Vertical Dispersion - Weighing Primers

[skiutah02]

@MikeMcCasland, great set of questions. Primer sorting may be an option. Test sorted versus unsorted and see what happens.

Few other thoughts. Do you use a reliable chrono while testing? I ask as that would be a good way to determine if your ES is not as tight as it could be, which would point towards primer inconsistencies or your powder node being slightly off (for a 20 shot string an ES of 20 or less is ideal).

if your ES is tight, your challenge might be position related while firing, scope magnification/mirage issues, or seating depth issues.

If your ES is not ideal, you could examine your brass prep and/or do a simple test at LR.

Load up 3 rounds per charge weight, in .1 grain increments surrounding your current load. For example, if your current node was 50.3, then load 50.1, 50.2, 50.3, 50.4, 50.5. Shoot them round robin at 1,000 yards to see if any of them sing for you (keep same POA and measure vertical dispersion...don’t worry about horizontal).

From direct experience I can share that @dmoran helped me tremendously in identifying positive compensation at 1,000 yards by tweaking my node up or down by a single .1 grain charge. It works miracles to test this!

Let us know what you find.

^this

 

[Ledd Slinger]

No, but I may hit you up for some 215s lol.


Tom

Got any toilet paper and hand sanitizer to trade? Lol!

 

[Bc'z]

Just for fun I did an experiment in the loading room, while sorting some 205s.

Here's a light full, and a heavy full, being dissolved of their compound with water. Hint, it speeds up the process to shake it.
View attachment 1163625

Below is the dissolved primers drying.

View attachment 1163628

The next couple below are their empty weights.

View attachment 1163631

View attachment 1163632

Sample size of 2, lol but it does appear about 66% of the weight you're sorting is compound. The heavy one is normally not a cull in my lot, but towards the heavy end. The light one was WAY OUT, and the photo below might explain where it came from.

View attachment 1163633

This experiment is not indented to be scientific proof of anything, as I go about things by putting holes in paper for proof of anything I do or don't do.


Tom

I stopped by Mark's house on way back from range and seen this lil yellow spot in a empty package of federal primers today. That's twice this week I've seen this.
No he dont weigh, and yes he was loading for this evening's local 600 match. Oops!!

 

[Ledd Slinger]

Havent sorted SRPs at all yet, but just got through testing 320 of my GM215M's in light of some upcoming load testing I will be doing with the new Berger 245gr EOLs in my 300 NMI.

There was plenty of outliers from a 0.1gr window but not bad. Lot of variation in the sealant. Some packed with it to the gill, a handful that didnt have any sealant, and others everywhere in between. Not sure how bad that effects the sorting, but I'm sure it doesn't help anything.

Considering a 0.1gr window and only 320 primers sorted, that's about 90% consistency so I'm happy with that. The last box sorted had a lot less outliers than the first 2 boxes and 1 partial box so not sure what the consistency would be if I kept going to the full 1K? Maybe I'll get time to continue. Very interesting to see how many fliers I've experienced in the past on paper possibly could have been cause by the extreme outliers.

For my testing purposes with the new Berger 245gr EOLs, I will only be using the center weight node of primers from 5.62gr to 5.66gr.

 

[Rocketvapor]

Total range +/- 2%.

+/- of less than 1% captures most of that sample.

 

[whatwind?]

I had very similar results, but went in 02 gr increments

also, my spent primers were 4.90-5.00


FEd 215m
lot 2GGI78

of course the last primer I weighed was the lowest, this was about 270 primers, didn’t have any huge outliers

 

[sqrlgtr]

This thread was started by me last week. I'm not taking credit for the participation by any means, but it's one of the first where we've actually had a productive discussion on the topic. I searched this topic pretty extensively prior to creating, and noticed that in past threads it's a few folks who will talk about their experiences, followed by folks shouting them down saying it's not worth the time investment etc.

The issue with primer weight testing is that it's not going to result in some massive difference, hence why it's a debated topic (i.e. if it were obvious, everyone would be doing it).

I certainly welcome more to chime in with their experiences, but there are 4-5 folks in here who are doing it, and they're basically saying the same thing. It won't drastically alter you group, but it'll keep things more consistent.

Again, I don't know that it helps, but it seems to me it can't hurt. I was just loading them straight out of the box before.

Mike,
My bad I must of looked at join date instead of date post was started duh and yes I have enjoyed this thread.Again I apologize Mike.I will restate I do believe you can see the results of this especially with certain lots of primers that have a big difference in weight,plus you and your equipment has to be up to the task also.

 

[Ledd Slinger]

I had very similar results, but went in 02 gr increments

also, my spent primers were 4.90-5.00


FEd 215m
lot 2GGI78

of course the last primer I weighed was the lowest, this was about 270 primers, didn’t have any huge outliers

The primers I weighed have been on the shelf for years now. I picked up a new 1000 lot of 215M the other day. Gonna weigh them to see if results are similar .

 

[Jennb]

This thread was started by me last week. I'm not taking credit for the participation by any means, but it's one of the first where we've actually had a productive discussion on the topic. I searched this topic pretty extensively prior to creating, and noticed that in past threads it's a few folks who will talk about their experiences, followed by folks shouting them down saying it's not worth the time investment etc.

The issue with primer weight testing is that it's not going to result in some massive difference, hence why it's a debated topic (i.e. if it were obvious, everyone would be doing it).

I certainly welcome more to chime in with their experiences, but there are 4-5 folks in here who are doing it, and they're basically saying the same thing. It won't drastically alter you group, but it'll keep things more consistent.

Again, I don't know that it helps, but it seems to me it can't hurt. I was just loading them straight out of the box before.

Mike the best thing you can do is test it yourself. Never take anyones word for what may or may not help you. Find out for yourself!!

 

[Ned Ludd]

Just for fun I did an experiment in the loading room, while sorting some 205s.

Sample size of 2, lol but it does appear about 66% of the weight you're sorting is compound.

Tom

Tom - not sure I follow this. By my math, less than 10% of the total primer weight is priming compound (i.e. [weight after dissolving priming compound/weight before dissolving priming compound] x 100]. Are you referring to a percentage of total range of primer weights from high to low?

In any event, your experiment suggests another highly accurate approach to quantify the amount of priming compound in order to validate using a weight-based method. Specifically, anyone with access to a UV-Vis spectrophotometer could accurately compare the amount of priming compound using absorbance. Simply dissolve the priming compound for a few different weight-sorted primers in a specific volume of water, then measure the OD 410nm. By my spectrophotometric eye, the yellow color of dissolved priming compound in your plastic bottles will absorb very well at that wavelength. It's simply another way of directly and more accurately determining the concentration (i.e. amount per fixed volume of water) of priming compound, and one that doesn't depend on weighing anything before/after. Thus, it would be a good way to confirm or validate the use of a weight-based approach for estimating the amount of priming compound. Obviously, the primers tested this way would be lost, but it's simply a one-time experiment to compare with the results of weight-based sorting.

Mike - because you started this thread 20 days ago, I can only assume you are well along in the sorting process by now. My only advice is to pace yourself. The current "break from the ordinary" we are experiencing might last a while longer, so you probably don't want to sort all of them right away and then have to find something else to occupy your time.

 

[Rocketvapor]

I agree, pace yourself, but anyone that doesn't end up with sorted primers is just plain lazy
I've got peanut butter jars full of primed cases now but don't want to load them yet.

 

[dolek]

I agree, pace yourself, but anyone that doesn't end up with sorted primers is just plain lazy
I've got peanut butter jars full of primed cases now but don't want to load them yet.

Lazy?...or maybe smarter ?

 

[fyrewall]

Despite somewhat less than super precise weighing methods and showing results more precise than recorded, I still like the stuff in the attachment below because other factors or variables found in the loading process were eliminated. The primer blast waves were the only item measured and recorded.

https://arxiv.org/ftp/arxiv/papers/1102/1102.1644.pdf

Possibly, the group shapes or bullet holes are just vertically dispersed for reasons other than ammo characteristics - another variable.

 

[johara1]

Maybe it would boil down one thing .... sort everything ....... jim

 

[tom]

Tom - not sure I follow this.

I was looking at the difference between the two unmodified. Then the difference between the two with the compound dissolved. Since we are talking about sorting by weight, and a lot of times folks will ask what exactly of that weight difference is cup, anvil, compound....ect. So I just did this while I was working on the stuff one night. The difference was made 66% less different with the yellow stuff removed was how I saw it.


Tom

 

[whatwind?]

Despite somewhat less than super precise weighing methods and showing results more precise than recorded, I still like the stuff in the attachment below because other factors or variables found in the loading process were eliminated. The primer blast waves were the only item measured and recorded.

https://arxiv.org/ftp/arxiv/papers/1102/1102.1644.pdf

Possibly, the group shapes or bullet holes are just vertically dispersed for reasons other than ammo characteristics - another variable.

conclusion...
With mass sorting on a sufficiently fine scale, the experiment to determine whether primer strength or uniformity has the bigger effect on muzzle velocity variations is simple: prepare a group of test samples with both unsorted andsorted primers and compare their standard deviations from the mean muzzle velocities. If one obtains the same result for numerousloads, then confidence builds that the result will likely be the same for other loads as well. In contrast, it is also possible that some loads are more sensitive to primer uniformity than others, in which case it might not benot possible to know whethermass sorting of primers will benefit a specific load until it is tried for that load.

 

[fyrewall]

I see your point actual velocity measuring and comparisons between weight sorted and just dumped out of the box with equal and reasonably uniform components and assembly

Why I like the attachment is that I have better things to do than weigh primers and run extensive velocity comparisons for my requirements. I am not a bench rest shooter and more than adequate results using primers having established high quality ratings is sufficient.

Would primers having uniform blast pressures be likely to produce uniform velocities?

Despite my causal approach to primer weight variations some of my extreme velocity spreads measure less than 15 fps. I think the actual group shape, like vertical spread, would be more important for long range results and that should also be considered

The attachment to me is a sensible way to determine primer quality bypassing variations introduced by the loading process.

 

[Joe Salt]

Look if you don't want to spend time Weighing them then don't. But you have a lot of time on your hands right now so go try it, you might like it.

Joe salt

 

[Alex Wheeler]

Its not as simple as velocity. Poor primer ignition will kill accuracy or cause fliers that wont show up in velocity. I know that from working on ignitions and fixing poor shooting rifles. Changes in the pressure curve may change exit time without changing speed. The only way to test for yourself is to shoot groups at the distance you will compete imo. If you just look for velocity changes you may not see the whole picture.

 

[dmoran]

The velocity variations between primers attribute to very small amounts of velocity in terms of the actual velocity, that is easily "lost in the noise" of the ammo's own standard deviations and the chronographs error factors. Sort to speak, if the ammo used has an SD of 5-fps and the chronograph has an error factor of 3-fps, for a total of 8-fps deviation error, the primers being tested would have to have more then 8-fps ES of variation to not get "lost in the noise". Ballistically, 8-fps can easily attribute to 3" of bullet path variation at 1000yds with popular calibers & bullet combinations that are commonly used at 1000yd competitions. Hence, why primer induced fliers are more easily seen on the target, then within the velocity data - IME.