Factory ammo vs reloads weight differences

[IA_shooter]

I guess I was bored today and I'm sure this has been discussed before at some point but I'll let you know what I found anyway.

Let me start by saying I weighed 10 random pieces in every sample.

I started by weighing same yr LC 223 brass and found about a max spread of 1.2gr in LC 10 and 1.1gr in some LC 14. I then weighed some once fired 22-250 brass that was cleaned but not processed and it had a max weight difference of 1.4 gr. and then I weighed some once fired but processed Prime 6.5 CM brass and found about the same weight difference.

So I then decided to start weighing my reloads vs factory loads and taking into account the 1.0-1.5gr difference in just the brass I wanted to see how factory ammo compared to my own loads. I won't get into specifics, but I weighed 2 different batches of my 223 loads, 2 batches of my 22-250 loads, and a batch of my 6.5 Creedmoor loads and found a MAX spread of between 1.2gr to 1.7gr of my own loaded ammo so I assume most of that weight difference is strictly in the brass weight differences.

I then weighed 3 different 223 factory loads, one 204 Ruger factory load, and 3 different 22-250 factory loads.

I was finding anywhere from 1.4gr to 3.9gr differences in factory ammo. The Frontier 223 55gr HP Match had the lowest spread, but everything else had double or more the difference in weights. There was a 3.9gr difference in some 204 Ruger factory ammo which surprised me to see that much of a difference in a smaller case like that. 2 of the 3 different 22-250 factory loads I weighed were within about 2.5 -2.7gr, but one was almost 3.5gr. and I suppose that's why that last factory load was the least accurate out of my 22-250 and the other two were about the same and pretty decent for accuracy.

At any rate, I just found this interesting today and thought maybe some of you would too. If nothing else it affirms why I reload and the #1 reason is to get much more consistent ammo than factory ammo can give me plus the cost difference is definitely a benefit as well.

Have a good weekend and I'm looking forward to Super Bowl 1/2 time commercials tomorrow, the game itself doesn't mean much to me since my team didn't make it. GO NINERS!

 

[Walt Schmidlin]

I believe there was an article about a Palma match 25+ years ago (maybe it was just an international match) where the host country supplied the rifles, ammunition and equipment.
Someone on the USA team had a scale and weight sorted all the ammo that was given to the team since that was the only parameter they could measure.

As I seem to remember the USA team won the match.

Perhaps someone else can fill in the blanks (date, country, people involved).

 

[std7mag]

Powder charges are different for different powders.
If a company can load using 1gr less powder, it adds up to real money after a few thousand cartridges.

 

[Straightshooter1]

Just a few years back I did something similar. I took apart some so called "match grade" .308 ammo after firing 20 of 2 boxes that didn't look good on my target (like around .9 MOA) nor on my chrono with large ES and SD's. When I brought the other box home I started measuring everything to see what kind of variations I would see. The first thing was the bullet concentricity was way off with nothing having a better TIR than .004 and a few as much as .007 - 008 TIR. Seating depth variance was ~.004". Pulled and measure the bullets and they were all with small and acceptable variations for OAL and weight. Next, I weight each cartridge's powder and found a substantial variation in weight, like at .7 gr. Primer seating was pretty good and I didn't bother removing them and case length was ok.

After all these measurements, I also weighed all the powder and divided that total weight by the number of cases, then filled each case with that average weight so that every cartridge had the same charge weight of that powder. I then reassembled the cartridges to a unform SAAMI specs (like COAL at 2.800) and the bullet runouts were .002" TIR or better. When I fired these reassembled cartridges at the range, I got 5 shot groups between .5 and .6 MOA . . . way better than the previous loads of the same lot.

 

[Ringostar]

Have a good weekend and I'm looking forward to Super Bowl 1/2 time commercials tomorrow, the game itself doesn't mean much to me since my team didn't make it. GO NINERS!

Do you know why Iowa doesn’t have a pro football team? Because, if they got one, then Illinois would want one too! Yes, that a cut on the Bears joke.

 

[drop_point]

Bullets, cases, powder, and primer all have weight variance. How do you know where that variance is coming from?

 

[Doom]

A few years back some of us were working with deconstructing Federal Gold Medal Match 308 rounds, 168 and 175 grain SMK. One of the things that stood out in general was that the loaded rounds in a lot varied less than 1 grain in total weight. I lated obtained a significant amount (~200 pcs) of FGGM brass shot by a local Sheriff's Dept. All one lot. That brass varied by less than one grain. I remember weighting some of the powder in the deconstructed loads and if memory serves me right it varied about 0.2 gr and appeared to be IMR 4064.

 

[Sundown]

Did basically the same thing with 22 RF ammo a few years back. The most accurate ammo turned out to be Federal Utra Match. It had a bullet diameter of a little larger than most others and overall components weight were consistant. Trouble is they don't make Fed Utra Match anymore.

 

[IA_shooter]

Bullets, cases, powder, and primer all have weight variance. How do you know where that variance is coming from?

After weighing tons of bullets and cases and seeing posts about weight variation in primers (which is very small) I can only come to the informed conclusion that the biggest weight differences will be either the brass cases or the powder charge within the case.

 

[IA_shooter]

As a continuation of my boredom, I started a project this morning due to my surprise of the weight variation I was seeing in some 204 Ruger ammo I just got, which was almost 4 grains in variation. That's too much for my personal comfort, so this is what I'm doing today. 250 down, 750 to go. Yes I'm OCD.

I will be deconstructing some of the ammo that is in the 156-157gr range and some that is in the 160+gr range in the near future to weigh powder charges within. I will be marking the foam ammo holder inserts that hold the ammo within the cardboard boxes with the weight ranges and I will do some testing on targets through my chronograph too. It should be interesting to see all of the results from this. I don't even own a 204 Ruger rifle yet, but I have a barrel being shipped to me, so it will be a little while before I do the shooting tests.

 

[Coyotefurharvester]

I weighed 20 new Hornady 204R brass 1.4 gr spread. Weighed 20 new Win 204R from a 200 ct bulk bag, 2.8(1 was a full gr off the spread of the other 1.8 gr). Probably means I need to check a lot more brass to get an actual weight spread, regardless of brand.

 

[Beiruty]

 

[Beiruty]

This is my test for Hornady 6-CrdM primed cases
The majority of load ammo weight variance is in the case.
My powder drop is less +- 0.04 gr with auto drop.
Hornady and Berger bullets are +- 0.5gr or less.
All other variance in weight is in the case.

 

[IA_shooter]

I decided to take apart 5 rounds of the high weights ammo, and 5 of the low weights ammo and these are my findings. Very interesting indeed. Case weights are by FAR the biggest variant which I suppose could translate into case capacity and different corresponding pressures when firing the ammo. It was worth my time IMO. Hope others can find this useful. Thanks for looking guys.

 

[drop_point]

After weighing tons of bullets and cases and seeing posts about weight variation in primers (which is very small) I can only come to the informed conclusion that the biggest weight differences will be either the brass cases or the powder charge within the case.

That primer that weighs 3.7 gr instead of 3.6 gr, gets loaded with a 166 gr bullet that should have been 165 gr. with 44.2 gr. of powder instead of 44.0 gr. of powder in a case that is on the light end of 170.0 gr when the majority fall around 172.5 gr. and you've got a round that weighs the very same as the average, but you've got powder, bullet, and primer on the heavy end of the ES with brass on the light end of the ES.

Then you have to ask where that weight distribution is the brass is? Is it in the case head? In the neck? How much does it affect volume?

Have you proven it to show up on target? To have a change is velocity ES?

 

[IA_shooter]

That primer that weighs 3.7 gr instead of 3.6 gr, gets loaded with a 166 gr bullet that should have been 165 gr. with 44.2 gr. of powder instead of 44.0 gr. of powder in a case that is on the light end of 170.0 gr when the majority fall around 172.5 gr. and you've got a round that weighs the very same as the average, but you've got powder, bullet, and primer on the heavy end of the ES with brass on the light end of the ES.

Then you have to ask where that weight distribution is the brass is? Is it in the case head? In the neck? How much does it affect volume?

Have you proven it to show up on target? To have a change is velocity ES?

I know others have proven those points but I personally have not as far as how it shows up on target or velocities. I'll let people look at the results of my testing and make up their own minds what to do with it if anything.

 

[DiRTY DOG]

I know others have proven those points but I personally have not as far as how it shows up on target or velocities. I'll let people look at the results of my testing and make up their own minds what to do with it if anything.

I've read elsewhere that the vast majority of case weight variation is not from case wall thickness, but instead from the case head specifically rim thickness and groove dimensions which has no effect at all on case volume. Seems logical to me.

 

[IA_shooter]

I've read elsewhere that the vast majority of case weight variation is not from case wall thickness, but instead from the case head specifically rim thickness and groove dimensions which has no effect at all on case volume. Seems logical to me.

I guess the way to check that would be to cut pieces of brass about a fourth of the way up from the bottom, maybe less, and measure the difference in the top the bottom? Maybe I'll find some neat little jig where I can do that and I'll keep this brass set aside and I'll figure it out. Maybe that'll be my project for next weekend.

 

[drop_point]

If you're cutting, you can't guarantee an even removal of material. The true test would be to measure capacity.

 

[Ned Ludd]

I guess the way to check that would be to cut pieces of brass about a fourth of the way up from the bottom, maybe less, and measure the difference in the top the bottom? Maybe I'll find some neat little jig where I can do that and I'll keep this brass set aside and I'll figure it out. Maybe that'll be my project for next weekend.

Save your strength. Extractor grooves and primer pockets in quality brands of brass are quite uniform and do not vary enough to account for the majority of difference typically observed in the case weight of a given population of brass. I have been comparing case water volumes to case weights for years and found there is usually a very good inverse correlation between the two; i.e. as case weight goes up, case volume goes down. I've posted numerous graphs proving that this relationship exists and reached the point where I'm not even going to post such graphs any longer, so you'll simply have to take my word for it or look up some of my older posts.

In reading the OP, I really wasn't clear at all on what you were trying to accomplish by weighing loaded rounds. However, you cleared that up for me nicely in post #14. My take on weighing loaded rounds would be that for anyone using commercial ammunition, it might be of benefit in terms of generating more uniform velocity. The idea would be that because the majority of weight variance in a loaded round is due to variance in case weight, which can be used within reason as a coarse surrogate for case volume, that weight-sorting loaded rounds might allow for reduced ES/SD. That is certainly a testable hypothesis. In fact, I would start using the exact same approach you used with the pulled rounds above; i.e. selecting High/Low weight extremes and measuring velocity from those loaded rounds. In other words, if you cannot detect a reliable difference in velocity between the High/Low extremes, weight sorting to generate more uniform velocity in loaded rounds probably isn't going to work. I would also suggest that you will need to determine velocity using a statistically significant number of High/Low rounds and properly evaluate the results to demonstrate their significance, if any.

For obvious reasons, I would view weighing rounds that had been loaded by hand as wasted effort. It is far too easy to simply weigh and sort the cases prior to loading, and the sorting results should be better without the added weights of the other components involved. In my experience, sorting cases by weight as a surrogate for volume can certainly provide more consistent internal volume. However, the efficacy of this approach as a means to generate more uniform velocity is less clear. The reason for that is likely that in order to reliably detect a change in velocity caused by variance in case volume, the case volume variance (delta) has to be large enough to generate a velocity change that a typical chronograph can reliably measure. What that means is that with relatively small changes in case volume, it may be difficult to reliably detect concurrent changes in velocity because the predicted velocity changes will be small and fall down into the "noise", or below the limit that a typical chronograph can reliably measure. For this reason, it may be that one could actually detect a statistically significant difference in velocity between the High/Low extremes, but nothing closer. In that event, one would have to choose whether it was worth the effort to continue the weight sorting process, or simply accept that they may not able to reliably demonstrate that the sorting process has any effect. It's a personal choice, really. Many of us do things during the reloading process for which we may not reliably be able to demonstrate a beneficial effect. However, we believe they do, so we do them. It's a "glass half full" thing.