: patriot07]
68A Online   content
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Registered: 09/29/12
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Loc: North Texas
Originally Posted By: patriot07
30 grains? Goodness, that's hard to believe. I have no input, but I'm interested to hear the comments.


Find it hard to believe myself. Not sure where else the weight difference would come from. Same box of primers and bullets. Leaves me scratching my head. I could understand a few grains but 30 is a far stretch.

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#7210626 - 06/28/18 06:49 AM Re: Case weight [Re: 68A]
GLC Online   content


Registered: 02/25/09
Posts: 5077
Loc: BenBrook Texas
Strangely enough I have been looking at the same thing lately chasing a load. I have some Winchester 7mm08 brass that has a range from 152 to 165 grains. Not a 30 grain difference but even this small amount of 13 grains does impact the POI on loads. Now this is bare brass only, not loaded. I do believe the variance is from number of reloads on each piece of brass. The more times you load, the brass flows forward, and trim, the lighter they become so I am guessing the case volume also increases which probably effects case pressure?
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#7210640 - 06/28/18 07:11 AM Re: Case weight [Re: 68A]
kmon1 Online   content
junior

Registered: 09/27/06
Posts: 23486
Loc: Texas
Measure the case water capacity. Weigh an empty case then fill it with water and weigh again.

Your case is your combustion chamber the less room with a given load the higher the pressure and there is a correlation between case volume and pressure with given load. Different pressure different velocity.
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#7210674 - 06/28/18 08:01 AM Re: Case weight [Re: GLC]
68A Online   content
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Registered: 09/29/12
Posts: 2919
Loc: North Texas
Originally Posted By: GLC
Strangely enough I have been looking at the same thing lately chasing a load. I have some Winchester 7mm08 brass that has a range from 152 to 165 grains. Not a 30 grain difference but even this small amount of 13 grains does impact the POI on loads. Now this is bare brass only, not loaded. I do believe the variance is from number of reloads on each piece of brass. The more times you load, the brass flows forward, and trim, the lighter they become so I am guessing the case volume also increases which probably effects case pressure?


This was my thinking as well but 30 gr would be extreme. So I pulled two bullets from each weight extreme this morning and measured powder, bullet and case. Case was the difference. So, looked at my headstamp on both. Appears my 4 yr old had some fun mixing up my bags of brass. I had a bunch of hornady match sorted from other hornady. Important to note here I am not a horrible father, he does not have access to powder or primers, I keep them locked up separately. Another reminder to triple check brass.

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#7210689 - 06/28/18 08:21 AM Re: Case weight [Re: 68A]
GLC Online   content


Registered: 02/25/09
Posts: 5077
Loc: BenBrook Texas
Originally Posted By: 68A
Originally Posted By: GLC
Strangely enough I have been looking at the same thing lately chasing a load. I have some Winchester 7mm08 brass that has a range from 152 to 165 grains. Not a 30 grain difference but even this small amount of 13 grains does impact the POI on loads. Now this is bare brass only, not loaded. I do believe the variance is from number of reloads on each piece of brass. The more times you load, the brass flows forward, and trim, the lighter they become so I am guessing the case volume also increases which probably effects case pressure?


This was my thinking as well but 30 gr would be extreme. So I pulled two bullets from each weight extreme this morning and measured powder, bullet and case. Case was the difference. So, looked at my headstamp on both. Appears my 4 yr old had some fun mixing up my bags of brass. I had a bunch of hornady match sorted from other hornady. Important to note here I am not a horrible father, he does not have access to powder or primers, I keep them locked up separately. Another reminder to triple check brass.


Yep, found the same thing one time, some of my Remington mixed with Winchester.
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#7210757 - 06/28/18 09:22 AM Re: Case weight [Re: 68A]
ChadTRG42 Online   happy
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Registered: 09/16/09
Posts: 13503
Loc: Lewisville, TX
If it's different lots, then it's a different mfg time, which can easily lead to different weights. If one lot was 30 grains, that would be BAD!! This is why I don't recommend mixing different lots of brass. And you can not weigh loaded rounds. Way to many variable differences between the brass case, powder charge and bullet weight. I had a customer weigh out some of my "match" grade loaded ammo and posted on a forum that I had bad weight tolerances with a few grains spread weighing the loaded ammo. It doesn't work that way.

I have weighed out some Hornady brass, and I can easily see about 6-8 grain spread on the same lot. Go to my Norma cases, and they are about 1.5 to 2 grain spread. I order in my 300 WM brass in bulk with Hornady and Norma brass. I can weigh as many as I want, and I will weight sort my Norma 300 Win Mag brass for my 7mm-300 Win Mag rifle. I have them within .5 grain.
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#7210764 - 06/28/18 09:28 AM Re: Case weight [Re: 68A]
RiverRider Offline
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Registered: 11/11/07
Posts: 8223
Loc: Wise Co.
Someone gave me about 70 fired 6mm cases a while back, all R-P headstamps. I could find three minor variations of the headstamp, presumably made at different times. I saw over 20 grains of variation in case weight.

Then I bought brand new brass.
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#7210808 - 06/28/18 10:05 AM Re: Case weight [Re: ChadTRG42]
68A Online   content
Veteran Tracker

Registered: 09/29/12
Posts: 2919
Loc: North Texas
Originally Posted By: ChadTRG42
If it's different lots, then it's a different mfg time, which can easily lead to different weights. If one lot was 30 grains, that would be BAD!! This is why I don't recommend mixing different lots of brass. And you can not weigh loaded rounds. Way to many variable differences between the brass case, powder charge and bullet weight. I had a customer weigh out some of my "match" grade loaded ammo and posted on a forum that I had bad weight tolerances with a few grains spread weighing the loaded ammo. It doesn't work that way.

I have weighed out some Hornady brass, and I can easily see about 6-8 grain spread on the same lot. Go to my Norma cases, and they are about 1.5 to 2 grain spread. I order in my 300 WM brass in bulk with Hornady and Norma brass. I can weigh as many as I want, and I will weight sort my Norma 300 Win Mag brass for my 7mm-300 Win Mag rifle. I have them within .5 grain.


Thanks for the advice, Chad. Iím not in the habit of weighing loaded cases because as you said, way to many variables, and Iíve come to learn even the most precise rounds will have weight variations. It just so happened on this batch I had a couple suspect rounds after my funnel dropped some powder outside a case and I identified which one it was by weighing the two rounds. Thatís how I can across the extreme weight variation.

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