Load development brass question

[Savagehunter]

When I load my powder charge work up going from low to high does the differing charges expand my brass to different percentage of fire formed. Say I start at 49 gr and work up to 52.5 gr of powder is the brass at the top of the powder charge expanded a lot more than the lowest charge. And when I go to resize do those differing dimensions affect my consistency as far as shoulder bump trim length and powder capacity?

 

[std7mag]

49-52 grains of powder shouldn't make much difference on how your brass turns out.

Of course this doesn't tell us the cartridge, and respective case volume.

I form my AI brass with known accurate standard cartridge loads.

 

[dgeesaman]

When I load my powder charge work up going from low to high does the differing charges expand my brass to different percentage of fire formed. Say I start at 49 gr and work up to 52.5 gr of powder is the brass at the top of the powder charge expanded a lot more than the lowest charge. And when I go to resize do those differing dimensions affect my consistency as far as shoulder bump trim length and powder capacity?

Of course it depends. If it’s Hornady brass vs Lapua the brass will flow differently.

Get out the dial calipers and see the results.

David

 

[Texas10]

When starting out with new brass, I expect it will take several load cycles before the brass is fully fireformed, and typically I do not FL size until I begin to experience a stiff bolt drop. Once at that point I know the brass is fully formed and can then bump back the shoulder .002 or so to get good chambering and good consistent case volume. During this time I typically see brass shrink in OAL as the case expands.

On my 223 brass, I rarely FL size, preferring to neck size only with occasional annealing.

 

[Savagehunter]

So the measurements are what made me bring this up. After one firing the higher powder loads brass measure slightly different after the second firing I figure it's time to bump the shoulder but if I bump .002 on the longest I dont bump the shoulder on the shortest and that is confusing me as the 3rd time firing the brass has different levels of work. I measured my chamber so I have left trim length out til this firing and some of the brass hasn't reached what I determined would be my max trim length to help preserve the throat. Do I trim some and let the others try and catch up. My main concern is inconsistent brass from the start affecting accuracy. Stock savage long range hunter. 167 rnds. Down the barrel. 52.5 gr of 4831sc loaded to the lans 2891 avg velocity. 143gr eldx I also worked up berger hvld 140 gr accuracy was identical so I went with the cheaper bullet. Am I overthinking this?

 

[Gabe22BR]

So the measurements are what made me bring this up. After one firing the higher powder loads brass measure slightly different after the second firing I figure it's time to bump the shoulder but if I bump .002 on the longest I dont bump the shoulder on the shortest and that is confusing me as the 3rd time firing the brass has different levels of work. I measured my chamber so I have left trim length out til this firing and some of the brass hasn't reached what I determined would be my max trim length to help preserve the throat. Do I trim some and let the others try and catch up. My main concern is inconsistent brass from the start affecting accuracy. Stock savage long range hunter. 167 rnds. Down the barrel. 52.5 gr of 4831sc loaded to the lans 2891 avg velocity. 143gr eldx I also worked up berger hvld 140 gr accuracy was identical so I went with the cheaper bullet. Am I overthinking this?

Yes, your over thinking!!!

bump your shoulders-.003”-.004” back
Trim when needed, it’s factory barrel??
Just b/c you read it on here somewhere, doesn’t mean it applies to your situation...

 

[Savagehunter]

Got it bump em back .004 kind of a restart now all the loads are 52.5 gr growth should stay pretty equal trim when they reach max and I'm good to go.

 

[Ned Ludd]

Do you think the brass perceives a big difference between 55,000 psi and 60,000 psi?

 

[Jeffrey Tooker]

Do you think the brass perceives a big difference between 55,000 psi and 60,000 psi?

The question you ask is very general. I have found that SRP case heads (primer pockets) are able to stand more pressure than LRP case heads. Case in point:
Lapua first made 260 Rem cases in LRP. With stiff loads the primer pockets failed
in three or four re loads. They then started making the cases with SRP. Durability
went way up. There are different alloys of brass. Some are harder than others.
The softer the brass the easier it will flow. Brass flow in a cartridge case usually
(under normal pressures) flows into the neck of the case. When there is enough flow case length trimming is required. The brass that flows into the neck comes from the web of the case. When too much brass has flowed you get case head separation. One of the first indications of unsafe pressure is shiny spots on the fired case head.
Always look at your fired brass for indications of excessive pressure. Reading your brass for pressure signs is a whole other topic. Each rifle is different, If you have indications on your fired brass that pressure is too high, do what the brass tells you. The re loading manual is a general guide line. This is why you start low and work up, watching your brass as you go. At much higher than safe pressures brass will flow into the bolt head, usually the extractor groove. Generally the softer the brass the easier it will flow, or be affected by pressure. Just by definition higher pressure will stress the brass more than lower pressure. The best and most durable brass I have found is Lapua.

Jeffrey

 

[Ned Ludd]

The question you ask is very general. I have found that SRP case heads (primer pockets) are able to stand more pressure than LRP case heads. Case in point:
Lapua first made 260 Rem cases in LRP. With stiff loads the primer pockets failed
in three or four re loads. They then started making the cases with SRP. Durability
went way up. There are different alloys of brass. Some are harder than others.
The softer the brass the easier it will flow. Brass flow in a cartridge case usually
(under normal pressures) flows into the neck of the case. When there is enough flow case length trimming is required. The brass that flows into the neck comes from the web of the case. When too much brass has flowed you get case head separation. One of the first indications of unsafe pressure is shiny spots on the fired case head.
Always look at your fired brass for indications of excessive pressure. Reading your brass for pressure signs is a whole other topic. Each rifle is different, If you have indications on your fired brass that pressure is too high, do what the brass tells you. The re loading manual is a general guide line. This is why you start low and work up, watching your brass as you go. At much higher than safe pressures brass will flow into the bolt head, usually the extractor groove. Generally the softer the brass the easier it will flow, or be affected by pressure. Just by definition higher pressure will stress the brass more than lower pressure. The best and most durable brass I have found is Lapua.

Jeffrey

The question I asked was rhetorical, not general. The OP specifically asked whether cases fired over a range of 49 to 52.5 gr powder had undergone a sufficient pressure differential to noticeably alter their external dimensions AFTER re-sizing. The answer is: not likely. The OP was not asking about the negative effects of loads close to, or exceeding MAX pressure. Of course those effects occur, and there are a wide range of variables that figure into those effects, such as shoulder angle, the size of any relatively unsupported regions under the casehead (i.e. extractor), etc. In any event, if someone is concerned about the effect of a charge weight test pressure differential on their brass, the easiest way to find out whether it is a concern is by taking exacting measurements of a sufficient number of cases over several firings, as well as after re-sizing. If you can't measure the difference, it's probably not worth worrying about. The same holds true for brass that has been subjected to overpressure loads. Measurements of such brass will usually answer most questions that might arise as a result of its histroy.

I would add that the brass that flows into the neck is not coming from the webbing. To do so it would have to move almost 75% of the length of the case, which is not likely. It comes from the shoulder and base of the neck, and a sharper shoulder angle is often sufficient to minimize the effect. The underlying cause of casehead separation is that the region where the webbing thins out into the case wall represents an inherent weak spot in the case. Further, if the cases are annealed regularly, the case walls will remain quite malleable above a point that is actually well below the shoulder. Repeated lengthwise expansion and contraction of the case during firing and re-sizing naturally concentrates its effect on the inherently weak region just above the casehead where the brass thins out.

I specifically phrased the question the way I did so that hopefully, the OP would think about the malleability of brass and whether the pressure differential between 55,000 psi and 60,000 psi, or even 62,500 psi, was enough to make a noticeable difference in how much the cases expanded to fit the chamber [i.e. pressure cell]; and whether that difference would still remain after the re-sizing process. Sometimes cases may take as much as 2 or 3 firings to fully expand to fit the pressure cell, especially if low-pressure fire-forming loads are used. However, the expansion observed after the first firing would typically be only a fraction of that observed on the first firing. In other words, even the low end charge weight would represent a pressure differential of 50,000+ psi, which is at least 5 to 10 times greater than would likely be observed over the range of a typical charge weight test.

 

[243winxb]

I would set the shoulder bump on the case with the longest head to datum measurement. Let the rest grow to maximum.

There is a difference in case volume when comparing new brass to fired sized brass. Its about 1/4" difference in group size @ 100 yds . (243Win.) Factory brass right out of the box producing the bigger 100 yd groups.

Trim length- follow SAAMI maximums. Measureing the chamber length is ok to know, but trim lengths longer then SAAMI standards removes the "Safety zone" built into the chamber.
Crimping rounds in the chamber may take a gun apart.
I maintain the maxinum, never shorter.

Always check trim length after triming. Trimmers (WFT) that work off the shoulder/index, may get brass chips in the case holder. Brass will not get trimmed correctly.

 

[Jeffrey Tooker]

The question I asked was rhetorical, not general. The OP specifically asked whether cases fired over a range of 49 to 52.5 gr powder had undergone a sufficient pressure differential to noticeably alter their external dimensions AFTER re-sizing. The answer is: not likely. The OP was not asking about the negative effects of loads close to, or exceeding MAX pressure. Of course those effects occur, and there are a wide range of variables that figure into those effects, such as shoulder angle, the size of any relatively unsupported regions under the casehead (i.e. extractor), etc. In any event, if someone is concerned about the effect of a charge weight test pressure differential on their brass, the easiest way to find out whether it is a concern is by taking exacting measurements of a sufficient number of cases over several firings, as well as after re-sizing. If you can't measure the difference, it's probably not worth worrying about. The same holds true for brass that has been subjected to overpressure loads. Measurements of such brass will usually answer most questions that might arise as a result of its histroy.

I would add that the brass that flows into the neck is not coming from the webbing. To do so it would have to move almost 75% of the length of the case, which is not likely. It comes from the shoulder and base of the neck, and a sharper shoulder angle is often sufficient to minimize the effect. The underlying cause of casehead separation is that the region where the webbing fairly rapidly thins out into the case wall represents an inherent weak spot in the case. Further, if the cases are annealed regularly, the case walls will remain quite malleable above a point that is actually well below the shoulder. Repeated lengthwise expansion and contraction of the case during firing and re-sizing naturally concentrates its effect on the inherently weak region just above the casehead where the brass thins out.

I specifically phrased the question the way I did so that hopefully, the OP would think about the malleability of brass and whether the pressure differential between 55,000 psi and 60,000 psi, or even 62,500 psi, was enough to make a noticeable difference in how much the cases expanded to fit the chamber [i.e. pressure cell]; and whether that difference would still remain after the re-sizing process. Sometimes cases may take as much as 2 or 3 firings to fully expand to fit the pressure cell, especially if low-pressure fire-forming loads are used. However, the expansion observed after the first firing would typically be only a fraction of that observed on the first firing. In other words, even the low end charge weight would represent a pressure differential of 50,000+ psi, which is at least 5 to 10 times greater than would likely be observed over the range of a typical charge weight test.

The question I asked was rhetorical, not general. The OP specifically asked whether cases fired over a range of 49 to 52.5 gr powder had undergone a sufficient pressure differential to noticeably alter their external dimensions AFTER re-sizing. The answer is: not likely. The OP was not asking about the negative effects of loads close to, or exceeding MAX pressure. Of course those effects occur, and there are a wide range of variables that figure into those effects, such as shoulder angle, the size of any relatively unsupported regions under the casehead (i.e. extractor), etc. In any event, if someone is concerned about the effect of a charge weight test pressure differential on their brass, the easiest way to find out whether it is a concern is by taking exacting measurements of a sufficient number of cases over several firings, as well as after re-sizing. If you can't measure the difference, it's probably not worth worrying about. The same holds true for brass that has been subjected to overpressure loads. Measurements of such brass will usually answer most questions that might arise as a result of its histroy.

I would add that the brass that flows into the neck is not coming from the webbing. To do so it would have to move almost 75% of the length of the case, which is not likely. It comes from the shoulder and base of the neck, and a sharper shoulder angle is often sufficient to minimize the effect. The underlying cause of casehead separation is that the region where the webbing fairly rapidly thins out into the case wall represents an inherent weak spot in the case. Further, if the cases are annealed regularly, the case walls will remain quite malleable above a point that is actually well below the shoulder. Repeated lengthwise expansion and contraction of the case during firing and re-sizing naturally concentrates its effect on the inherently weak region just above the casehead where the brass thins out.

I specifically phrased the question the way I did so that hopefully, the OP would think about the malleability of brass and whether the pressure differential between 55,000 psi and 60,000 psi, or even 62,500 psi, was enough to make a noticeable difference in how much the cases expanded to fit the chamber [i.e. pressure cell]; and whether that difference would still remain after the re-sizing process. Sometimes cases may take as much as 2 or 3 firings to fully expand to fit the pressure cell, especially if low-pressure fire-forming loads are used. However, the expansion observed after the first firing would typically be only a fraction of that observed on the first firing. In other words, even the low end charge weight would represent a pressure differential of 50,000+ psi, which is at least 5 to 10 times greater than would likely be observed over the range of a typical charge weight test.

Point taken. However my objective was different from yours. There are those on this forum who are rather new to reloading. We who have been reloading for some time may sometimes forget that the newer people may not have had all of the experiences we have had. I felt that it was a good opportunity to bring up a few points about brass that might be of interest to some on this forum. That you and I should differ on some points inherent to any discussion of a detailed subject. Thank you for your input.

Jeffrey