Mixed headstamp vs single.

[AJC1]

Picked up a batch of 250 223 rounds from dads house all loaded the same with 75 grain hornaday hpbt bullets over tac. My loading seems to be more about mad scientist testing than shooting so I plan to sort by headstamp and test brass and single vs mixed headstamp in my target gun. Should I run 5 shot groups and try to complete most of the test or ten shot groups over many days. It's a compromise either way but I'm doing it for fun and posterity. The lot is mixed brass so when I get home it's going to start by hours of sorting.

 

[Sofie007]

Good practices for rational subgrouping:
1. Arrange your subgroups so as to capture as little variation as possible within subgroups. [A subgroup is a group with all one factor, in your Case "headstamp". What you talking about (i.e. groups of five) that is considered a “subgroup” size.] To do this, you may have to e.g. weigh each case to get as little variation for each individual subgroup, or make sure they are all the same trim length WITHIN EACH INDIVIDUAL subgroup.
2. Run your different subgroups (during your trials) to capture the MOST variation between subgroups. Determine what factors are going to determine the most variation" (e.g. cold Barrel versus warm/hot Barrel, cleanbore versus fouled). You can block these factors bye doing your trials before they have a chance to change. For example run all your treatments with a cold Barrel before it has a chance to heat up. In past practice, a cold Barrel versus a hot Barrel will have a big factor on where the point of impact is.
Remember during experiments, there is always bias; either conscious or unconscious. So if you know what each group comprises (that is, what headstamp is from that subgroup), you may subconsciously force one to be better or worse. Good luck.

 

[bluejay75]

You will need a baseline. So either work the load in mixed and proof against one or work the load in one and proof against mixed.

May even be worthwhile to make sure your mix has a sampling of low, high and mid range capacities. The better you set your parameters the less resources you will expend.

I’m too short on almost everything for long tests these days.

 

[GeoDudeFlorida]

Good practices for rational subgrouping:
1. Arrange your subgroups so as to capture as little variation as possible within subgroups. [A subgroup is a group with all one factor, in your Case "headstamp". What you talking about (i.e. groups of five) that is considered a “subgroup” size.] To do this, you may have to e.g. weigh each case to get as little variation for each individual subgroup, or make sure they are all the same trim length WITHIN EACH INDIVIDUAL subgroup.
2. Run your different subgroups (during your trials) to capture the MOST variation between subgroups. Determine what factors are going to determine the most variation" (e.g. cold Barrel versus warm/hot Barrel, cleanbore versus fouled). You can block these factors bye doing your trials before they have a chance to change. For example run all your treatments with a cold Barrel before it has a chance to heat up. In past practice, a cold Barrel versus a hot Barrel will have a big factor on where the point of impact is.
Remember during experiments, there is always bias; either conscious or unconscious. So if you know what each group comprises (that is, what headstamp is from that subgroup), you may subconsciously force one to be better or worse. Good luck.

Pretty much covered it except to make sure you account for atmospheric condition. Don’t forget to account for your own day to day variations, too. I know how hard it is to be completely subjective but in the end it will pay off.
By the time you’re done testing and getting everything documented it will be so much easier to adjust for powder and bullet lot changes.

 

[edwardware]

2 days, 5 shot groups, opposite order on the subsequent day.

Repeat in the opposite-opposite order on the opposite days of the lunar cycle to confirm.

 

[AJC1]

You will need a baseline. So either work the load in mixed and proof against one or work the load in one and proof against mixed.

May even be worthwhile to make sure your mix has a sampling of low, high and mid range capacities. The better you set your parameters the less resources you will expend.

I’m too short on almost everything for long tests these days.

There is no real baseline here just comparing them to themselves. If remmington is .8 moa and pmc is 1.1 and I find that cases with similar volume give similar results in velosity that would be useful to me.this barrel is still technically in brake in as it has 140 ish total rounds ever. That adds in it's own variation. This is more like comparing factory loads as I didnt load or control any of the process. Trigger time with data collection.

 

[AzShooter1]

Separating by head stamp is very important to verify the accuracy of any load. Years ago I would pick up scrap brass at the range and shoot it. I learned that my groups could be much tighter so I settled on one brand of brass and stayed with it.

Weighing your loaded round will have no affect on the quality of the load. Weighing your components before you reload will make a big difference. I.E. cases can weigh as much as + or - 5 grains or more ruining any idea of getting good groups from that brass.

Good luck. Your experiment will prove a lot for you.

 

[lordpaxman]

Weighing your loaded round will have no affect on the quality of the load. Weighing your components before you reload will make a big difference.

If you didn’t weigh your components before reloading, you could at least weigh the brass after firing.
@AJC1 do you plan to chrono these rounds? While you’re looking for best groups, it would seem having this data might help explain a better grouping from a specific HS especially if it’s a velocity node.

 

[AJC1]

If you didn’t weigh your components before reloading, you could at least weigh the brass after firing.
@AJC1 do you plan to chrono these rounds? While you’re looking for best groups, it would seem having this data might help explain a better grouping from a specific HS especially if it’s a velocity node.

The goal is to chronograph them yes and looking for nodes was specifically part of my plan as you mentioned. Depending on whether any of the brass is military it might give me a wide velocity range between headstamps to give a peek

 

[bluejay75]

Depending on the load the military brass might give you faster velocities as they are going to compress the most and compress first. I do a lot of testing on the low side of brass capacity.

 

[Bfh_auto]

There is no real baseline here just comparing them to themselves. If remmington is .8 moa and pmc is 1.1 and I find that cases with similar volume give similar results in velosity that would be useful to me.this barrel is still technically in brake in as it has 140 ish total rounds ever. That adds in it's own variation. This is more like comparing factory loads as I didnt load or control any of the process. Trigger time with data collection.

Set up identical targets. Shoot round Robin in ascending order. Followed by descending after the barrel cools.
Overlay the impacts from each target on the other using a sharpie or pencil.

 

[AJC1]

Depending on the load the military brass might give you faster velocities as they are going to compress the most and compress first. I do a lot of testing on the low side of brass capacity.

When comparing lake city 223 to other 223 that is not a consistent trend. In 308 I find that more true. I believe that to be also true in 30-06 but I haven't spent any real dedicated time with that cartridge.