Home Forums Hunting & Shooting Ask The Gunwriters Mule Deer. A question about brass weight and powder charges?

I notice on another thread that you occasionally use Lapua brass. I use it almost exclusively in my 7mm-08’s. I know that as a rule it is heavier than most other brass. Example: individually weighed, it is usually about .010 ounces heavier than Remington or Winchester brass. My question is this; how much do you find that you need to reduce your powder charge when hand loading in Lapua brass compared to other offerings? A percentage of 3 or 4 %, less or more. Any info here will be appreciated.

Can't remember switching to Lapua brass after working up a load in lighter brass. But years ago I was handloading for one of my .30-06s, and at the time Remington and Winchester cases were about it for empty cases. The Remington brass was considerably heavier, common back then, and I found it took two grains less of IMR4350 to get the same velocity with 165-grain bullets.

I would suggest that if somebody wants to switch to Lapua cases after working up loads in other brass to:

(1) Weigh the Lapua brass to make sure it actually is heavier. There are a LOT more kinds of brass available these days, and you can't assume that they're all lighter than Lapua.

2) Start with a load 3% below the one used in the lighter brass, and watch the chronograph. When the charge matches the velocity in the lighter brass, it should work well.

FWIW, some years ago I built a 338 Jamison. The brass was made off an RWS metric case. Very heavy. Shortly after that endeavor Remington came out with their 300 RUM (think it is,) using the same basic metric case as the basis, but with their own brass. Remington RUM brass in the 338 Jamison was 17 grains lighter, therefore larger inside powder capacity. I found that 17g lighter was equal to 1gr of the powders I was using. Outside dimensions were the same but the thicker walls and base made a BIG difference. I had to increase the powder charge by one grain to achieve the same velocity through the range of powders I was using.

There is quite a difference between various makes of 308 Winchester cases. There's almost a twenty grain spread between WW and LC cases that I have.

mathman,

Yeah, and even .308 cases of the same brand can surprise you. Have had batches with about the same 20-grain difference with the same headstamp.

One thing that's been happening more in recent years is ammo/component companies having brass made by different manufacturers, but with the ammo/component company's headstamp. This has been going on for a long time, but the trend has increased. As a result, you don't want to assume that X "brand" of brass weighs the same as your last batch of X--which is why I suggested weighing the brass in my post to lastaround. This can prevent real surprises.

John;
Top of the morning to you, I hope that you and Eileen are well and you're getting decent weather.

Not that you need a hearty "Amen" from the north country, but even 40 years ago when I started loading for the .308 I was shocked at the weight difference in cases, some of them with the same headstamp as you've noted.

If I'm not wrong, there was some wild variation in Winchester stamped stuff, but when I looked close it was a slightly different stamp so obviously a different run at least and likely a different factory.

When I started fooling with the .223 a few years back I ended up using picked up range brass as there's buckets of it at our local range. As you've recommended, I sorted first by headstamp, then by weight and so far that's worked well.

All the best to you both.

Dwayne

John and Dwayne, I agree on the variation within a given brand as well.

I had some early Nosler headstamp 308 which I'm convinced was made for them by Federal. I also had some from a few years ago which I'm pretty sure was made by Norma. There was a noticeable difference in weight and neck wall thickness between the two, the suspected Norma being thinner and lighter.

Reduce charges 0.1 grains for a grain of brass weight. a 223 For a 308 about half tha

I doubt that Federal made brass for Nosler. But maybe.

They were the same weight and neck thickness as Federal of the time and had the same headstamp font. They were also soft like the Federal from that time as well.

Yep, you never know which companies might make brass for others.

I know that Norma has sometimes made cases for Lapua, and vice versa. Which is why I had to laugh a little when somebody on the Campfire sold me some Lapua 6mm PPC cases, but threw in some Norma 6mm PPCs, telling me the Norma cases were "junk" but OK for practice. I'd been using Norma 6PPC cases in my benchrest rifle for a couple years, and after uniforming them easily got 5-shot groups under .2". And am still running, them despite my loads (like those of quite a few benchresters) are a little over listed maximums....

Thanks for the replies folks. And John, anytime I start on a new batch of brass I weigh a percentage (probably 20%) and record it for comparison. I have 300 pieces of Lapua that I use in my 7mm-08 and found that when compared to older loads in Remington brass I got the same velocity with 2.0 grains less using Big Game powder. Example: 50.0 gr. in Remington and 48.0 in Lapua. I just wondered if this was a normal occurrence with Lapua brass. If I ever wear out my current supply, I will definitely weigh the new batch. Thanks for your reply.

My Lapua 308s are about ten grains heavier than my Remington cases. Same for your 7mm08 stuff?

I don't worry about it too much. There are a few components to that. First, the cartridges I typically "push" a bit are those which have lower pressure standards yet are housed in strong rifles .. say .257 Roberts in a Kimber 84M. There's a safety margin involved. Second, we must remember the density of brass compared to the density of powder. In other words, it takes a significant change in the weight of the case to change the volume to make as much difference as even a half grain of powder does.

Don't get me wrong, I re-work my loads when I change brands of cases. Even if volume doesn't change, case neck thickness might, flash holes might. I may be pretty aggressive, maybe just one cartridge each a grain apart, but I do want to recheck at least a little bit. And I do want my brass in a batch to be as consistent in weight as I reasonably can.

I would not follow any particular rule of thumb on this, I would test it to be safe.

I'll say that when all was said and done I've never needed to change my load when changing brass for safety reasons and very very seldom for accuracy reasons. Seems like what works .. works .. and what doesn't, doesn't. My .257 Roberts loads came out the same whether the brass was R-P std brass or WW +P or Nosler +P. Same for .223 .. the only change I had to make with .223 was adjusting the sizing die differently shooting Federal vs WW. It seemed that the WW would "spring back" after a shoulder bump but the Federal was softer, "dead", and it would not spring back so I wound up with headspace issues with Federal brass when my FL die was set up for WW. YMMV of course.

Tom

Mathman,
Checking my notes to be sure, I find that the same is pretty much true with 7mm-08. My older Remington brass (which had been trimmed when weighed) weighed in at 162 grains while the untrimmed Lapua weighed 174 grains. I’m sure trimming the Remington brass made a slight weight difference.

That's right on the money with my 308 stuff.

TOM,

I did experience heavier brass causing a pressure problem relatively early in my "serious" handloading career, when I worked up a load in the .257 Roberts with 100-grain bullets and IMR4350 that exceeded all published data by a grain or two. Used Winchester brass, and when it started to wear out due to cracked necks, I bought some more.

However, I did not notice one small detail about the brass, and the very first round with the same powder charge, from the same 8-pounder of IMR4350, blew the same primer. This was when SAAMI decided to create two categories of pressure for the .257, what might be called "standard" and +P. That said, the +P Maximum Average Pressure standard isn't all that high, 58,000 PSI--which is less than the .30-06's MAP of 60,000, and far less than the .270's 65,000.

However, what Winchester apparently decided was they needed to make +P .257 brass much heavier--which is pretty irrelevant, since brass is not the major factor in withstanding higher pressures. I hadn't weighed the new batch of Winchester brass, assuming it was close enough in weight. It wasn't--and I doubt the substantial extra pressure was due to any difference in flash-holes.

Ran an relatively recent experiment on flash-hole size, due to 6.5 Grendel brass coming in two different primer-sizes, both Large Rifle and Small Rifle, and the small-rifle brass also has the small-rifle flash-hole, which is substantially smaller. Had both kinds of brass, which were two different brands but weighed almost exactly the same, with only .2 grain difference in average weight. I tried three different loads in both cases, and the difference in average velocity was 7, 5 and 8 fps--which statistically is nothing.

And yes, like Buford Boone mentioned, I have found muzzle velocity to be an excellent indicator of relative pressure, as I've mentioned several times in my articles and books over the years. A lot of this comes from an experiment done at the Western Powders piezo pressure-lab around 15 years ago. I worked up loads in three different cartridges, using the standard "pressure signs" many handloaders still tend to use--difficulty in opening the action, primer flatness, case-head marks, and case-head expansion. When pressure-tested at the lab, one load was just about right, one was way over-pressure, and one was way under-pressure. The ONLY reliable indication of relative pressure, aside from the lab-tests, was muzzle velocity. (I also concluded that any of the standard "pressure signs" don't usually show up until pressure's around 70,000 PSI, which is 5000 PSI over the maximum SAAMI pressure listed for any cartridge.)

All of this is one of several reasons I always weigh new brass when starting a handloading project, especially when using more than one brand of brass.

You are very knowledgeable is this aera and I for one respect that and always look forward to you posts or writings on reloading and pressures

jwp475;
Morning sir, I hope you're well and the day's behaving for you.

Thanks for the post, I couldn't agree with you more.

For me there's seldom been a time when I've had a question about what the chronograph readings vs the apparent pressure vs the accuracy of a given load wasn't covered by something John has covered in his writings.

He has an enquiring mind for sure or at least he's consistently answered questions that have come up for me.

Also I've appreciated his candor more than once in giving me some advice on loads or even not that long ago suggesting my chronograph needed replacing. As it turned out, it surely did as it had gone the way of most Canadian politicians and could not be trusted to tell the truth.

All the best and thanks again.

Dwayne

The density of brass is about 8.5 times that of the water typically used to measure a case's capacity. If a case weighs 8.5 gr more than another, then up to 1 gr of water is removed from the chamber.

The trick is knowing where the extra brass is. If the extra brass shows up as a wider rim, or a narrower extractor groove, then that portion is outside the combustion chamber and has no effect. If it's all in the case walls, then you lose that much capacity.

It's best to assume it's in the case walls, so to keep your pressure from rising, adjust your loading density to match. If the net case capacity (below the bullet) is 50 gr of water, and if your case is 8.5 gr heavier, then your net capacity might end up only 49 gr of water. This is a 2% drop in net capacity, so drop your charge by 2%. This should lower your pressure slightly, though.

As for the chronograph, a ballistic rule of thumb is a 4% drop in net capacity will, for a given pressure, cost you only a little over 1% in muzzle velocity. (This is a result of the changes to the expansion ratio and the charge to bullet mass ratio.)

In your situation, there's around 48 gr of net case capacity, and 0.010 oz of brass is only about 0.5 gr of water, or 1%. In a modern bolt action, it's not something to worry about unless your charges are beyond max. If you're into long range target shooting, the resulting small changes in fps might be a concern, of course.