Should you work up a new load using virgin brass?

Major Dave (retired) · August 21, 2009, 07:12 PM

I'm about 3/4 through working up a new load for my rifle, and as I get ever nearer the MAX load shown in the manual, I suddenly thought -

"Wait a minute; I bet they didn't derive this pressure tested MAX using virgin brass. Once fired brass would have greater internal volume than virgin brass, because it has been fire formed to fit the chamber, and therefore can accept a higher charge of powder."

True/false?

I'm thinking I better stay a couple of grains below MAX, until I get some brass fire formed to my rifle chamber.

What do you think?

Kyo · August 21, 2009, 07:14 PM

why don't you start at the starting load like every manual ever says?

Gun 4 Fun · August 21, 2009, 07:15 PM

Most loads in the manuals are worked up in fully resized brass, so the new vs. fireformed issue, isn't a factor.

SL1 · August 21, 2009, 07:40 PM

then I don't think it makes much difference whether you use new brass or pre-fired brass (once or more than once).

The idea of measuring the volume of a fired case is to figure-out how big YOUR chamber is. The brass expands until the chamber stops it, and I don't think it makes much difference in peak pressure whether the brass starts at the chamber wall (i.e., neck-sized) or a few hundredths away (full-length sized).

If you ARE measuring head expansion, tell us and I will explain the comment.

SL1

Major Dave (retired) · August 22, 2009, 06:27 PM

I didn't say I started at 3/4 up between Min and Max load.

Let me clarify - I started at Min reloading manual load, and have worked up thru 4 intermediate loads, and now am about 3/4 of the way to the Max listed load.

OK?

Kyo · August 22, 2009, 06:44 PM

sorry about the confusion. manufacturers load their ammo to max specs, and that is virgin brass. so, it should be fine either way.

GP100man · August 22, 2009, 09:49 PM

for rifle laddering i prepare a batch of brass & hopefully before i use it up i have a load that the rifle likes.

me&my308 · August 24, 2009, 03:09 PM

Yes.....there is a diff. I just ran into the same issue. Worked up loads for .308 using virgin Lapua Brass.....I fired 300 to get all fire formed cases then just neck sized....all else being the same, the neck sized pre-fired brass gives a different fps.

Brian Pfleuger · August 24, 2009, 03:14 PM

Quote:

.all else being the same, the neck sized pre-fired brass gives a different fps.

Are you sure all else was the same. (atmospheric conditions...)

(Just asking, no offense)

me&my308 · August 24, 2009, 03:19 PM

Are you sure all else was the same. (atmospheric conditions...)

(Just asking, no offense)

Good point......no, atmospheric conditions were not the same although similar, at least temperature.

Brian Pfleuger · August 24, 2009, 03:25 PM

Well, I think that the temperature difference would have to be fairly significant to make a statistically significant difference in MV. So, you're probably right. I believe Sierra claims 1 fps per degree Fahrenheit.

GeauxTide · August 24, 2009, 08:28 PM

Not a true/false question. I always try to see if new brass will chamber without sizing. If so, then I just neck size to get the proper bullet tension. Then the case is perfect for my chamber. My interpretation of maximum for my rifle, case, powder, bullet, primer combo is the head expansion of .005 greater than SAAMI specs. After that point, I've experienced the standard pressure signs on primers, extraction, etc. FYI, the five calibers that I load in the 308/30-06 family don't give the best accuracy with maximum loads. Only one that gives me the best accuracy at the top is the 7mm RM.

SL1 · August 25, 2009, 07:39 AM

GeauxTide,

You said you are looking for 0.005" of case head expansion as a pressure limit.

Did you mean 0.0005". Or are you really measuring the expansion ring (on the case wall in front of the web a ways) instead of the head (solid part of the case between the web and extractor groove, with only the flash hole going through it)?

I ask because others are probably reading this and looking for ideas to use themselves. Case head expansion of 0.005" would be WAY too much. Pressure ring expansion depends on YOUR chamber dimensions and its change from SAAMI specs means nothing from gun-to-gun.

SL1

August 21, 2009, 07:12 PM	#1
Major Dave (retired) Senior Member Join Date: March 12, 2008 Location: Between Dallas and Shreveport, LA Posts: 569	Should you work up a new load using virgin brass? I'm about 3/4 through working up a new load for my rifle, and as I get ever nearer the MAX load shown in the manual, I suddenly thought - "Wait a minute; I bet they didn't derive this pressure tested MAX using virgin brass. Once fired brass would have greater internal volume than virgin brass, because it has been fire formed to fit the chamber, and therefore can accept a higher charge of powder." True/false? I'm thinking I better stay a couple of grains below MAX, until I get some brass fire formed to my rifle chamber. What do you think? __________________ Artillery lends dignity to what would otherwise be but a vulgar brawl.

August 21, 2009, 07:15 PM	#3
Gun 4 Fun Senior Member Join Date: November 3, 2008 Posts: 956	Most loads in the manuals are worked up in fully resized brass, so the new vs. fireformed issue, isn't a factor. __________________ S&WCA member NRA member NAHC Life member

August 21, 2009, 07:40 PM	#4
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	If you aren't measuring head expansion then I don't think it makes much difference whether you use new brass or pre-fired brass (once or more than once). The idea of measuring the volume of a fired case is to figure-out how big YOUR chamber is. The brass expands until the chamber stops it, and I don't think it makes much difference in peak pressure whether the brass starts at the chamber wall (i.e., neck-sized) or a few hundredths away (full-length sized). If you ARE measuring head expansion, tell us and I will explain the comment. SL1

August 22, 2009, 06:27 PM	#5
Major Dave (retired) Senior Member Join Date: March 12, 2008 Location: Between Dallas and Shreveport, LA Posts: 569	Reply to Kyo I didn't say I started at 3/4 up between Min and Max load. Let me clarify - I started at Min reloading manual load, and have worked up thru 4 intermediate loads, and now am about 3/4 of the way to the Max listed load. OK? __________________ Artillery lends dignity to what would otherwise be but a vulgar brawl.

August 22, 2009, 09:49 PM	#7
GP100man Senior Member Join Date: August 1, 2007 Location: Tabor City , NC. Posts: 1,969	for rifle laddering i prepare a batch of brass & hopefully before i use it up i have a load that the rifle likes. __________________ GP100man

August 21, 2009, 07:14 PM	#2
Kyo Senior Member Join Date: April 14, 2009 Posts: 897	why don't you start at the starting load like every manual ever says?

August 22, 2009, 06:44 PM	#6
Kyo Senior Member Join Date: April 14, 2009 Posts: 897	sorry about the confusion. manufacturers load their ammo to max specs, and that is virgin brass. so, it should be fine either way.

August 24, 2009, 03:09 PM	#8
me&my308 Junior Member Join Date: July 23, 2009 Location: Atlanta, GA Posts: 13	Yes.....there is a diff. I just ran into the same issue. Worked up loads for .308 using virgin Lapua Brass.....I fired 300 to get all fire formed cases then just neck sized....all else being the same, the neck sized pre-fired brass gives a different fps.

August 24, 2009, 03:19 PM	#10
me&my308 Junior Member Join Date: July 23, 2009 Location: Atlanta, GA Posts: 13	Are you sure all else was the same. (atmospheric conditions...) (Just asking, no offense) Good point......no, atmospheric conditions were not the same although similar, at least temperature.

August 24, 2009, 03:25 PM	#11
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	Well, I think that the temperature difference would have to be fairly significant to make a statistically significant difference in MV. So, you're probably right. I believe Sierra claims 1 fps per degree Fahrenheit. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

August 24, 2009, 08:28 PM	#12
GeauxTide Senior Member Join Date: April 20, 2009 Location: Helena, AL Posts: 4,425	Not a true/false question. I always try to see if new brass will chamber without sizing. If so, then I just neck size to get the proper bullet tension. Then the case is perfect for my chamber. My interpretation of maximum for my rifle, case, powder, bullet, primer combo is the head expansion of .005 greater than SAAMI specs. After that point, I've experienced the standard pressure signs on primers, extraction, etc. FYI, the five calibers that I load in the 308/30-06 family don't give the best accuracy with maximum loads. Only one that gives me the best accuracy at the top is the 7mm RM.

August 25, 2009, 07:39 AM	#13
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	GeauxTide, You said you are looking for 0.005" of case head expansion as a pressure limit. Did you mean 0.0005". Or are you really measuring the expansion ring (on the case wall in front of the web a ways) instead of the head (solid part of the case between the web and extractor groove, with only the flash hole going through it)? I ask because others are probably reading this and looking for ideas to use themselves. Case head expansion of 0.005" would be WAY too much. Pressure ring expansion depends on YOUR chamber dimensions and its change from SAAMI specs means nothing from gun-to-gun. SL1